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Background: Environmental soil contamination is a serious problem for humans worldwide, as it causes many diseases. Methods: The present study focuses on utilizing biosurfactants produced by Pseudomonas stutzeri (P. stutzeri) NA3 and Bacillus cereus (B. cereus) EN6, as an electrolyte for removing chromium (Cr) from contaminated soil using the electrokinetic (EK) process. Results: As a result, biosurfactants produced by P. stutzeri NA3 and B. cereus EN6, being lipopeptides, increase heavy metal mobility in the EK process. The Cr removal efficiency of a novel electrolyte (biosurfactants) in the EK process was compared with that of NA3 and EN6 biosurfactants. The EK results revealed a maximum Cr removal of 75 and 70% by NA3 and EN6, respectively, at the end of 7 days. Discussion: The biosurfactant aids in the breaking down of the heavy metals that are present deeper into the soil matrix. From the metagenomics analysis, it was identified that biosurfactant changes the microbial community with an enhanced ability to remove heavy metals. The phytotoxicity assay confirms that NA3 biosurfactant solution showed 95% seed germination and can lower hazardous pollutants in the soil. Conclusion: The application of biosurfactants as a potent electrolyte for the remediation of hazardous pollutants is an integrated process. Overall, the results of this study suggest that biosurfactants can serve as an economic and efficient electrolyte in the EK process to remove Cr from polluted soil. [ABSTRACT FROM AUTHOR]

Soil microbial inoculants are widely recognized as an environmentally friendly strategy for promoting crop growth and increasing productivity. However, research on utilizing the microbial resources from desert biological soil crusts to enhance crop growth remains relatively unexplored. In the present work, a bacterial strain designated AC1-8 with high levels of amylase, protease, and cellulase activity was isolated from cyanobacterial crusts of the Tengger Desert and identified as Bacillus cereus (CGMCC 1.60196). The refinement of the fermentation parameters of B. cereus CGMCC 1.60196 determined that the most effective medium for biomass production was composed of 5 g/L glucose, 22 g/L yeast extract and 15 g/L MgSO4, and the optimal culture conditions were pH 6.0, temperature 37°C, inoculation quantity 3% and agitation speed 240 rpm. Furthermore, the utilization of B. cereus CGMCC 1.60196 has resulted in substantial improvements in various growth parameters of maize seedlings, including shoot length, shoot fresh and dry weights, root fresh and dry weights, and the contents of chlorophyll a, chlorophyll b, and total chlorophyll. The most pronounced growth promotion was observed at an application concentration of 1 × 109 CFU/m2. These results suggest that the novel B. cereus strain, isolated from cyanobacterial crusts, can be regarded as an exemplary biological agent for soil improvement, capable of enhancing soil conditions, promoting crop cultivation and supporting food production. [ABSTRACT FROM AUTHOR]

Kombucha, a beverage traditionally obtained through the fermentation of tea, is believed to have beneficial health properties. Therefore, characterizing the microorganisms responsible for this fermentation is essential to demonstrate its potential health benefits and to identify candidates for new probiotics. In this study, four probiotic yeast strains isolated from kombucha tea were identified, by the PCR-RFLP analysis of the ribosomal ITS region and the sequence of the D1/D2 domain of the 26S rDNA, as Brettanomyces bruxellensis (UVI55 and UVI56) and B. anomalus (UVI57 and UVI58). Properties relevant to probiotics were also studied in these strains. All of them showed excellent survival in simulated gastric (99%-100%) and duodenal (95%-100%) juices. The ability to self-aggregate (38%-100%), adhesion to xylene (15%-50%) and, above all, adhesion to Caco-2 cells (4%-21%), revealed its potential capacity to adhere to the intestinal epithelium. In addition, the tested strains showed excellent antioxidant capacity (82%-94%), antimicrobial activity against different pathogens (Escherichia coli, Staphylococcus aureus, Salmonella enterica, Listeria monocytogenes, and Bacillus cereus), as well as remarkable cytotoxic activity against colon, melanoma and ovarian tumor cell lines. Finally, using Caenorhabditis elegans as a model, strain UVI56 exhibited ability to both extend the lifespan of the nematode and protect it against infection by S. enterica. These results support the probiotic and functional properties of the analyzed strains. In conclusion, the study revealed that kombucha tea could be a source of potential probiotics that contribute to its health-promoting properties and that the characterized Brettanomyces strains could be exploited directly as probiotics or for the development of new functional foods. [ABSTRACT FROM AUTHOR]

The alarming rise in antimicrobial resistance (AMR) has created a significant public health challenge, necessitating the discovery of new therapeutic agents to combat infectious diseases and oxidative stress-related disorders. The Lentzea flaviverrucosa strain E25-2, isolated from Moroccan forest soil, represents a potential avenue for such research. This study aimed to identify the isolate E25-2, obtained from soil in a cold Moroccan ecosystem, and further investigate its antimicrobial and antioxidant activities. Phylogenetic analysis based on 16S rRNA gene sequences revealed the strain's classification within the Lentzea genus, with a sequence closely resembling that of Lentzea flaviverrucosa AS4.0578 (96.10% similarity). Antimicrobial activity in solid media showed moderate to strong activity against Staphylococcus aureus ATCC 25923, Bacillus cereus strain ATCC 14579, Escherichia coli strain ATCC 25922, Candida albicans strain ATCC 60193 and 4 phytopathogenic fungi. In addition, ethyl acetate extract of this isolate demonstrated potent antimicrobial activity against 7 clinically multi-drug resistant bacteria. Furthermore, it demonstrated antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radicals, as well as a significant increase in ferric reducing antioxidant power. A significant positive correlation was observed between antioxidant activities and total content of phenolic compounds (p < 0.0001), along with flavonoids (p < 0.0001). Furthermore, gas chromatography-mass spectrometry (GC-MS) analysis revealed the presence of amines, hydroxyl groups, pyridopyrazinone rings, esters and pyrrolopyrazines. The Lentzea genus could offer promising prospects in the fight against antibiotic resistance and in the prevention against oxidative stress related diseases. [ABSTRACT FROM AUTHOR]

Edible grasshopper, Ruspolia ruspolia, has nutritional and cherished cultural and economic importance to people from diverse cultures, particularly in over 20 African countries. It is consumed at home or commercially traded as sautéed, deep-fried, or boiled products. However, there is limited information on the hygiene practices of the vendors and the implications on the microbial safety of the final product. This research aimed at assessing the food safety knowledge, handling practices and shelf life of edible long-horned grasshopper products among vendors and the microbial safety of ready-to-eat products sold in 12 different markets in Uganda. Samples of raw, deep-fried and boiled grasshoppers were randomly collected from 74 vendors (62% street and 38% market vendors) and subjected to microbial analysis. Over 85% of the vendors surveyed had no public health food handler's certificate and >95% had limited post-harvest handling knowledge. Total aerobic bacteria (7.30-10.49 Log10 cfu/g), Enterobacteriaceae (5.53-8.56 Log10 cfu/g), yeasts andmolds (4.96-6.01 Log10 cfu/g) total counts were significantly high and above the acceptable Codex Alimentarius Commission and Food Safety Authority of Ireland (FSAI) limits for ready-to-eat food products. Eight key pathogenic bacteria responsible for foodborne diseases were detected and these isolates were characterized as Bacillus cereus, Hafnia alvei, Serratia marcescens, Staphylococcus aureus, S. xylosus, S. scuiri, S. haemolyticus, and Pseudomonas aeruginosa. Findings from this study highlight the urgent need to create local and national food safety policies for the edible grasshopper "nsenene" subsector to regulate and guide street and market vending along the value chain, to prevent the transmission of foodborne diseases to consumers. [ABSTRACT FROM AUTHOR]

Contamination of vegetables with human pathogenic microorganisms (HPMOs) is considered one of the most important problems in the food industry, as current nutritional guidelines include increased consumption of raw or minimally processed organic vegetables due to healthy lifestyle promotion. Vegetables are known to be potential vehicles for HPMOs and sources of disease outbreaks. In this study, we tested the susceptibility of radish (Raphanus sativus) to colonization by different HPMOs, including Escherichia coli PCM 2561, Salmonella enterica subsp. enterica PCM 2565, Listeria monocytogenes PCM 2191 and Bacillus cereus PCM 1948. We hypothesized that host plant roots containing bactericidal compounds are less prone to HPMO colonization than shoots and leaves. We also determined the effect of selected pathogens on radish growth to check host plant--microbe interactions. We found that oneweek- old radish is susceptible to colonization by selected HPMOs, as the presence of the tested HPMOs was demonstrated in all organs of R. sativus. The differences were noticed 2 weeks after inoculation because B. cereus was most abundant in roots (log10 CFU -- 2.54), S. enterica was observed exclusively in stems (log10 CFU -- 3.15), and L. monocytogenes and E. coli were most abundant in leaves (log10 CFU -- 4.80 and 3.23, respectively). The results suggest that E. coli and L. monocytogenes show a higher ability to colonize and move across the plant than B. cereus and S. enterica. Based on fluorescence in situ hybridization (FISH) and confocal laser scanning microscopy (CLSM) approach HPMOs were detected in extracellular matrix and in some individual cells of all analyzed organs. The presence of pathogens adversely affected the growth parameters of one-week-old R. sativus, especially leaf and stem fresh weight (decreased by 47--66 and 17--57%, respectively). In two-week-old plants, no reduction in plant biomass development was noted. This observation may result from plant adaptation to biotic stress caused by the presence of HPMOs, but confirmation of this assumption is needed. Among the investigated HPMOs, L. monocytogenes turned out to be the pathogen that most intensively colonized the aboveground part of R. sativus and at the same time negatively affected the largest number of radish growth parameters. [ABSTRACT FROM AUTHOR]

Introduction: Bacillus cereus is a ubiquitous opportunistic human pathogen that causes food intoxications worldwide. However, the genomic characteristics and pathogenic mechanisms of B. cereus are still unclear. Methods: Here, we isolated and purified nine strains of B. cereus (LY01-LY09) that caused vomiting, diarrhea and other symptoms from four foodborne outbreaks happened in Guizhou Province in southwest China from June to September 2021. After colony observation, Gram staining, microscopic examination and biochemical test, they were identified as B. cereus. The genomic characteristics, phylogenetic relationships and virulence factors of the isolated strains were analyzed at the genome level. Genome sequencing, comparative genomic analysis, secondary metabolite analysis and quantitative PCR were utilized to give a thorough exploration of the strains. Results:We obtained the genome maps of LY01-LY09 and found that LY01-LY09 had a complex interspecific relationship with B. anthracis and B. thuringiensis. We also observed a contraction of gene families in LY01-LY09, and the contracted families were mainly associated with prophage, which contributed to the species diversity of B. cereus. The Hsp20 gene family underwent a rapid evolution in LY01-LY09, which facilitated the adaptation of the strains to adverse environmental conditions. Moreover, the LY01-LY09 strains exhibited a higher copy number in the non-ribosomal polypeptide synthetase (NRPS) genes and carried the complete cereulide synthetase (ces) gene cluster sequences. Considering that the NRPS system is a classical regulatory mechanism for emetic toxin synthesis, we hypothesized that LY01-LY09 could synthesize emetic toxins through the regulation of ces gene clusters by the NRPS system. Discussion: These findings are important for further investigation into the evolutionary relationship between B. cereus and their related species, as well as the underlying mechanisms governing the synthesis and secretion of bacterial toxins. [ABSTRACT FROM AUTHOR]

Introduction: This study examines the optimum conversion of Wuzhishan pig manure by Black Soldier Fly Larvae (BSFL) at various phases of development, as well as the impact of gut microbiota on conversion efficiency. Method and results: In terms of conversion efficiency, BSFL outperformed the growing pig stage (GP) group, with significantly higher survival rates (96.75%), fresh weight (0.23 g), and larval conversion rate (19.96%) compared to the other groups. Notably, the GP group showed significant dry matter reductions (43.27%) and improved feed conversion rates (2.17). Nutritional composition varied, with the GP group having a lower organic carbon content. High throughput 16S rRNA sequencing revealed unique profiles, with the GP group exhibiting an excess of Lactobacillus and Clostridium. Promising cellulose-degrading bacteria in pig manure and BSFL intestines, including Bacillus cereus and Bacillus subtilis, showed superior cellulose degradation capabilities. The synergy of these thermophilic bacteria with BSFL greatly increased conversion efficiency. The BSFL1-10 group demonstrated high growth and conversion efficiency under specific conditions, with remarkable larval moisture content (71.11%), residual moisture content (63.20%), and waste reduction rate (42.28%). Discussion: This study sheds light on the optimal stages for BSFL conversion of pig manure, gut microbiota dynamics, promising thermophilic cellulosedegrading bacteria, and the significant enhancement of efficiency through synergistic interactions. These findings hold great potential for sustainable waste management and efficient biomass conversion, contributing to environmental preservation and resource recovery. [ABSTRACT FROM AUTHOR]

Planetary protection is a guiding principle aiming to prevent microbial contamination of the solar system by spacecraft (forward contamination) and extraterrestrial contamination of the Earth (backward contamination). Bioburden reduction on spacecraft, including cruise and landing systems, is required to prevent microbial contamination from Earth during space exploration missions. Several sterilization methods are available; however, selecting appropriate methods is essential to eliminate a broad spectrum of microorganisms without damaging spacecraft components during manufacturing and assembly. Here, we compared the effects of different bioburden reduction techniques, including dry heat, UV light, isopropyl alcohol (IPA), hydrogen peroxide (H2O2), vaporized hydrogen peroxide (VHP), and oxygen and argon plasma on microorganisms with different resistance capacities. These microorganisms included Bacillus atrophaeus spores and Aspergillus niger spores, Deinococcus radiodurans, and Brevundimonas diminuta, all important microorganisms for considering planetary protection. Bacillus atrophaeus spores showed the highest resistance to dry heat but could be reliably sterilized (i.e., under detection limit) through extended time or increased temperature. Aspergillus niger spores and D. radiodurans were highly resistant to UV light. Seventy percent of IPA and 7.5% of H2O2 treatments effectively sterilized D. radiodurans and B. diminuta but showed no immediate bactericidal effect against B. atrophaeus spores. IPA immediately sterilized A. niger spores, but H2O2 did not. During VHP treatment under reduced pressure, viable B. atrophaeus spores and A. niger spores were quickly reduced by approximately two log orders. Oxygen plasma sterilized D. radiodurans but did not eliminate B. atrophaeus spores. In contrast, argon plasma sterilized B. atrophaeus but not D. radiodurans. Therefore, dry heat could be used for heat-resistant component bioburden reduction, and VHP or plasma for non-heat-resistant components in bulk bioburden reduction. Furthermore, IPA, H2O2, or UV could be used for additional surface bioburden reduction during assembly and testing. The systemic comparison of sterilization efficiencies under identical experimental conditions in this study provides basic criteria for determining which sterilization techniques should be selected during bioburden reduction for forward planetary protection. [ABSTRACT FROM AUTHOR]

The soil-dwelling delta-proteobacterium Myxococcus xanthus is a model organism to study predation and competition. M. xanthus preys on a broad range of bacteria mediated by lytic enzymes, exopolysaccharides, Type-IV pilus-based motility, and specialized metabolites. Competition between M. xanthus and prey bacterial strains with various specialized metabolite profiles indicates a range of fitness, suggesting that specialized metabolites contribute to prey survival. To expand our understanding of how specialized metabolites affect predator–prey dynamics, we assessed interspecies interactions between M. xanthus and two strains of Bacillus cereus. While strain ATCC 14579 resisted predation, strain T was found to be highly sensitive to M. xanthus predation. The interaction between B. cereus ATCC 14579 and M. xanthus appears to be competitive, resulting in population loss for both predator and prey. Genome analysis revealed that ATCC 14579 belongs to a clade that possesses the biosynthetic gene cluster for production of thiocillins, whereas B. cereus strain T lacks those genes. Further, purified thiocillin protects B. cereus strains unable to produce this specialized metabolite, strengthening the finding that thiocillin protects against predation and contributes to the ecological fitness of B. cereus ATCC 14579. Lastly, strains that produce thiocillin appear to confer some level of protection to their own antibiotic by encoding an additional copy of the L11 ribosomal protein, a known target for thiopeptides. This work highlights the importance of specialized metabolites affecting predator–prey dynamics in soil microenvironments. [ABSTRACT FROM AUTHOR]

Contamination of vegetables with human pathogenic microorganisms (HPMOs) is considered one of the most important problems in the food industry, as current nutritional guidelines include increased consumption of raw or minimally processed organic vegetables due to healthy lifestyle promotion. Vegetables are known to be potential vehicles for HPMOs and sources of disease outbreaks. In this study, we tested the susceptibility of radish (Raphanus sativus) to colonization by different HPMOs, including Escherichia coli PCM 2561, Salmonella enterica subsp. enterica PCM 2565, Listeria monocytogenes PCM 2191 and Bacillus cereus PCM 1948. We hypothesized that host plant roots containing bactericidal compounds are less prone to HPMO colonization than shoots and leaves. We also determined the effect of selected pathogens on radish growth to check host plant–microbe interactions. We found that one-week-old radish is susceptible to colonization by selected HPMOs, as the presence of the tested HPMOs was demonstrated in all organs of R. sativus. The differences were noticed 2 weeks after inoculation because B. cereus was most abundant in roots (log10 CFU – 2.54), S. enterica was observed exclusively in stems (log10 CFU – 3.15), and L. monocytogenes and E. coli were most abundant in leaves (log10 CFU – 4.80 and 3.23, respectively). The results suggest that E. coli and L. monocytogenes show a higher ability to colonize and move across the plant than B. cereus and S. enterica. Based on fluorescence in situ hybridization (FISH) and confocal laser scanning microscopy (CLSM) approach HPMOs were detected in extracellular matrix and in some individual cells of all analyzed organs. The presence of pathogens adversely affected the growth parameters of one-week-old R. sativus, especially leaf and stem fresh weight (decreased by 47–66 and 17–57%, respectively). In two-week-old plants, no reduction in plant biomass development was noted. This observation may result from plant adaptation to biotic stress caused by the presence of HPMOs, but confirmation of this assumption is needed. Among the investigated HPMOs, L. monocytogenes turned out to be the pathogen that most intensively colonized the aboveground part of R. sativus and at the same time negatively affected the largest number of radish growth parameters.

Characterization of the microbiomes of pre-launch spacecraft in spacecraft assembly facilities is an important step in keeping crews healthy during journeys that can last several hundred days in small artificial environments in space. Bacillus cereus, a foodborne pathogenic bacterium, has the potential to be a significant source of food contamination in such environments. This bacterium is a spore-forming bacteria that resists different antimicrobial treatments in cleanrooms where spacecraft are assembled. This study evaluated 41 B. cereus isolates from four pre-launch spacecraft in spacecraft assembly facilities for their toxin gene profile and antibiotic resistance. Four enterotoxin genes (hlbC, cytK, nheA, and entFM) and two emetic toxin genes (ces and CER) were targeted for chromosomal DNA and plasmid DNA. Results showed 31.7, 7.3, 85, and 41.5% of isolates contained hblC, cytK, nheA, and entFM, respectively, in chromosomal or plasmid DNA. Overall, 37 isolates (90.2%) showed at least one enterotoxin gene. The emetic toxin gene, ces, was detected in the plasmid DNA of three isolates (7.3%). The antibiotic resistance of isolates was evaluated by the Kirby-Bauer disk diffusion procedure. All the isolates exhibited 100% susceptibility to gentamicin, 97% were susceptible to clindamycin, and 95% to chloramphenicol, imipenem, tetracycline, and vancomycin. The overall susceptibility average is 51%. However, 98% of the isolates were resistant to β-lactam antibiotics, 97.5% were resistant to sulfamethoxazole/trimethoprim, and 80% were resistant to rifampin. This study provides important information on B. cereus isolates from spacecraft assembly facilities for use in microbial monitoring programs of spacecraft. [ABSTRACT FROM AUTHOR]

Lactoferrin is an iron-binding glycoprotein exhibiting antibacterial, antiviral, antifungal, antiparasitic, antiinflammatory, antianaemic and anticarcinogenic properties. While its inhibitory effects against bacterial pathogens are well investigated, little is known about its influence on the production and/or mode of action of bacterial toxins. Thus, the present study aimed to determine the impact of food supplements based on bovine lactoferrin on Bacillus cereus enterotoxin production. First, strain-specific growth inhibition of three representative isolates was observed in minimal medium with 1 or 10 mg/mL of a lactoferrin-based food supplement, designated as product no. 1. Growth inhibition did not result from iron deficiency. In contrast to that, all three strains showed increased amounts of enterotoxin component NheB in the supernatant, which corresponded with cytotoxicity. Moreover, lactoferrin product no. 1 enhanced NheB production of further 20 out of 28 B. cereus and Bacillus thuringiensis strains. These findings again suggested a strain-specific response toward lactoferrin. Product-specific differences also became apparent comparing the influence of further six products on highly responsive strain INRA C3. Highest toxin titres were detected after exposure to products no. 7, 1 and 2, containing no ingredients except pure bovine lactoferrin. INRA C3 was also used to determine the transcriptional response toward lactoferrin exposure via RNA sequencing. As control, iron-free medium was also included, which resulted in down-regulation of eight genes, mainly involved in amino acid metabolism, and in up-regulation of 52 genes, mainly involved in iron transport, uptake and utilization. In contrast to that, 153 genes were down-regulated in the presence of lactoferrin, including genes involved in flagellar assembly, motility, chemotaxis and sporulation as well as genes encoding regulatory proteins, transporters, heat and cold shock proteins and virulence factors. Furthermore, 125 genes were up-regulated in the presence of lactoferrin, comprising genes involved in sporulation and germination, nutrient uptake, iron transport and utilization, and resistance. In summary, lactoferrin exposure of B. cereus strain-specifically triggers an extensive transcriptional response that considerably exceeds the response toward iron deficiency and, despite downregulation of various genes belonging to the PlcR-regulon, ultimately leads to an increased level of secreted enterotoxin by a mechanism, which has yet to be elucidated. [ABSTRACT FROM AUTHOR]

Introduction: Bacillus licheniformis (B. licheniformis) is a microorganism with a wide range of probiotic properties and applications. Isolation and identification of novel strains is a major aspect of microbial research. Besides, different carbon sources have varying effects on B. licheniformis in regulating the microenvironment, and these mechanisms need to be investigated further. Methods: In this study, we isolated and identified a new strain of B. licheniformis from bovine rumen fluid and named it B. licheniformis NXU98. The strain was treated with two distinct carbon sources--microcrystalline cellulose (MC) and cellobiose (CB). A combination of transcriptome and proteome analyses was used to investigate different carbon source effects. Results: The results showed that B. licheniformis NXU98 ABC transporter proteins, antibiotic synthesis, flagellar assembly, cellulase-related pathways, and proteins were significantly upregulated in the MC treatment compared to the CB treatment, and lactate metabolism was inhibited. In addition, we used MC as a distinct carbon source to enhance the antibacterial ability of B. licheniformis NXU98, to improve its disease resistance, and to regulate the rumen microenvironment. Discussion: Our research provides a potential new probiotic for feed research and a theoretical basis for investigating the mechanisms by which bacteria respond to different carbon sources. [ABSTRACT FROM AUTHOR]

Introduction: Although Bacillus species have produced a wide variety of structurally diverse and biologically active natural products, the secondary biosynthetic potential of Bacillus species is widely underestimated due to the limited number of biosynthetic gene clusters (BGCs) in this genus. The significant variation in the diversity and novelty of BGCs across different species within the Bacillus genus presents a major obstacle to the efficient discovery of novel natural products from Bacillus. Methods: In this study, the number of each class of BGCs in all 6,378 high-quality Bacillus genomes was predicted using antiSMASH, the species-specificity of BGC distribution in Bacillus was investigated by Principal component analysis. Then the structural diversity and novelty of the predicted secondary metabolites in Bacillus species with specific BGC distributions were analyzed using molecular networking. Results: Our results revealed a certain degree of species-specificity in the distribution of BGCs in Bacillus, which was mainly contributed by siderophore, type III polyketide synthase (T3PKS), and transAT-PKS BGCs. B. wiedmannii, B. thuringiensis, and B. cereus are rich in RiPP-like and siderophore BGCs, but lack T3PKS BGCs, while B. amyloliquefaciens and B. velezensis are abundant in transAT-PKS BGCs. These Bacillus species collectively encode 77,541 BGCs, with NRPS and RiPPs being the two most dominant types, which are further categorized into 4,291 GCFs. Remarkably, approximately 54.5% of GCFs and 93.8% of the predicted metabolite scaffolds are found exclusively in a single Bacillus species. Notably, B. cereus, B. thuringiensis, and B. velezensis exhibit the highest potential for producing species-specific NRPS and PKS bioinformatic natural products. Taking two species-specific NRPS gene clusters as examples, the potential of Bacillus to synthesize novel species-specific natural products is illustrated. Conclusion: This study highlights the species-specificity of the secondary biosynthetic potential in Bacillus and provides valuable insights for the targeted discovery of novel natural products from this genus. [ABSTRACT FROM AUTHOR]

Bacillus cereus sensu lato (Bcsl) strains are widely explored due to their capacity to antagonize a broad range of plant pathogens. These include B. cereus sp. UW85, whose antagonistic capacity is attributed to the secondary metabolite Zwittermicin A (ZwA). We recently isolated four soil and root-associated Bcsl strains (MO2, S-10, S-25, LSTW-24) that displayed different growth profiles and in-vitro antagonistic effects against three soilborne plant pathogens models: Pythium aphanidermatum (oomycete) Rhizoctonia solani (basidiomycete), and Fusarium oxysporum (ascomycete). To identify genetic mechanisms potentially responsible for the differences in growth and antagonistic phenotypes of these Bcsl strains, we sequenced and compared their genomes, and that of strain UW85 using a hybrid sequencing pipeline. Despite similarities, specific Bcsl strains had unique secondary metabolite and chitinase-encoding genes that could potentially explain observed differences in in-vitro chitinolytic potential and anti-fungal activity. Strains UW85, S-10 and S-25 contained a (~500 Kbp) mega-plasmid that harbored the ZwA biosynthetic gene cluster. The UW85 mega-plasmid contained more ABC transporters than the other two strains, whereas the S-25 mega-plasmid carried a unique cluster containing cellulose and chitin degrading genes. Collectively, comparative genomics revealed several mechanisms that can potentially explain differences in in-vitro antagonism of Bcsl strains toward fungal plant pathogens. [ABSTRACT FROM AUTHOR]

Characterization of the microbiomes of pre-launch spacecraft in spacecraft assembly facilities is an important step in keeping crews healthy during journeys that can last several hundred days in small artificial environments in space. Bacillus cereus, a foodborne pathogenic bacterium, has the potential to be a significant source of food contamination in such environments. This bacterium is a spore-forming bacteria that resists different antimicrobial treatments in cleanrooms where spacecraft are assembled. This study evaluated 41 B. cereus isolates from four pre-launch spacecraft in spacecraft assembly facilities for their toxin gene profile and antibiotic resistance. Four enterotoxin genes (hlbC, cytK, nheA, and entFM) and two emetic toxin genes (ces and CER) were targeted for chromosomal DNA and plasmid DNA. Results showed 31.7, 7.3, 85, and 41.5% of isolates contained hblC, cytK, nheA, and entFM, respectively, in chromosomal or plasmid DNA. Overall, 37 isolates (90.2%) showed at least one enterotoxin gene. The emetic toxin gene, ces, was detected in the plasmid DNA of three isolates (7.3%). The antibiotic resistance of isolates was evaluated by the Kirby-Bauer disk diffusion procedure. All the isolates exhibited 100% susceptibility to gentamicin, 97% were susceptible to clindamycin, and 95% to chloramphenicol, imipenem, tetracycline, and vancomycin. The overall susceptibility average is 51%. However, 98% of the isolates were resistant to β-lactam antibiotics, 97.5% were resistant to sulfamethoxazole/trimethoprim, and 80% were resistant to rifampin. This study provides important information on B. cereus isolates from spacecraft assembly facilities for use in microbial monitoring programs of spacecraft.

Lactoferrin is an iron-binding glycoprotein exhibiting antibacterial, antiviral, antifungal, antiparasitic, antiinflammatory, antianaemic and anticarcinogenic properties. While its inhibitory effects against bacterial pathogens are well investigated, little is known about its influence on the production and/or mode of action of bacterial toxins. Thus, the present study aimed to determine the impact of food supplements based on bovine lactoferrin on Bacillus cereus enterotoxin production. First, strain-specific growth inhibition of three representative isolates was observed in minimal medium with 1 or 10 mg/mL of a lactoferrin-based food supplement, designated as product no. 1. Growth inhibition did not result from iron deficiency. In contrast to that, all three strains showed increased amounts of enterotoxin component NheB in the supernatant, which corresponded with cytotoxicity. Moreover, lactoferrin product no. 1 enhanced NheB production of further 20 out of 28 B. cereus and Bacillus thuringiensis strains. These findings again suggested a strain-specific response toward lactoferrin. Product-specific differences also became apparent comparing the influence of further six products on highly responsive strain INRA C3. Highest toxin titres were detected after exposure to products no. 7, 1 and 2, containing no ingredients except pure bovine lactoferrin. INRA C3 was also used to determine the transcriptional response toward lactoferrin exposure via RNA sequencing. As control, iron-free medium was also included, which resulted in down-regulation of eight genes, mainly involved in amino acid metabolism, and in up-regulation of 52 genes, mainly involved in iron transport, uptake and utilization. In contrast to that, 153 genes were down-regulated in the presence of lactoferrin, including genes involved in flagellar assembly, motility, chemotaxis and sporulation as well as genes encoding regulatory proteins, transporters, heat and cold shock proteins and virulence factors. Furthermore, 125 genes were up-regulated in the presence of lactoferrin, comprising genes involved in sporulation and germination, nutrient uptake, iron transport and utilization, and resistance. In summary, lactoferrin exposure of B. cereus strain-specifically triggers an extensive transcriptional response that considerably exceeds the response toward iron deficiency and, despite down-regulation of various genes belonging to the PlcR-regulon, ultimately leads to an increased level of secreted enterotoxin by a mechanism, which has yet to be elucidated.

Foodborne diseases as well as Foodborne pathogens are a global issue with significant effects on human health and economy. Therefore, several investigators have tried to find new alternative approaches to prevent and control this problem. In this context, the present study aimed to find some possible and effective approaches for controlling food-borne bacteria via Dill (Anethum graveolens L.) extract (DE) loaded with chitosan nanoparticles (ChNPs) besides its antioxidant and anti-diabetic activities. Flavonoid and phenolic contents of DE were detected by HPLC, indicating the presence of 18 constituents, high content (22526.51 μg/mL) of chlorogenic acid, followed by 2236.21 μg/mL of coumaric acid and 2113.81 μg/mL of pyrocatechol. In contrast, low contents of cinnamic acid, methyl gallate, apigenin, daidzein, quercetin, syringic acid, and kaempferol were detected. B. cereus, Staphylococcus aureus, E. coli, S. typhi, E. faecalis, and C. albicans were highly inhibited by DE loaded ChNPs (DELChNPs) with inhibition zones (IZs) of 28.50 ± 0.87, 30.33 ± 0.58, 29.33 ± 0.58, 23.17 ± 0.76, 25.76 ± 0.58, and 24.17 ± 0.29 mm with MIC 15.41 ± 0.36, 7.70 ± 0.17, 15.58 ± 0.07, 31.08 ± 0.07, 31.04 ± 0.07 and 62.33 ± 0.29 μg/mL compared with inhibitory activity caused by DE, where the IZs were 25.83 ± 1.44, 29.67 ± 0.85, 24.83 ± 0.76, 20.33 ± 1.53, 21.17 ± 0.29, and 19.67 ± 1.15 mm with MIC 62.33 ± 0.29, 31.08 ± 0.07, 62.50 ± 0.29, 31.08 ± 0.07, 31.04 ± 0.07, and 249.0 ± 1.73 μg/mL, respectively. Also, the minimum bactericidal concentration (MBC) of DELChNPs was less than DE against all tested microorganisms. The MBC/MIC index documented that DELChNPs were more effective than DE. The biofilm of tested bacteria was inhibited by DE and DELChNPs but with different levels of anti-biofilm activity. For example, the anti-biofilm activity was 79.26 and 86.15% against B. cereus using DE and DELChNPs, respectively. DELChNPs and DE, compared with the ascorbic acid, exhibited DPPH scavenging % with IC50 values of 7.8 μg/mL, 13.96 μg/mL, and 4.83 μg/mL, respectively. Anti-diabetic activity in vitro via inhibition of amylase indicated that IC50 was 164.2 μg/mL and 164.3 μg/mL using DE and DELChNPs, respectively. This investigation highlights the vital DE phytoconstituents, particularly DELChNPs which possess important therapeutic effects against food-borne microorganisms and could be utilized as a safe alternative to synthetic drugs. [ABSTRACT FROM AUTHOR]

Bacillus cereus is a spore-forming bacterium that occurs as a contaminant in food and feed, occasionally resulting in food poisoning through the production of various toxins. In this study, we retrospectively characterized viable B. cereus sensu lato (s.l.) isolates originating from commercial vitamin B2 feed and food additives collected between 2016 and 2022 by the Belgian Federal Agency for the Safety of the Food Chain from products sold on the Belgian market. In total, 75 collected product samples were cultured on a general medium and, in case of bacterial growth, two isolates per product sample were collected and characterized using whole-genome sequencing (WGS) and subsequently characterized in terms of sequence type (ST), virulence gene profile, antimicrobial resistance (AMR) gene profile, plasmid content, and phylogenomic relationships. Viable B. cereus was identified in 18 of the 75 (24%) tested products, resulting in 36 WGS datasets, which were classified into eleven different STs, with ST165 (n = 10) and ST32 (n = 8) being the most common. All isolates carried multiple genes encoding virulence factors, including cytotoxin K-2 (52.78%) and cereulide (22.22%). Most isolates were predicted to be resistant to beta-lactam antibiotics (100%) and fosfomycin (88.89%), and a subset was predicted to be resistant to streptothricin (30.56%). Phylogenomic analysis revealed that some isolates obtained from different products were closely related or even identical indicating a likely common origin, whereas for some products the two isolates obtained did not show any close relationship to each other or other isolates found in other products. This study reveals that potentially pathogenic and drug-resistant B. cereus s.l. can be present in food and feed vitamin B2 additives that are commercially available, and that more research is warranted to assess whether their presence in these types of products poses a threat to consumers. [ABSTRACT FROM AUTHOR]

Beneficial microorganisms play a pivotal role in the invasion process of exotic plants, including arbuscular mycorrhizal fungi (AMF) and Bacillus. However, limited research exists on the synergistic influence of AMF and Bacillus on the competition between both invasive and native plants. In this study, pot cultures of Ageratina adenophora monoculture, Rabdosia amethystoides monoculture, and A. adenophora and R. amethystoides mixture were used to investigate the effects of dominant AMF (Septoglomus constrictum, SC) and Bacillus cereus (BC), and the co-inoculation of BC and SC on the competitive growth of A. adenophora. The results showed that inoculation with BC, SC, and BC + SC significantly increased the biomass of A. adenophora by 14.77, 112.07, and 197.74%, respectively, in the competitive growth between A. adenophora and R. amethystoides. Additionally, inoculation with BC increased the biomass of R. amethystoides by 185.07%, while inoculation with SC or BC + SC decreased R. amethystoides biomass by 37.31 and 59.70% compared to the uninoculated treatment. Inoculation with BC significantly increased the nutrient contents in the rhizosphere soil of both plants and promoted their growth. Inoculation with SC or SC + BC notably increased the nitrogen and phosphorus contents of A. adenophora, therefore enhancing its competitiveness. Compared with single inoculation, dual inoculation with SC and BC increased AMF colonization rate and Bacillus density, indicating that SC and BC can form a synergistic effect to further enhance the growth and competitiveness of A. adenophora. This study reveals the distinct role of S. constrictum and B. cereus during the invasion of A. adenophora, and provide new clues to the underlying mechanisms of interaction between invasive plant, AMF and Bacillus. [ABSTRACT FROM AUTHOR]

Microbial communities can be considered complex adaptive systems. Understanding how these systems arise from different components and how the dynamics of microbial interactions allow for species coexistence are fundamental questions in ecology. To address these questions, we built a three-species synthetic community, called BARS (Bacillota A+ S+ R). Each species in this community exhibits one of three ecological roles: Antagonistic, Sensitive, or Resistant, assigned in the context of a sediment community. We show that the BARS community reproduces features of complex communities and exhibits higher-order interaction (HOI) dynamics. In paired interactions, the majority of the S species (Sutcliffiella horikoshii 20a) population dies within 5 min when paired with the A species (Bacillus pumilus 145). However, an emergent property appears upon adding the third interactor, as antagonism of species A over S is not observed in the presence of the R species (Bacillus cereus 111). For the paired interaction, within the first 5 min, the surviving population of the S species acquires tolerance to species A, and species A ceases antagonism. This qualitative change reflects endogenous dynamics leading to the expression for tolerance to an antagonistic substance. The stability reached in the triple interaction exhibits a nonlinear response, highly sensitive to the density of the R species. In summary, our HOI model allows the study of the assembly dynamics of a three-species community and evaluating the immediate outcome within a 30min frame. The BARS has features of a complex system where the paired interactions do not predict the community dynamics. The model is amenable to mechanistic dissection and to modeling how the parts integrate to achieve collective properties. [ABSTRACT FROM AUTHOR]

Bacillus cereus G9241 was isolated from a welder who survived a pulmonary anthrax-like disease. Strain G9241 carries two virulence plasmids, pBCX01 and pBC210, as well as an extrachromosomal prophage, pBFH_1. pBCX01 has 99.6% sequence identity to pXO1 carried by Bacillus anthracis and encodes the tripartite anthrax toxin genes and atxA, a mammalian virulence transcriptional regulator. This work looks at how the presence of pBCX01 and temperature may affect the lifestyle of B. cereus G9241 using a transcriptomic analysis and by studying spore formation, an important part of the B. anthracis lifecycle. Here we report that pBCX01 has a stronger effect on gene transcription at the mammalian infection relevant temperature of 37°C in comparison to 25°C. At 37°C, the presence of pBCX01 appears to have a negative effect on genes involved in cell metabolism, including biosynthesis of amino acids, whilst positively affecting the transcription of many transmembrane proteins. The study of spore formation showed B. cereus G9241 sporulated rapidly in comparison to the B. cereus sensu stricto type strain ATCC 14579, particularly at 37°C. The carriage of pBCX01 did not affect this phenotype suggesting that other genetic elements were driving rapid sporulation. An unexpected finding of this study was that pBFH_1 is highly expressed at 37°C in comparison to 25°C and pBFH_1 expression leads to the production of Siphoviridae-like phage particles in the supernatant of B. cereus G9241. This study provides an insight on how the extrachromosomal genetic elements in B. cereus G9241 has an influence in bacterial phenotypes. [ABSTRACT FROM AUTHOR]

This study aimed to isolate and identify a ligninolytic bacterium from the rumen of buffalo (Bubalus bubalis) and investigate its effects as a silage additive for whole-plant rape. Three lignin-degradation strains were isolated from the buffalo rumen, with AH7-7 being chosen for further experiments. Strain AH7-7, with acid tolerance and a 51.4% survival rate at pH 4, was identified as Bacillus cereus. It exhibited a lignin-degradation rate of 20.5% after being inoculated in a lignin-degrading medium for 8 days. We divided the rape into four groups according to the various additive compositions to examine the fermentation quality, nutritional value, and bacterial community after ensiling: Bc group (inoculated with B. cereus AH7-7 3.0 × 106 CFU g FW-1), Blac group (inoculated with B. cereus AH7-7 1.0 × 106 CFU g FW-1, L. plantarum 1.0 × 106 CFU g FW-1, and L. buchneri 1.0 × 106 CFU g FW-1), Lac group (inoculated with L. plantarum 1.5 × 106 CFU g FW-1 and L. buchneri 1.5 × 106 CFU g FW-1), and Ctrl group (no additives). After 60 days of fermentation, the application of B. cereus AH7-7 was potent inmodulating the fermentation quality of silage, especially when combined with L. plantarum and L. buchneri, as indicated by lower dry matter loss and higher contents of crude protein, water-soluble carbohydrate, and lactic acid. Furthermore, treatments with the B. cereus AH7-7 additive decreased the contents of acid detergent lignin, cellulose, and hemicellulose. The B. cereus AH7-7 additive treatments reduced the bacterial diversity and optimized the bacterial community compositions of silage, with an increase in the relative abundance of beneficial Lactobacillus and a decrease in the relative abundance of undesirable Pantoea and Erwinia. Functional prediction revealed that inoculation with B. cereus AH7-7 could increase the cofactors and vitamins metabolism, amino acid metabolism, translation, replication and repair, and nucleotide metabolism, while decreasing the carbohydrate metabolism, membrane transport, and energy metabolism. In brief, B. cereus AH7-7 improved themicrobial community, fermentation activity, and ultimately the quality of silage. The ensiling with B. cereus AH7-7, L. plantarum, and L. buchneri combination is an effective and practical strategy to improve the fermentation and nutrition preservation of rape silage. [ABSTRACT FROM AUTHOR]

2Duf, named after the presence of a transmembrane (TM) Duf421 domain and a small Duf1657 domain in its sequence, is likely located in the inner membrane (IM) of spores in some Bacillus species carrying a transposon with an operon termed spoVA2mob. These spores are known for their extreme resistance to wet heat, and 2Duf is believed to be the primary contributor to this trait. In this study, we found that the absence of YetF or YdfS, both Duf421 domain-containing proteins and found only in wild-type (wt) B. subtilis spores with YetF more abundant, leads to decreased resistance to wet heat and agents that can damage spore core components. The IM phospholipid compositions and core water and calciumdipicolinic acid levels of YetF-deficient spores are similar to those of wt spores, but the deficiency could be restored by ectopic insertion of yetF, and overexpression of YetF increased wt spore resistance to wet heat. In addition, yetF and ydfS spores have decreased germination rates as individuals and populations with germinant receptor-dependent germinants and increased sensitivity to wet heat during germination, potentially due to damage to IM proteins. These data are consistent with a model in which YetF, YdfS and their homologs modify IM structure to reduce IM permeability and stabilize IM proteins against wet heat damage. Multiple yetF homologs are also present in other spore forming Bacilli and Clostridia, and even some asporogenous Firmicutes, but fewer in asporogenous species. The crystal structure of a YetF tetramer lacking the TM helices has been reported and features two distinct globular subdomains in each monomer. Sequence alignment and structure prediction suggest this fold is likely shared by other Duf421-containing proteins, including 2Duf. We have also identified naturally occurring 2duf homologs in some Bacilli and Clostridia species and in wt Bacillus cereus spores, but not in wt B. subtilis. Notably, the genomic organization around the 2duf gene in most of these species is similar to that in spoVA2mob, suggesting that one of these species was the source of the genes on this operon in the extremely wet heat resistant spore formers. [ABSTRACT FROM AUTHOR]

Bacteriophages from the Bastillevirinae subfamily (Herelleviridae family) have proven to be effective against bacteria from the Bacillus genus including organisms from the B. cereus group, which cause food poisoning and persistent contamination of industrial installations. However, successful application of these phages in biocontrol depends on understanding of their biology and stability in different environments. In this study, we isolated a novel virus from garden soil in Wrocław (Poland) and named it 'Thurquoise'. The genome of that phage was sequenced and assembled into a single continuous contig with 226 predicted protein-coding genes and 18 tRNAs. The cryo-electron microscopy revealed that Thurquoise has complex virion structure typical for the Bastillevirinae family. Confirmed hosts include selected bacteria from the Bacillus cereus group-specifically B. thuringiensis (isolation host) and B. mycoides, but susceptible strains display different efficiency of plating (EOP). The eclipse and latent periods of Thurquoise in the isolation host last ~ 50 min and ~ 70 min, respectively. The phage remains viable for more than 8 weeks in variants of the SM buffer with magnesium, calcium, caesium, manganese or potassium and can withstand numerous freeze-thaw cycles if protected by the addition of 15% glycerol or, to a lesser extent, 2% gelatine. Thus, with proper buffer formulation, this virus can be safely stored in common freezers and refrigerators for a considerable time. The Thurquoise phage is the exemplar of a new candidate species within the Caeruleovirus genus in the Bastillevirinae subfamily of the Herelleviridae family with a genome, morphology and biology typical for these taxa. [ABSTRACT FROM AUTHOR]

Bacillus cereus G9241 was isolated from a Louisiana welder suffering from an anthrax-like infection. The organism carries two transcriptional regulators that have previously been proposed to be incompatible with each other in Bacillus anthracis: the pleiotropic transcriptional regulator PlcR found in most members of the Bacillus cereus group but truncated in all B. anthracis isolates, and the anthrax toxin regulator AtxA found in all B. anthracis strains and a few B. cereus sensu stricto strains. Here we report cytotoxic and hemolytic activity of cell free B. cereus G9241 culture supernatants cultured at 25°C to various eukaryotic cells. However, this is not observed at the mammalian infection relevant temperature 37°C, behaving much like the supernatants generated by B. anthracis. Using a combination of genetic and proteomic approaches to understand this unique phenotype, we identified several PlcR-regulated toxins to be secreted highly at 25°C compared to 37°C. Furthermore, results suggest that differential expression of the protease involved in processing the PlcR quorum sensing activator molecule PapR appears to be the limiting step for the production of PlcR-regulated toxins at 37°C, giving rise to the temperature-dependent hemolytic and cytotoxic activity of the culture supernatants. This study provides an insight on how B. cereus G9241 is able to "switch" between B. cereus and B. anthracis-like phenotypes in a temperature-dependent manner, potentially accommodating the activities of both PlcR and AtxA. [ABSTRACT FROM AUTHOR]

Bacillus cereus is a spore-forming bacterium that occurs as a contaminant in food and feed, occasionally resulting in food poisoning through the production of various toxins. In this study, we retrospectively characterized viable B. cereus sensu lato (s.l.) isolates originating from commercial vitamin B2 feed and food additives collected between 2016 and 2022 by the Belgian Federal Agency for the Safety of the Food Chain from products sold on the Belgian market. In total, 75 collected product samples were cultured on a general medium and, in case of bacterial growth, two isolates per product sample were collected and characterized using whole-genome sequencing (WGS) and subsequently characterized in terms of sequence type (ST), virulence gene profile, antimicrobial resistance (AMR) gene profile, plasmid content, and phylogenomic relationships. Viable B. cereus was identified in 18 of the 75 (24%) tested products, resulting in 36 WGS datasets, which were classified into eleven different STs, with ST165 (n = 10) and ST32 (n = 8) being the most common. All isolates carried multiple genes encoding virulence factors, including cytotoxin K-2 (52.78%) and cereulide (22.22%). Most isolates were predicted to be resistant to beta-lactam antibiotics (100%) and fosfomycin (88.89%), and a subset was predicted to be resistant to streptothricin (30.56%). Phylogenomic analysis revealed that some isolates obtained from different products were closely related or even identical indicating a likely common origin, whereas for some products the two isolates obtained did not show any close relationship to each other or other isolates found in other products. This study reveals that potentially pathogenic and drug-resistant B. cereus s.l. can be present in food and feed vitamin B2 additives that are commercially available, and that more research is warranted to assess whether their presence in these types of products poses a threat to consumers.

Bacillus cereus G9241 was isolated from a welder who survived a pulmonary anthrax-like disease. Strain G9241 carries two virulence plasmids, pBCX01 and pBC210, as well as an extrachromosomal prophage, pBFH_1. pBCX01 has 99.6% sequence identity to pXO1 carried by Bacillus anthracis and encodes the tripartite anthrax toxin genes and atxA, a mammalian virulence transcriptional regulator. This work looks at how the presence of pBCX01 and temperature may affect the lifestyle of B. cereus G9241 using a transcriptomic analysis and by studying spore formation, an important part of the B. anthracis lifecycle. Here we report that pBCX01 has a stronger effect on gene transcription at the mammalian infection relevant temperature of 37°C in comparison to 25°C. At 37°C, the presence of pBCX01 appears to have a negative effect on genes involved in cell metabolism, including biosynthesis of amino acids, whilst positively affecting the transcription of many transmembrane proteins. The study of spore formation showed B. cereus G9241 sporulated rapidly in comparison to the B. cereus sensu stricto type strain ATCC 14579, particularly at 37°C. The carriage of pBCX01 did not affect this phenotype suggesting that other genetic elements were driving rapid sporulation. An unexpected finding of this study was that pBFH_1 is highly expressed at 37°C in comparison to 25°C and pBFH_1 expression leads to the production of Siphoviridae-like phage particles in the supernatant of B. cereus G9241. This study provides an insight on how the extrachromosomal genetic elements in B. cereus G9241 has an influence in bacterial phenotypes.

Horizontal gene transfer (HGT) is a major driving force in shaping bacterial communities. Key elements responsible for HGT are conjugation-like events and transmissible plasmids. Conjugative plasmids can promote their own transfer as well as that of co-resident plasmids. Bacillus cereus and relatives harbor a plethora of plasmids, including conjugative plasmids, which are at the heart of the group species differentiation and specification. Since the first report of a conjugation-like event between strains of B. cereus sensu lato (s.l.) 40 years ago, many have studied the potential of plasmid transfer across the group, especially for plasmids encoding major toxins. Over the years, more than 20 plasmids from B. cereus isolates have been reported as conjugative. However, with the increasing number of genomic data available, in silico analyses indicate that more plasmids from B. cereus s.l. genomes present self-transfer potential. B. cereus s.l. bacteria occupy diverse environmental niches, which were mimicked in laboratory conditions to study conjugation-related mechanisms. Laboratory mating conditions remain nonetheless simplistic compared to the complex interactions occurring in natural environments. Given the health, economic and ecological importance of strains of B. cereus s.l., it is of prime importance to consider the impact of conjugation within this bacterial group. [ABSTRACT FROM AUTHOR]

In order to develop strategies for preventing biofilm formation in the dairy industry, a deeper understanding of the interaction between different species during biofilm formation is necessary. Bacterial strains of the P. fluorescens group are known as the most important biofilm-formers on the surface of dairy processing equipment that may attract and/or shelter other spoilage or pathogenic bacteria. The present study used different strains of the P. fluorescens group as background microbiota of milk, and evaluated their interaction with Staphylococcus aureus, Bacillus cereus, Escherichia coli O157:H7, and Salmonella Typhimurium during dual-species biofilm formation on stainless steel surfaces. Two separate scenarios for dual-species biofilms were considered: concurrent inoculation of Pseudomonas and pathogen (CI), and delayed inoculation of pathogen to the pre-formed Pseudomonas biofilm (DI). The gram-positive pathogens used in this study did not form dual-species biofilms with P. fluorescens strains unless they were simultaneously inoculated with Pseudomonas strains. E. coli O157:H7 was able to form dualspecies biofilms with all seven P. fluorescens group strains, both in concurrent (CI) and delayed (DI) inoculation. However, the percentage of contribution varied depending on the P. fluorescens strains and the inoculation scenario. S. Typhimurium contributed to biofilm formation with all seven P. fluorescens group strains under the CI scenario, with varying degrees of contribution. However, under the DI scenario, S. Typhimurium did not contribute to the biofilm formed by three of the seven P. fluorescens group strains. Overall, these are the first results to illustrate that the strains within the P. fluorescens group have significant differences in the formation of mono-or dual-species biofilms with pathogenic bacteria. Furthermore, the possibility of forming dual-species biofilms with pathogens depends on whether the pathogens form the biofilm simultaneously with the P. fluorescens group strains or whether these strains have already formed a biofilm. [ABSTRACT FROM AUTHOR]

The microbiome of soil has a fundamental role in maintaining the health of soil and plants. While the diversity of microbes is one of the most important factors in the environment, little is known about the effects of elevation on the microbiome and the impact of the affected microbiome on plants. The main goal of this study is to expand our knowledge of what happens to the soil bacterial community along an altitudinal gradient and investigate their possibly different impacts on plant growth. Bacteria from soils at various altitudes have been isolated, characterized, and identified by Matrix-Assisted Laser Desorption/lonization-Time of Flight Mass Spectrometry (MALDI-TOF MS) to determine the effects of an elevational gradient on the microbiome and plant growth. Furthermore, their effects have been investigated by isolates assessment on maize, wheat, and canola. Based on our results, higher altitude results in a higher diversity of the microbiome and lower bacteria biomass. Bacillus cereus is found in abundance in arid and semi-arid samples. Interestingly, enhanced diversity in higher altitudes shows similarity in response to environmental stress and tolerates these factors well. Furthermore, the inoculation of these bacteria could enhance the overall growth of plants. We prove that bacterial communities could change their biomass and diversity in response to altitude changes. These indicate evolutionary pressure as these bacteria could tolerate stress factors well and have a better relationship with plants. [ABSTRACT FROM AUTHOR]

Bacillus cereus sensu lato (B. cereus sl) is important spoilage bacteria causing milk structure and flavor changes and is ubiquitous in the environment. This study addresses the biodiversity, toxicity, and proteolytic activity of B. cereus sl from 82 environmental samples and 18 raw bovine milk samples from a dairy farm in the region of Tianjin. In sum, 47 B. cereus sl isolates were characterized through biochemical tests, 16S rRNA gene sequencing, and panC gene analysis. Fourteen sequence types (STs) of B. cereus sl were found in raw bovine milk samples, and five new STs (ST2749, ST2750, ST2751, ST2752, and ST2753) were identified in this study. ST1150 was the dominant ST, associated with fecal, air, drinking water, teat skin, teat cup, and teat dip cup. The results of toxin gene analyses showed that 12.77% and 8.51% of isolates carried hblACD and nheABC operons, respectively. In addition, the detection rate of emetic cesB gene was 21.28%. B. cereus sl demonstrated high spoilage potentials even at 7C, which has the proteolytic activity of 14.32 ± 1.96 µmol of glycine equivalents per ml. Proteolytic activities were significantly (p < 0.05) decreased after the heat treatment. The residual activity of protease produced at 7C was significantly higher than that produced at 25C and 37C after treatment at 121C for 10 s and 135C for 5 s (p < 0.01). Together, the results provide insights into the characteristics of B. cereus sl from farm environment and raw bovine milk and revealed that B. cereus sl contamination should also be monitored in raw milk for ultra-high temperature (UHT) products. This knowledge illustrates that strict cleaningmanagement should be implemented to control B. cereus sl and assure high-quality milk products. [ABSTRACT FROM AUTHOR]

To eliminate the influences of excipients and interference of dead bacterial DNA on the detection of Escherichia coli, Pseudomonas aeruginosa, Salmonella paratyphoid B, and Shigella dysentery in live Bacillus licheniformis capsules, a polymerase chain reaction (PCR) method with high sensitivity and specificity was established. By combining bromide with propidium monoazide (PMA) -real-time quantitative PCR (qPCR) with microporous membrane filtration, excipients were removed, the filtrate was collected, and the bacteria were enriched using the centrifugal method. The optimal PMA working concentration, dark incubation time, and exposure time were determined. Specific E. coli, P. aeruginosa, S. paratyphoid B, and S. dysentery primers were selected to design different probes and a multiplex qPCR reaction system was established. The PMA-qPCR method was verified using different concentrations of dead and live bacteria. This method is efficient and accurate and can be widely applied to the detection of aforementioned pathogenic bacterial strains in live Bacillus licheniformis products. [ABSTRACT FROM AUTHOR]

Soil microbial inoculants are widely recognized as an environmentally friendly strategy for promoting crop growth and increasing productivity. However, research on utilizing the microbial resources from desert biological soil crusts to enhance crop growth remains relatively unexplored. In the present work, a bacterial strain designated AC1-8 with high levels of amylase, protease, and cellulase activity was isolated from cyanobacterial crusts of the Tengger Desert and identified as Bacillus cereus (CGMCC 1.60196). The refinement of the fermentation parameters of B. cereus CGMCC 1.60196 determined that the most effective medium for biomass production was composed of 5 g/L glucose, 22 g/L yeast extract and 15 g/L MgSO 4 , and the optimal culture conditions were pH 6.0, temperature 37°C, inoculation quantity 3% and agitation speed 240 rpm. Furthermore, the utilization of B. cereus CGMCC 1.60196 has resulted in substantial improvements in various growth parameters of maize seedlings, including shoot length, shoot fresh and dry weights, root fresh and dry weights, and the contents of chlorophyll a , chlorophyll b , and total chlorophyll. The most pronounced growth promotion was observed at an application concentration of 1 × 10 9 CFU/m 2 . These results suggest that the novel B. cereus strain, isolated from cyanobacterial crusts, can be regarded as an exemplary biological agent for soil improvement, capable of enhancing soil conditions, promoting crop cultivation and supporting food production., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Zhao, Kang, Zhang, Cui, Xu, Wang, Zhang and Gu.)

Horizontal gene transfer (HGT) is a major driving force in shaping bacterial communities. Key elements responsible for HGT are conjugation-like events and transmissible plasmids. Conjugative plasmids can promote their own transfer as well as that of co-resident plasmids. Bacillus cereus and relatives harbor a plethora of plasmids, including conjugative plasmids, which are at the heart of the group species differentiation and specification. Since the first report of a conjugation-like event between strains of B. cereus sensu lato (s.l.) 40 years ago, many have studied the potential of plasmid transfer across the group, especially for plasmids encoding major toxins. Over the years, more than 20 plasmids from B. cereus isolates have been reported as conjugative. However, with the increasing number of genomic data available, in silico analyses indicate that more plasmids from B. cereus s.l. genomes present self-transfer potential. B. cereus s.l. bacteria occupy diverse environmental niches, which were mimicked in laboratory conditions to study conjugation-related mechanisms. Laboratory mating conditions remain nonetheless simplistic compared to the complex interactions occurring in natural environments. Given the health, economic and ecological importance of strains of B. cereus s.l., it is of prime importance to consider the impact of conjugation within this bacterial group.

In order to develop strategies for preventing biofilm formation in the dairy industry, a deeper understanding of the interaction between different species during biofilm formation is necessary. Bacterial strains of the P. fluorescens group are known as the most important biofilm-formers on the surface of dairy processing equipment that may attract and/or shelter other spoilage or pathogenic bacteria. The present study used different strains of the P. fluorescens group as background microbiota of milk, and evaluated their interaction with Staphylococcus aureus, Bacillus cereus, Escherichia coli O157:H7, and Salmonella Typhimurium during dual-species biofilm formation on stainless steel surfaces. Two separate scenarios for dual-species biofilms were considered: concurrent inoculation of Pseudomonas and pathogen (CI), and delayed inoculation of pathogen to the pre-formed Pseudomonas biofilm (DI). The gram-positive pathogens used in this study did not form dual-species biofilms with P. fluorescens strains unless they were simultaneously inoculated with Pseudomonas strains. E. coli O157:H7 was able to form dual-species biofilms with all seven P. fluorescens group strains, both in concurrent (CI) and delayed (DI) inoculation. However, the percentage of contribution varied depending on the P. fluorescens strains and the inoculation scenario. S. Typhimurium contributed to biofilm formation with all seven P. fluorescens group strains under the CI scenario, with varying degrees of contribution. However, under the DI scenario, S. Typhimurium did not contribute to the biofilm formed by three of the seven P. fluorescens group strains. Overall, these are the first results to illustrate that the strains within the P. fluorescens group have significant differences in the formation of mono-or dual-species biofilms with pathogenic bacteria. Furthermore, the possibility of forming dual-species biofilms with pathogens depends on whether the pathogens form the biofilm simultaneously with the P. fluorescens group strains or whether these strains have already formed a biofilm.

Lettuce wraps are popular in Korean cuisine for their high nutritional value and versatility as healthy additions to multiple dishes. Microbial contamination of lettuce is a major concern, as lettuce is consumed fresh without cooking. Among foodborne pathogens, the spore-forming, facultative anaerobic bacterium, Bacillus cereus is one of the frequently detected pathogen in lettuce in Korea. In this study, we investigated the prevalence and distribution of Bacillus cereus strains in lettuce production farms and further evaluated the enterotoxin gene profiles, antibiotic susceptibility, multidrug resistance pattern, and genetic differences among the B. cereus group isolates. Of the 140 samples isolated from 10 lettuce production farms, 30 samples (21.42%) were positive for B. cereus in which 19 (31.6%) and 10 (23.25%) were from soil and lettuce, respectively. The enterotoxin patterns A (hblCDA, nheABC, entFM, and cytK genes) and B (hblCDA, nheABC, and entFM genes) accounted for 50% and 20% of all the isolates, whereas the emetic gene cesB was not detected in any of the B. cereus group isolates. Antibiotic susceptibility testing of the B. cereus group isolates revealed that all the strains were predominantly resistant to β-lactam antibiotics except imipenem and generally susceptible to most of the non β-lactam antibiotics, including gentamycin, streptomycin, chloramphenicol, and tetracycline. ERIC-PCR and MLST analysis revealed high genetic diversity among the 30 B. cereus group isolates, which belonged to 26 different sequence types (STs) and seven new STs. Moreover, isolates with identical STs exhibited similar patterns of antibiotic resistance and enterotoxin profiles. Results of this study indicate a high prevalence of B. cereus group isolates in lettuce production farms in the Republic of Korea. [ABSTRACT FROM AUTHOR]

Bacillus cereus is a major food-borne bacterial pathogen in the world, which can cause diarrhea and emetic syndrome. This study aimed to reveal the quantitative prevalence of B. cereus in ready-to-eat (RTE) rice products in Eastern China and to gain essential information on the characteristics of B. cereus isolates. A total of 91 out of the 1071 samples were positive for B. cereus. The contamination level of B. cereus in 0.5 % of RTE rice product samples outnumbered 103 CFU/g. The number of B. cereus attained 105-106 CFU/g in one sample. The distribution patterns of virulence genes in B. cereus isolates were identified. 84.6% of the B. cereus isolates had at least one enterotoxin or emetic toxin gene. The predominant pattern was XXV. 9.9% of isolates belonged to it and possessed one enterotoxin gene entFM. The occurrence rate of hblACD and nheABC was 36.3% and 47.3%, respectively. Antimicrobial susceptibility tests revealed a high resistance rate toward penicillin, and 23.1% of the isolates were multidrug resistant. B. cereus isolates were genotyped by using ERIC-PCR. 89 genotypes were determined. The Hunter Gaston Discriminatory Index (HGDI) attained 0.9995. Relationships analysis revealed that Group A B. cereus isolates tended to carry hblA, hblC, hblD, nheA, nheB, and show resistance to penicillin/trimethoprim/sulfamethoxazole. This study was useful for updating the knowledge of the contamination status of B. cereus in RTE rice products in China. [ABSTRACT FROM AUTHOR]

Weizhou Island and Xieyang Island are two large and young volcanic sea islands in the northern part of the South China Sea. In this study, high-throughput sequencing (HTS) of 16S rRNA genes was used to explore the diversity of Actinobacteria in the Weizhou and Xieyang Islands. Moreover, a traditional culture-dependent method was utilized to isolate Actinobacteria, and their antibacterial and cytotoxic activities were detected. The alpha diversity indices (ACE metric) of the overall bacterial communities for the larger island (Weizhou) were higher than those for the smaller island (Xieyang). A beta diversity analysis showed a more dispersive pattern of overall bacterial and actinobacterial communities on a larger island (Weizhou). At the order level, Frankiales, Propionibacteriales, Streptomycetales, Micrococcales, Pseudonocardiales, Micromonosporales, Glycomycetales, Corynebacteriales, and Streptosporangiales were the predominant Actinobacteria. A total of 22.7% of the OTUs shared 88%-95% similarity with some known groups. More interestingly, 15 OTUs formed a distinct and most predominant clade, and shared identities of less than 95% with any known families. This is the first report about this unknown group and their 16S rRNA sequences obtained from volcanic soils. A total of 268 actinobacterial strains were isolated by the culturedependent method. Among them, 55 Streptomyces species were isolated, representing that 76.6% of the total. S. variabilis and S. flavogriseus were the most abundant. Moreover, some rare Actinobacteria were isolated. These included Micromonospora spp., Nocardia spp., Amycolatopsis spp., Tsukamurella spp., Mycobacterium spp., and Nonomuraea spp. Among them, eight Streptomyces spp. exhibited antibacterial activity against Bacillus cereus. Only three strains inhibited the growth of Escherichia coli. Four strains showed good activity against aquatic pathogenic bacterial strains of Streptococcus iniae. The cytotoxicity assay results showed that 27 strains (10.07%) exhibited cytotoxic activity against HeLa and A549 cell lines. Many actinobacterial strains with cytotoxic activity were identified as rare Actinobacteria, which illustrated that volcanic islands are vast reservoirs for Actinobacteria with promising antibacterial and cytotoxic activity. This study may significantly improve our understanding of actinobacterial communities on volcanic islands. The isolated Actinobacteria showed promising prospects for future use. [ABSTRACT FROM AUTHOR]

Many prokaryotes are covered by a two-dimensional array of proteinaceous subunits. This surface layers (S-layer) is incompletely characterized for many microorganisms. Here, we studied Bacillus cereus AH187. A genome analysis identified two genes encoding the S-layer proteins SL2 and EA1, which we experimentally confirmed to encode the two protein components of the S-layer covering the surface of B. cereus. Shotgun proteomics analysis indicated that SL2 is the major component of the B. cereus S-layer at the beginning of exponential growth, whereas EA1 becomes more abundant than SL2 during later stages of stationary growth. Microscopy analysis revealed the spatial organization of SL2 and EA1 at the surface of B. cereus to depend on their temporal-dynamics during growth. Our results also show that a mutant strain lacking functional SL2 and EA1 proteins has distinct surface properties compared to its parental strain, in terms of stiffness and hydrophilicity during the stationary growth phase. Surface properties, self-aggregation capacity, and bacterial adhesion were observed to correlate. We conclude that the dynamics of SL2 and EA1 expression is a key determinant of the surface properties of B. cereus AH187, and that the S-layer could contribute to B. cereus survival in starvation conditions. [ABSTRACT FROM AUTHOR]

Antimicrobial-resistant (AMR) foodborne bacteria causing bacterial infections pose a serious threat to human health. In addition, the ability of some of these bacteria to form biofilms increases the threat level as treatment options may become compromised. The extent of antibiotic resistance and biofilm formation among foodborne pathogens remain uncertain globally due to the lack of systematic reviews. We performed a meta-analysis on the global prevalence of foodborne pathogens exhibiting antibiotic resistance and biofilm formation using the methodology of a Cochrane review by accessing data from the China National Knowledge Infrastructure (CNKI), PubMed, and Web of Science databases between 2010 and 2020. A random effects model of dichotomous variables consisting of antibiotic class, sample source, and foodborne pathogens was completed using data from 332 studies in 36 countries. The results indicated AMR foodborne pathogens has become a worrisome global issue. The prevalence of AMR foodborne pathogens in food samples was greater than 10% and these foodborne pathogens were most resistant to β-lactamase antibiotics with Bacillus cereus being most resistant (94%). The prevalence of AMR foodborne pathogens in human clinical specimens was greater than 19%, and the resistance of these pathogens to the antibiotic class used in this research was high. Independently, the overall biofilm formation rate of foodborne pathogenic bacteria was 90% (95% CI, 68%–96%) and a direct linear relationship between biofilm formation ability and antibiotic resistance was not established. Future investigations should document both AMR and biofilm formation of the foodborne pathogen isolated in samples. The additional information could lead to alternative strategies to reduce the burden cause by AMR foodborne pathogens. [ABSTRACT FROM AUTHOR]

Bacillus cereus , an important foodborne pathogen, poses a risk to food safety and quality. Robust biofilm formation ability is one of the key properties that is responsible for the food contamination and food poisoning caused by B. cereus , especially the emetic strains. To investigate the mechanism of biofilm formation in emetic B. cereus strains, we screened for the mutants that fail to form biofilms by using random mutagenesis toward B. cereus 892-1, an emetic strain with strong biofilm formation ability. When knocking out flgE , a flagellar hook encoding gene, the mutant showed disappearance of flagellar structure and swimming ability. Further analysis revealed that both pellicle and ring presented defects in the null mutant compared with the wild-type and complementary strains. Compared with the flagellar paralytic strains Δ motA and Δ motB , the inhibition of biofilm formation by Δ flgE is not only caused by the inhibition of motility. Interestingly, Δ flgE also decreased the synthesis of cereulide. To our knowledge, this is the first report showing that a flagellar component can both affect the biofilm formation and cereulide production in emetic B. cereus , which can be used as the target to control the biohazard of emetic B. cereus. [ABSTRACT FROM AUTHOR]

The closely related members of the Bacillus cereus -group can mainly only be differentiated by whole genome sequencing. Among them, there are potentially toxin-producing bacteria. When consumed with food, these can cause vomiting or diarrhea and abdominal cramps. To date, although no EU-wide threshold exists, a bacterial count of 105 CFU/g can be regarded as critical. Specific and rapid detection of the bacteria is difficult due to their close relationship, and no loop-mediated isothermal amplification (LAMP) assay has been developed so far to detect potentially toxin-producing members of the B. cereus -group. Aim of this study was to develop a LAMP method to detect critical cell counts specifically and rapidly of potentially non-haemolytic enterotoxin (NHE)-producing cells of this group. A two-step LAMP assay was developed. First, the target sequence groEL was used to determine the representatives of the B. cereus -group. Second, since bacteria in which nheB is present are basically capable of producing enterotoxins, this gene was chosen for detection. The specificity of the developed assay was 100% for B. cereus -group isolates and 93.7% for the detection of nheB. The analytical sensitivity was 0.1 pg DNA/μl. Using simplified DNA extraction by boiling, cell-based sensitivity was determined. Targeting groEL and nheB , 11.35–27.05 CFU/reaction and 11.35–270.5 CFU/reaction were detectable, respectively. Artificially contaminated samples were investigated to prove the application in foods. Direct detection of the critical value of B. cereus -group cells was possible in 83.3% of samples and detecting the toxin-gene 50% thereof. After a 6-h incubation period, the detection rate increased to 100 and 91.7%, respectively. Additionally, 100 natively contaminated food samples were tested, also quantitatively and culturally. Samples with relevant contamination levels were reliably detected using groEL -LAMP. After a 6-h incubation period, isolates bearing the toxin gene nheB could also be reliably detected. In addition, colony material was boiled and used as a LAMP template for simple detection. Specificity for the B. cereus -group was 100 and 93.22% detecting nheB. The study demonstrated that screening of food samples with the groEL / nheB -LAMP assay can be performed within 1 day, making it possible to detect critical levels of potentially NHE-toxin-producing cells of the B. cereus -group. [ABSTRACT FROM AUTHOR]

Lettuce wraps are popular in Korean cuisine for their high nutritional value and versatility as healthy additions to multiple dishes. Microbial contamination of lettuce is a major concern, as lettuce is consumed fresh without cooking. Among foodborne pathogens, the spore-forming, facultative anaerobic bacterium, Bacillus cereus is one of the frequently detected pathogen in lettuce in Korea. In this study, we investigated the prevalence and distribution of Bacillus cereus strains in lettuce production farms and further evaluated the enterotoxin gene profiles, antibiotic susceptibility, multidrug resistance pattern, and genetic differences among the B. cereus group isolates. Of the 140 samples isolated from 10 lettuce production farms, 30 samples (21.42%) were positive for B. cereus in which 19 (31.6%) and 10 (23.25%) were from soil and lettuce, respectively. The enterotoxin patterns A (hblCDA, nheABC, entFM, and cytK genes) and B (hblCDA, nheABC, and entFM genes) accounted for 50% and 20% of all the isolates, whereas the emetic gene cesB was not detected in any of the B. cereus group isolates. Antibiotic susceptibility testing of the B. cereus group isolates revealed that all the strains were predominantly resistant to β-lactam antibiotics except imipenem and generally susceptible to most of the non β-lactam antibiotics, including gentamycin, streptomycin, chloramphenicol, and tetracycline. ERIC-PCR and MLST analysis revealed high genetic diversity among the 30 B. cereus group isolates, which belonged to 26 different sequence types (STs) and seven new STs. Moreover, isolates with identical STs exhibited similar patterns of antibiotic resistance and enterotoxin profiles. Results of this study indicate a high prevalence of B. cereus group isolates in lettuce production farms in the Republic of Korea.

The closely related members of the Bacillus cereus-group can mainly only be differentiated by whole genome sequencing. Among them, there are potentially toxin-producing bacteria. When consumed with food, these can cause vomiting or diarrhea and abdominal cramps. To date, although no EU-wide threshold exists, a bacterial count of 105 CFU/g can be regarded as critical. Specific and rapid detection of the bacteria is difficult due to their close relationship, and no loop-mediated isothermal amplification (LAMP) assay has been developed so far to detect potentially toxin-producing members of the B. cereus-group. Aim of this study was to develop a LAMP method to detect critical cell counts specifically and rapidly of potentially non-haemolytic enterotoxin (NHE)-producing cells of this group. A two-step LAMP assay was developed. First, the target sequence groEL was used to determine the representatives of the B. cereus-group. Second, since bacteria in which nheB is present are basically capable of producing enterotoxins, this gene was chosen for detection. The specificity of the developed assay was 100% for B. cereus-group isolates and 93.7% for the detection of nheB. The analytical sensitivity was 0.1 pg DNA/μl. Using simplified DNA extraction by boiling, cell-based sensitivity was determined. Targeting groEL and nheB, 11.35–27.05 CFU/reaction and 11.35–270.5 CFU/reaction were detectable, respectively. Artificially contaminated samples were investigated to prove the application in foods. Direct detection of the critical value of B. cereus-group cells was possible in 83.3% of samples and detecting the toxin-gene 50% thereof. After a 6-h incubation period, the detection rate increased to 100 and 91.7%, respectively. Additionally, 100 natively contaminated food samples were tested, also quantitatively and culturally. Samples with relevant contamination levels were reliably detected using groEL-LAMP. After a 6-h incubation period, isolates bearing the toxin gene nheB could also be reliably detected. In addition, colony material was boiled and used as a LAMP template for simple detection. Specificity for the B. cereus-group was 100 and 93.22% detecting nheB. The study demonstrated that screening of food samples with the groEL/nheB-LAMP assay can be performed within 1 day, making it possible to detect critical levels of potentially NHE-toxin-producing cells of the B. cereus-group.

Bacillus cereus, an important foodborne pathogen, poses a risk to food safety and quality. Robust biofilm formation ability is one of the key properties that is responsible for the food contamination and food poisoning caused by B. cereus, especially the emetic strains. To investigate the mechanism of biofilm formation in emetic B. cereus strains, we screened for the mutants that fail to form biofilms by using random mutagenesis toward B. cereus 892-1, an emetic strain with strong biofilm formation ability. When knocking out flgE, a flagellar hook encoding gene, the mutant showed disappearance of flagellar structure and swimming ability. Further analysis revealed that both pellicle and ring presented defects in the null mutant compared with the wild-type and complementary strains. Compared with the flagellar paralytic strains ΔmotA and ΔmotB, the inhibition of biofilm formation by ΔflgE is not only caused by the inhibition of motility. Interestingly, ΔflgE also decreased the synthesis of cereulide. To our knowledge, this is the first report showing that a flagellar component can both affect the biofilm formation and cereulide production in emetic B. cereus, which can be used as the target to control the biohazard of emetic B. cereus.

Many prokaryotes are covered by a two-dimensional array of proteinaceous subunits. This surface layers (S-layer) is incompletely characterized for many microorganisms. Here, we studied Bacillus cereus AH187. A genome analysis identified two genes encoding the S-layer proteins SL2 and EA1, which we experimentally confirmed to encode the two protein components of the S-layer covering the surface of B. cereus. Shotgun proteomics analysis indicated that SL2 is the major component of the B. cereus S-layer at the beginning of exponential growth, whereas EA1 becomes more abundant than SL2 during later stages of stationary growth. Microscopy analysis revealed the spatial organization of SL2 and EA1 at the surface of B. cereus to depend on their temporal-dynamics during growth. Our results also show that a mutant strain lacking functional SL2 and EA1 proteins has distinct surface properties compared to its parental strain, in terms of stiffness and hydrophilicity during the stationary growth phase. Surface properties, self-aggregation capacity, and bacterial adhesion were observed to correlate. We conclude that the dynamics of SL2 and EA1 expression is a key determinant of the surface properties of B. cereus AH187, and that the S-layer could contribute to B. cereus survival in starvation conditions.

In the natural environment, most microorganisms live in mixed-species biofilms, in which the metabolism and growth of organisms are different from that in single-species biofilms. Adhesive bacteria and their biofilms on the surface of food processing equipment are the sources of cross-contamination, leading to the risk for humans. Slightly acidic electrolyzed water (SAEW) has been proposed as a novel sanitizer in the food and agriculture industry. In this study, we investigated the changes in the physical properties of SAEW under different conditions and the disinfection abilities of SAEW against spore-forming and non-spore-forming pathogens. Furthermore, we examined the disinfection abilities of SAEW after 12 months of shelf life on a mixed-species biofilm of Listeria monocytogenes Scott A and Staphylococcus aureus. The results showed that SAEW at 30 and 50 ppm achieved all-kill of the spore-forming pathogen Bacillus cereus within 30 s. Changes in the ACC and pH of the produced SAEW were generally affected by the storage conditions. Both spore-forming and non-spore-forming pathogens were not detected under treatment with 50 ppm SAEW for 5 min under HDPE-closed conditions throughout the whole storage period. Moreover, 25 mg/L SAEW can inactivate L. monocytogenes Scott A and S. aureus biofilm cells in ~2.45 and 2.57 log CFU/mL in biofilms within 5-min treatment. However, the decline of the two bacteria in the mixed-species biofilm was 1.95 and 1.43 log CFU/mL, respectively. The changes in the cell membrane permeability of the mixed-species biofilm under treatment with SAEW were observed by using atomic force microscopy and confocal laser scanning microscopy. L. monocytogenes Scott A was more sensitive to SAEW in the mixed-species biofilm cells. These findings exhibited strong antibiofilm activities of SAEW in impairing biofilm cell membranes, decreasing cell density, and eliminating biofilm, which suggest that SAEW is an excellent antibacterial agent in the food processing industries. [ABSTRACT FROM AUTHOR]

Heavy metal resistant bacteria play an important role in the metal biogeochemical cycle in soil, but the benefits of microbial oxidation for plants and soil have not been well-documented. The purpose of this study was to explore the contribution of two Bacillus spp. to alleviate the antimony (Sb) toxicity in plants, and, then, to propose a bioremediation method for Sb contaminated soil, which is characterized by environmental protection, high efficiency, and low cost. This study explored the effects of Bacillus cereus HM5 and Bacillus thuringiensis HM7 inoculation on Broussonetia papyrifera and soil were evaluated under controlled Sb stressed conditions (0 and 100 mmol/L, antimony slag) through a pot experiment. The results show that the total root length, root volume, tips, forks, crossings, and root activities of B. papyrifera with inoculation are higher than those of the control group, and the strains promote the plant absorption of Sb from the soil environment. Especially in the antimony slag treatment group, B. cereus HM5 had the most significant effect on root promotion and promoting the absorption of Sb by B. papyrifera. Compared with the control group, the total root length, root volume, tips, forks, crossings, and root activities increased by 64.54, 70.06, 70.04, 78.15, 97.73, and 12.95%, respectively. The absorption of Sb by root, stem, and leaf increased by 265.12, 250.00, and 211.54%, compared with the control group, respectively. Besides, both B. cereus HM5 and B. thuringiensis HM7 reduce the content of malondialdehyde, proline, and soluble sugars in plant leaves, keeping the antioxidant enzyme activity of B. papyrifera at a low level, and alleviating lipid peroxidation. Principal component analysis (PCA) shows that both B. cereus HM5 and B. thuringiensis HM7 are beneficial to the maintenance of plant root functions and the improvement of the soil environment, thereby alleviating the toxicity of Sb. Therefore, B. cereus HM5 and B. thuringiensis HM7 in phytoremediation with B. papyrifera is a promising inoculant used for bacteria-assisted phytoremediation on Sb contaminated sites. [ABSTRACT FROM AUTHOR]