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Erwinia pyrifoliae, the Gram-negative bacterial pathogen responsible for black shoot blight, exhibits symptoms similar to E. amylovora (fire blight), though with distinct molecular characteristics. Given its prevalence primarily in South Korea and the availability of only nine assembled genomes, there is a lack of high-quality genome sequences and annotated genetic information for E. pyrifoliae. We present the sequencing and assembly of a Korean E. pyrifoliae strain, YKB12327, isolated from a diseased apple tree branch, using a combination of long Oxford Nanopore Technologies and short Illumina sequence reads. This genome comprises a circular chromosome and three plasmid sequences, totaling 4,061,634 bp. Annotation of YKB12327 identifies 3123 coding sequence protein-coding genes, 22 rRNA genes (5S, 16S, and 23S), and 76 tRNA genes. Our sequence data will enrich the current E. pyrifoliae genome resources and facilitate in understanding its evolution, diversity and structural variations, as well as the molecular basis of pathogenesis. [ABSTRACT FROM AUTHOR]

Biofilms are major virulence factors formed by pathogenic bacteria to invade their host and maintain their colony. While biofilms usually develop on diverse solid surfaces, floating biofilms, also called pellicles, are formed at the air–liquid interface. To address the problem of biofilm formation by bacterial pathogens, honey has been extensively studied. However, information on the effect of honey on biofilm formation by plant pathogens is scarce. This study aimed to determine the effects of manuka honey on biofilm and pellicle formation by Pectobacterium brasiliense and analyze the expression of genes encoding proteins needed to form biofilm by using semiquantitative PCR and RT‐qPCR. Treatment with 5% (w/v) of manuka honey significantly decreased biofilm and pellicle formation by P. brasiliense. RT‐qPCR results showed that the expression of bcsA, fis, hrpL, and expI decreased 7.07‐fold, 5.71‐fold, 13.11‐fold, and 6.26‐fold, respectively, after exposure to 5% (w/v) manuka honey. Our findings reveal that manuka honey may effectively inhibit biofilm and pellicle formation. [ABSTRACT FROM AUTHOR]

Erwinia amylovora, the causative agent of fire blight, causes significant economic losses for farmers worldwide by inflicting severe damage to the production and quality of plants in the Rosaceae family. Historically, fire blight control has primarily relied on the application of copper compounds and antibiotics, such as streptomycin. However, the emergence of antibiotic-resistant strains and growing environmental concerns have highlighted the need for alternative control methods. Recently, there has been a growing interest in adopting bacteriophages (phages) as a biological control strategy. Phages have demonstrated efficacy against the bacterial plant pathogen E. amylovora, including strains that have developed antibiotic resistance. The advantages of phage therapy includes its minimal impact on microbial community equilibrium, the lack of a detrimental impact on plants and beneficial microorganisms, and its capacity to eradicate drug-resistant bacteria. This review addresses recent advances in the isolation and characterization of E. amylovora phages, including their morphology, host range, lysis exertion, genomic characterization, and lysis mechanisms. Furthermore, this review evaluates the environmental tolerance of E. amylovora phages. Despite their potential, E. amylovora phages face certain challenges in practical applications, including stability issues and the risk of lysogenic conversion. This comprehensive review examines the latest developments in the application of phages for controlling fire blight and highlights the potential of E. amylovora phages in plant protection strategies. [ABSTRACT FROM AUTHOR]

Flowers serve as hubs for biotic interactions with pollinators and microbes, which can significantly impact plant reproduction and health. Previous studies have shown that the flower microbiota undergoes dynamic assembly processes during anthesis. However, the influence of foraging pollinators on the assembly and dispersal of the flower microbiota and the transmission of plant pathogens remains poorly understood. In this study, we used insect exclusion netting to investigate the role of pollinators in the assembly of the microbiota on apple stigma and the transmission of the fire blight pathogen Erwinia amylovora. We found that excluding pollinators had a minor impact on the community diversity and composition of the apple stigma microbiota, while the flower's developmental stage had a strong influence. Additionally, pollinator exclusion altered bacterial dispersal and the relative abundance of different bacterial species, including E. amylovora, suggesting that pollinators play a role in transmitting plant pathogens. Using a reporter system, we demonstrated that bumble bees can transmit the fire blight pathogen from an infected flower under controlled growth conditions. Our study highlights the importance of intrinsic and pollinator‐independent microbes as sources of inoculum for the stigma microbiota and underscores the role of foraging pollinators in vectoring plant pathogens. [ABSTRACT FROM AUTHOR]

Erwinia amylovora bacteriophages are of interest as fire blight control agents. This paper presents data on the biology and molecular genetic properties of 12 E. amylovora tailed bacteriophages. Genome sequences of seven of them were determined and the phages were identified as the representatives of Caudoviricetes; Vequintavirinae, Ounavirinae and Autographiviridae families. The bacteriophages studied were active against E. amylovora, Pantoea agglomerans and Pantoea ananatis strains. The myovirus Hena1 had the narrowest host range lysing 12% of the bacterial cultures tested, the remaining myoviruses—had broader host ranges (56%) for this collection. The phages showed different reactions to the presence of a chelating agent in the cultivation medium. A significant proportion of phage-resistant E. amylovora cells were found both in infected liquid cultures and in the experiments on the plates with the phage agar (more than 20% in case of exposure to podoviruses), which correlates with the data of limited number of previous investigations of the phenomenon for E. amylovora interactions with phages. High prevalence of resistant cells in the host cultures suggest that they are formed not due to spontaneous mutations but result from another phenotypic or genetic dissociation mechanism(s) that remains to be identified. [ABSTRACT FROM AUTHOR]

Pectocin M1 (PM1), the bacteriocin from phytopathogenic Pectobacterium carotovorum which causes soft rot disease, has a unique ferredoxin domain that allows it to use FusA of the plant ferredoxin uptake system. To probe the structure‐based mechanism of PM1 uptake, we determined the X‐ray structure of full‐length PM1, containing an N‐terminal ferredoxin and C‐terminal catalytic domain connected by helical linker, at 2.04 Å resolution. Based on published FusA structure and NMR data for PM1 ferredoxin domain titrated with FusA, we modeled docking of the ferredoxin domain with FusA. Combining the docking models with the X‐ray structures of PM1 and FusA enables us to propose the mechanism by which PM1 undergoes dynamic domain rearrangement to translocate across the target cell outer membrane. [ABSTRACT FROM AUTHOR]

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Pectobacterium carotovorum and Pectobacterium aroidearum represent the primary pathogens causing variable soft rot disease. However, the fundamental defense responses of Pinellia ternata to pathogens remain unclear. Our investigation demonstrated that the disease produced by P. carotovorum is more serious than P. aroidearum. RNA-seq analysis indicated that many cell wall-related genes, receptor-like kinase genes, and resistance-related genes were induced by P. aroidearum and P. carotovorum similarly. But many different regulatory pathways exert a crucial function in plant immunity against P. aroidearum and P. carotovorum, including hormone signaling, whereas more auxin-responsive genes were responsive to P. carotovorum, while more ethylene and gibberellin-responsive genes were responsive to P. aroidearum. 12 GDSL esterase/lipase genes and 3 fasciclin-like arabinogalactan protein genes were specifically upregulated by P. carotovorum, whereas 11 receptor-like kinase genes and 8 disease resistance genes were up-regulated only by P. aroidearum. Among them, a lectin gene (part1transcript/39001) was induced by P. carotovorum and P. aroidearum simultaneously. Transient expression in N. benthamiana demonstrated that the lectin gene improves plant resistance to P. carotovorum. This study offers a comprehensive perspective on P. ternata immunity produced by different soft rot pathogens and reveals the importance of lectin in anti-soft rot of P. ternata for the first time. [ABSTRACT FROM AUTHOR]

Previous studies revealed that the type VI secretion system (T6SS) has an essential role in bacterial competition and virulence in many gram-negative bacteria. However, the role of T6SS in virulence in Pectobacterium atrosepticum remains controversial. We examined a closely related strain, PccS1, and discovered that its T6SS comprises a single-copy cluster of 17 core genes with a higher identity to homologs from P. atrosepticum. Through extensive phenotypic and functional analyses of over 220 derivatives of PccS1, we found that three of the five VgrGs could be classified into group I VgrGs. These VgrGs interacted with corresponding DUF4123 domain proteins, which were secreted outside of the membrane and were dependent on either the T6SS or type IV secretion system (T4SS). This interaction directly governed virulence and competition. Meanwhile, supernatant proteomic analyses with strains defective in the T6SS and/or T4SS confirmed that effectors, such as FhaB, were secreted redundantly to control the virulence and suppress host callose deposition in the course of infection. Notably, this redundant secretion mechanism between the T6SS and T4SS is believed to be the first of its kind in bacteria. [ABSTRACT FROM AUTHOR]

Objective: To introduce the Cre-loxP system for constructing marker-less multiple-gene deletion mutants in Pectobacterium, overcoming limitations of antibiotic markers and enhancing the understanding of pathogenic mechanisms. Results: Firstly, a plasmid named pEX18-Cre, containing a sacB sucrose suicide gene, was constructed to express Cre recombinase in Pectobacterium. Secondly, a mutant in which the loxP-Km fragment replaced the target gene was obtained through homologous recombination double-crossover with the chromosome. Finally, pEX18-Cre was introduced into the mutant to excise the DNA between the loxP sites, thereby removing the markers and achieving multiple gene deletions. By utilizing the Cre-loxP system, we successfully constructed multiple marker-less gene deletion mutants in Pectobacterium strains. Conclusions: The Cre-loxP system efficiently creates marker-less multiple-gene deletion mutants, enhancing the study of Pectobacterium pathogenic mechanisms by overcoming antibiotic marker limitations. [ABSTRACT FROM AUTHOR]

In Algeria, potatoes ranks second among the twenty main food crops. It's characterized by periods of overproduction corresponding to seasonal crops. Except these periods, supply tends to fall. In order for the availability of potatoes to be constant throughout the non-harvest periods, it is imperative to store the surplus production to ensure a constant supply during periods of unavailability of a new harvest. The storage of the potato must maintain a satisfactory quality and minimize losses and the postharvest development of bacteria and fungi. This work aims to identify and follow the evolution of pectinolytic Erwinia and Erwinia soft rot during storage at 4 and 10° C of two varieties of potato grown in Algeria, i.e. Spunta and Désirée. The results indicated the presence of three species of Erwinia: E. carotovora subsp. carotovora, E. carotovora subsp. atroseptica and E. chrysanthemi. Initially, for both varieties, E. carotovora subsp. carotovora predominates followed by E. carotovora subsp. atroseptica and finally E. chrysanthemi. During storage, the three species evolve almost in the same way and their multiplication is more important at 10° C than at 4° C, particularly on the Spunta. About the total bacteria, the highest levels are recorded on Spunta, especially at 10° C. In addition, the Erwinia spp. / total bacteria ratio showed that Erwinia spp. are very most abundant compared to the total bacteria. The assessment of soft rot losses has also shown that they are greater in the Spunta variety whether at 4 or 10° C. [ABSTRACT FROM AUTHOR]

Phytopathogenic bacteria of the genus Pectobacterium are responsible for several diseases that affect potato (Solanum tuberosum L.) production worldwide, including blackleg and tuber soft rot. These bacteria are highly diverse, with over 17 different species currently identified. However, some of the recently described species, such as Pectobacterium punjabense, are still poorly understood. In this study, we focused on P. punjabense isolates collected from diseased potato tubers in Russia in 2021. Whole-genome sequencing was used to characterise the genomic diversity of the pathogen and determine the biochemical profiles of the isolated bacteria. The ability of these isolates to cause soft rot symptoms was tested. A comparative assessment of the potential pathogenicity of the Pectobacterium isolates was conducted by infecting potato tubers and measuring the accumulation of biomass in a liquid medium during cultivation at different temperatures. A TaqMan qPCR assay was developed for the highly sensitive and specific characterisation of P. punjabense strains, which can be used in diagnostic systems. This is the first report on P. punjabense causing potato disease in the Russian Federation. [ABSTRACT FROM AUTHOR]

Fire blight, caused by Erwinia amylovora, can be spread through orchards and nurseries because of poor sanitation practices such as contaminated secateurs. This research investigated the efficacy of 12 commercial sterilants at varying concentrations to kill E. amylovora on secateurs. Secateurs were dipped into an Erwinia amylovora inoculum solution (106 colony forming units/mL), and then misted with a test sterilant. After 10 s, secateurs were swabbed and plated onto Kings B agar plate, incubated at 26 °C for 48 h and bacterial colonies counted. Sterilants were also assessed for cotton bleaching and metal corrosion. Best performing sterilants were then tested as described above by cutting through infected plant material containing sticky bacterial ooze as inoculum. Each of the sterilants tested (methylated spirits (95% and 70%), sodium hypochlorite (NaOCl) (1%, 0.5%, 0.135%), Bac-Stop/benzalkonium chloride (2%, 1%), Virkon™ (label rate), Dettol (50%, 10%, 1%, 0.1%), and HarvestCide® gel (0.1%, 0.5%, 1%)) were found to be effective to kill E. amylovora on inoculum-coated secateurs. The best performing sterilants (methylated spirits, Dettol, HarvestCide gel, NaOCl) were also effective in killing E. amylovora on infected plant material when compared with the untreated control. Most sterilants, except methylated spirits or Dettol, caused corrosion of metal and bleaching of cotton. Each of the tested sterilants were found to be effective to kill Erwinia amylovora on inoculum-coated secateurs and inoculum in plant material and bacterial ooze. Many of the best performing sterilants were likely to damage tools over time and cause bleaching on clothing. However, Dettol or methylated spirits did not cause metal corrosion or bleaching. [ABSTRACT FROM AUTHOR]

Fire blight caused by bacterium Erwinia amylovora is one of the most damaging diseases of apple and pear trees and many other plant species of the Rosaceae family. So far, it has been detected in almost all areas of pome fruit cultivation and in some regions it causes economic damage every year. Plant protection against fire blight is aimed at both preventing their infection and controlling the disease. However, the protection of plants against bacteriosis is generally difficult due to the small range of plant protection products and the growing doubts about their safety for the environment. Limitations related to their use have resulted in an increased interest in alternative methods, including the method of biological protection using various microorganisms. The first research on biological control agents was conducted in the USA about 100 years ago. Currently, it is also carried out in other countries, especially where fire blight causes economic losses. Commercial products whose active ingredients are mainly bacteria have already been developed. This work is a review of the studies and achievements in this field from its beginnings focusing on the Gram-negative bacteria and bacteriophages as a biocontrol agents. [ABSTRACT FROM AUTHOR]

The genus Erwinia includes plant-pathogenic, non-pathogenic and even opportunistic human pathogens. Among them, Erwinia amylovora is one of the most studied species, as the etiological agent of the relevant necrotic plant disease fire blight. Its most important pathogenicity factor is amylovoran, an exopolysaccharide essential in the formation of a protective biofilm used by the bacterium to escape the plant protection mechanisms. Amylovoran biosynthesis, regulation and secretion require the concerted action of twelve genes clustered in a region spanning 16 kb, the ams operon. Most of the encoded proteins build and polymerize the repeating oligosaccharide units of galactose, glucose, glucuronic acid and pyruvate, others have signalling, regulation and secretion functions. We compared the ams operon organisation, predicted 3D structure of the encoded proteins of Erwinia amylovora in eighteen Erwinia species. We detected the presence of a paralog (for the amsG gene) and some rearrangements in the EPS biosynthetic operon in specific taxa that could be connected to the species-specific pathogenicity profile. The present study adds fundamental information about the genomic determinants of exopolysaccharide secretion in the Erwinia genus, and clarifies the evolutionary relationships among the genes in the ams operon. [ABSTRACT FROM AUTHOR]

Bacteriophages offer unique benefits for the specific control of Erwinia amylovora, the causative agent of fire blight in pome fruit. Unfortunately, the majority of described phages were tested for efficacy in vitro only. Data from infection assays using pear slices or detached blossoms is rare and field trials are barely reported. It remains to be studied if bacteriophages could control fire blight in the open field. This review summarizes current knowledge of different phages infecting E. amylovora. In addition, the requirements for a phage to optimally function as a biological antimicrobial agent in agriculture are discussed together with the ideal setup of field trials and the formulation of phages for best results. [ABSTRACT FROM AUTHOR]

BACKGROUND: Canonical biocontrol bacteria were considered to inhibit pathogenic bacteria mainly by secreting antibiotic metabolites or enzymes. Recent studies revealed that some biocontrol bacteria can inhibit pathogenic bacteria through contact‐dependent killing (CDK) mediated by contact‐dependent secretion systems. The CDK was independent of antibiotic metabolites and often ignored in normal biocontrol activity assay. RESULTS: In this study, we aimed to use a pathogen enrichment strategy to isolate non‐canonical bacteria with CDK ability. Rhizosphere soil samples from Chinese cabbage showing soft rot symptom were collected and Pectobacterium carotovorum subsp. carotovorum (Pcc), the pathogen of cabbage soft rot, were added into these samples to enrich bacteria which attached on Pcc cells. By co‐culture with Pcc, four bacteria strains (named as PcE1, PcE8, PcE12 and PcE13) showing antibacterial activity were isolated from Chinese cabbage rhizosphere. These four bacteria strains showed CDK abilities to different pathogenic bacteria of horticultural plants. Among them, PcE1 was identified as Chryseobacterium cucumeris. Genome sequencing showed that PcE1 genome encoded a type VI secretion system (T6SS) gene cluster. By heterologous expression, four predicted T6SS effectors of PcE1 showed antibacterial activity to Escherichia coli. CONCLUSION: Overall, this study isolated four bacteria strains with CDK activity to various horticultural plant pathogens, and revealed possible involvement of T6SS of Chryseobacterium cucumeris in antibacterial activity. These results provide valuable insight for potential application of CDK activity in biocontrol bacteria. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Bacterial soft rot caused by coinfection with Dickeya spp. and Pectobacterium spp. in hosts can cause successive changes in fields, and it is difficult to prevent the spread of and control the infection. Pectobacterium spp. are prevalent in the growing areas of tuberous crops, including taro and potato. Recently, Dickeya fangzhongdai has emerged as a virulent pathogen in taro. To determine the prevalence status of the causal agents and evaluate the potential spreading risks of D. fangzhongdai, screening and taxonomic classification were performed on phytopathogenic bacteria collected from different taro-growing areas in Guangdong Province, China, and biological and genomic characteristics were further compared among typical strains from all defined species. The causative agents were verified to be phytobacterial strains of D. fangzhongdai, Pectobacterium aroidearum and Pectobacterium colocasium. P. aroidearum and P. colocasium were found to form a complex preferring Araceae plants and show intensive genomic differentiation, indicating their ancestor had adapted to taro a long time prior. Compared with Pectobacterium spp., D. fangzhongdai was more virulent to taro corms under conditions of exogenous infection and more adaptable at elevated temperatures. D. fangzhongdai strains isolated from taro possessed genomic components of additional T4SSs, which were accompanied by additional copies of the hcp-vgrG genes of the T6SS, and these contributed to the expansion of their genomes. More gene clusters encoding secondary metabolites were found within the D. fangzhongdai strains than within the Pectobacterium complex; interestingly, distinct gene clusters encoding zeamine and arylpolyene were both most similar to those in D. solani that caused potato soft rot. These comparisons provided genomic evidences for that the newly emerging pathogen was potentially equipped to compete with other pathogens. Diagnostic qPCR verified that D. fangzhongdai was prevalent in most of the taro-growing areas and coexisted with the Pectobacterium complex, while the plants enriching D. fangzhongdai were frequently symptomatic at developing corms and adjacent pseudostems and caused severe symptoms. Thus, the emerging need for intensive monitoring on D. fangzhongdai to prevent it from spreading to other taro-growing areas and to other tuberous crops like potato; the adjustment of control strategies based on different pathopoiesis characteristics is recommended. [ABSTRACT FROM AUTHOR]

Bacterial soft rots are amongst the most economically important diseases that cause significant yield losses in various crops. A clear identification of the causal agents is required to develop management strategies. In 2022 and 2023, after the widespread occurrence of soft rot disease in sugar beet fields in the Firuzan region, Hamedan Province, Iran, the current study was conducted to identify and characterize the causal agents. A total of 38 bacterial isolates were obtained from sugar beet plants with soft rot symptoms and subjected to biochemical and phenotypical characterization and pathogenicity tests on healthy slices from potato tubers and sugar beet taproots. Twelve isolates from this study along with the type strain Pectobacterium carotovorum ICMP 5702 were selected for subsequent screening by BOX‐PCR. Six isolates were chosen for sequencing the 16SrRNA gene and phylogenetic analysis. In BLAST analyses, the pathogenic isolates S2, S9, S22, S11, S23 and 111 showed the highest similarity values (≥99%) with the reference sequences of Raoultella terrigena, Klebsiella michiganensis, Erwinia (Winslowiella) iniecta, Pantoea agglomerans and P. carotovorum, respectively. These isolates induced soft rot and maceration on plant materials from five species (bell pepper fruits, garlic cloves and slices from sugar beet taproot, potato tubers and carrot roots) 72 h after inoculation. In the greenhouse experiment, they caused soft rot symptoms in the taproots of 2‐month‐old sugar beet plants 3 weeks after inoculation. These soft rot agents had Gram‐negative, catalase‐positive and oxidase‐negative reactions, grew under both aerobic and anaerobic conditions, tolerated and grew at 37°C and 5% NaCl. In general, the results of this research showed that in addition to Pectobacterium, four other genera from the order Enterobacterales including Erwinia, Pantoea, Klebsiella and Raoultella, are amongst the causes of soft rot in sugar beet in Firuzan region of Hamedan. [ABSTRACT FROM AUTHOR]

BACKGROUND: The potential of copper nanoparticles (Cu‐NPs) to be used as an alternative control strategy against olive fruit flies (Bactrocera oleae) with reduced sensitivity to the pyrethroid deltamethrin and the impact of both nanosized and bulk copper hydroxide (Cu(OH)2) on the insect's reproductive and endosymbiotic parameters were investigated. RESULTS: The application of nanosized and bulk copper applied by feeding resulted in significant levels of adult mortality, comparable to or surpassing those achieved with deltamethrin at recommended doses. Combinations of Cu‐NPs or copper oxide nanoparticles (CuO‐NPs) with deltamethrin significantly enhanced the insecticide's efficacy against B. oleae adults. When combined with deltamethrin, Cu‐NPs significantly reduced the mean total number of offspring compared with the control, and the number of stings, pupae, female and total number of offspring compared with the insecticide alone. Both bulk and nanosized copper negatively affected the abundance of the endosymbiotic bacterium Candidatus Erwinia dacicola which is crucial for the survival of B. oleae larvae. CONCLUSION: The Cu‐NPs can aid the control of B. oleae both by reducing larval survival and by enhancing deltamethrin performance in terms of toxicity and reduced fecundity, providing an effective anti‐resistance tool and minimizing the environmental footprint of synthetic pesticides by reducing the required doses for the control of the pest. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Background: Pancreatic ductal adenocarcinoma (PDAC) is an aggressive disease without meaningful therapeutic options beyond the first salvage therapy. Targeting PDAC metabolism through amino acid restriction has emerged as a promising new strategy, with asparaginases, enzymes that deplete plasma glutamine and asparagine, reaching clinical trials. In this study, we investigated the anti-PDAC activity of the asparaginase formulation Pegcrisantaspase (PegC) alone and in combination with standard-of-care chemotherapeutics. Methods: Using mouse and human PDAC cell lines, we assessed the impact of PegC on cell proliferation, cell death, and cell cycle progression. We further characterized the in vitro effect of PegC on protein synthesis as well as the generation of reactive oxygen species and levels of glutathione, a major cellular antioxidant. Additional cell line studies examined the effect of the combination of PegC with standard-of-care chemotherapeutics. In vivo, the tolerability and efficacy of PegC, as well as the impact on plasma amino acid levels, was assessed using the C57BL/6-derived KPC syngeneic mouse model. Results: Here we report that PegC demonstrated potent anti-proliferative activity in a panel of human and murine PDAC cell lines. This decrease in proliferation was accompanied by inhibited protein synthesis and decreased levels of glutathione. In vivo, PegC was tolerable and effectively reduced plasma levels of glutamine and asparagine, leading to a statistically significant inhibition of tumor growth in a syngeneic mouse model of PDAC. There was no observable in vitro or in vivo benefit to combining PegC with standard-of-care chemotherapeutics, including oxaliplatin, irinotecan, 5-fluorouracil, paclitaxel, and gemcitabine. Notably, PegC treatment increased tumor expression of asparagine and serine biosynthetic enzymes. Conclusions: Taken together, our results demonstrate the potential therapeutic use of PegC in PDAC and highlight the importance of identifying candidates for combination regimens that could improve cytotoxicity and/or reduce the induction of resistance pathways. [ABSTRACT FROM AUTHOR]

Background: The reduced rate of potato production may occur under different conditions such as field, transit, storage, and marketing. Potato cultivation is frequently affected by various pathogens, among which Pectobacterium carotovorum subsp. carotovorum is a notorious bacterial pathogen responsible for causing bacterial soft rot disease. This pathogen poses a significant threat to potato production worldwide, resulting in substantial economic losses and food security concerns. This study aimed to investigate the effectiveness of three bacterial bioagents, namely Brevundimonas bullata, Bacillus siamensis, and Bacillus velezensis, against P. carotovorum subsp. carotovorum, a notorious bacterium responsible for causing potato tuber soft rot disease. Results: Fifteen isolates were isolated from rhizosphere of potato plants. Out of 15 isolates, 3 isolates, No. 1, 11, and 12, showed highly antagonistic property to control the growth of P. carotovorum subsp. carotovorum in vitro. They were identified as B. bullata, B. velezensis, and B. siamensis, by using 16S rRNA nucleotide sequence analysis. Results from these experiments revealed that three bioagents exhibited notable inhibitory effects on the growth of the pathogenic bacterium. However, B. velezensis stood out as the most effective inhibitor among the tested bioagents, showcasing the highest level of bacteriostatic activity (2.6 cm). The findings from the in vitro experiments provided promising insights into the potential of these bacterial bioagents as natural antagonists against potato tuber soft rot disease. Building upon these promising results, the study recommended the utilization of all tested bioagents for controlling soft rot disease in potato tubers, especially during storage conditions where the risk of bacterial proliferation is heightened. Treatment with B. bullata, B. siamensis, and B. velezensis demonstrates varying degrees of efficacy in controlling the progression of soft rot disease. Notably, B. velezensis shows promising results with relatively low disease severity scores across all time points compared to the other treatments. B. velezensis demonstrates the lowest disease severity percentage at 7.00% compared to the other treatments. Conclusions: The study underscores the significant potential of B. bullata, B. siamensis, and B. velezensis as effective biological control agents against potato tuber soft rot disease. By targeting the causative agent directly, these bioagents offer a promising avenue for mitigating the detrimental impact of soft rot disease on potato production, thereby contributing to improved crop yield and quality. [ABSTRACT FROM AUTHOR]

Bacteriophages have emerged as effective antimicrobial agents in combating pathogenic bacteria. To successfully apply phages in real‐life scenarios, it is crucial to optimize their large‐scale production, concentration and purification processes. In this study, our objective was to optimize the phage concentration parameters with a high recovery rate within a shorter time and minimum chemical consumption. We isolated and characterized a specific Erwinia amylovora phage. Subsequently, we employed response surface methodology (RSM) combined with a three‐factor central composite design to optimize the phage recovery. The factors considered were polyethylene glycol (PEG) concentration, NaCl concentration and incubation time. The optimized values for PEG, NaCl and incubation time, which resulted in a maximum recovery rate of 85.37%, were determined as 18%, 2.38 M and 0 h, respectively. This finding indicates that the concentration step, which traditionally took up to 18 h with a recovery rate of 65%, can now be accomplished in a significantly shorter time with an improved recovery rate. Our study demonstrates the effectiveness of RSM to identify the optimum conditions for phage precipitation. This approach allows for the rapid and efficient design of precipitation protocols tailored to specific bacteriophages, resulting in shorter processing times and higher recovery rates. [ABSTRACT FROM AUTHOR]

Some strains of nonpathogenic Allorhizobium vitis can control crown gall disease in grapevines caused by pathogenic A. vitis and are considered candidates for biocontrol agents. Many plant pathogenic bacteria regulate the expression of their virulence genes via quorum sensing using N -acylhomoserine lactone (AHL) as a signaling compound. The eight nonpathogenic A. vitis strains used in this study showed AHL-degrading activity. The complete genome sequence of A. vitis MAFF 212306 contained three AHL lactonase gene homologs. When these genes were cloned and transformed into Escherichia coli DH5α, E. coli harboring the aiiV gene (RvVAR031_27660) showed AHL-degrading activity. The aiiV coding region was successfully amplified by polymerase chain reaction from the genomes of all eight strains of nonpathogenic A. vitis. Purified His-tagged AiiV exhibited AHL lactonase activity by hydrolyzing the lactone ring of AHL. AiiV had an optimal temperature of approximately 30 °C; however, its thermostability decreased above 40 °C. When the AiiV-expressing plasmid was transformed into Pectobacterium carotovorum subsp. carotovorum NBRC 3830, AHL production by NBRC 3830 decreased below the detection limit, and its maceration activity, which was controlled by quorum sensing, almost disappeared. These results suggest the potential use of AHL-degrading nonpathogenic A. vitis for the inhibition of crown gall disease in grapevines and other plant diseases controlled by quorum sensing. [ABSTRACT FROM AUTHOR]

Potato (Solanum tuberosum L.) is considered one of the main food crops in many countries worldwide. The present work was planned to manage potato black-leg disease using organic treatments as well as mineralnitrogenous treatments, in addition to examining their effects on the pathogenic bacterium (Pectobacterium atrosepticum) population under artificial inoculation conditions. The obtained data indicated that applications of cabbage, onion and peppermint dry ground leaves as organic matters, and applications of ammonium super-phosphate, potassium sulfate and urea as mineral-nitrogenous fertilizers reduced P. atrosepticum population and black-leg disease of potato compared with the control treatment. In addition, these treatments led to increasing potato yield, while the beneficial effects increased with increasing their doses compared with the control treatment. Meanwhile, the organic matters appeared highly effective compared with mineral-nitrogenous fertilizers in disease reduction. However, mineral-nitrogenous fertilizers appeared highly effective in increasing potato yield. Meanwhile, onion dry ground leaves (organic matter) and urea (nitrogenous fertilizer) were the most effective on the pathogenic bacterium population and severity of the disease compared with other treatments. [ABSTRACT FROM AUTHOR]

We recently discovered that some bacteriophages establish a nucleus-like replication compartment (phage nucleus), but the core genes that define nucleus-based phage replication and their phylogenetic distribution were still to be determined. Here, we show that phages encoding the major phage nucleus protein chimallin share 72 conserved genes encoded within seven gene blocks. Of these, 21 core genes are unique to nucleus-forming phage, and all but one of these genes encode proteins of unknown function. We propose that these phages comprise a novel viral family we term Chimalliviridae. Fluorescence microscopy and cryoelectron tomography studies of Erwinia phage vB_EamM_RAY confirm that many of the key steps of nucleus-based replication are conserved among diverse chimalliviruses and reveal variations on this replication mechanism. This work expands our understanding of phage nucleus and PhuZ spindle diversity and function, providing a roadmap for identifying key mechanisms underlying nucleus-based phage replication.

Introduction: Pectobacterium betavasculorum is a member of the Pectobacerium genus that inhabits a variety of niches and is found in all climates. Bacteria from the Pectobacterium genus can cause soft rot disease on various plants due to the secretion of plant cell wall degrading enzymes (PCWDEs). The species P. betavasculorum is responsible for the vascular necrosis of sugar beet and soft rot of many vegetables. It also infects sunflowers and artichokes. The main sugar present in sugar beet is sucrose while xylose is one of the main sugars in artichoke and sunflower. Methods: In our work, we applied metabolomic studies coupled with genomics to investigate the metabolism of P. betavasculorum in the presence of xylose and sucrose as the only carbon source. The ability of the strains to use various sugars as the only carbon source were confirmed by the polypyridyl complex of Ru(II) method in 96-well plates. Results: Our studies provided information on the metabolic pathways active during the degradation of those substrates. It was observed that different metabolic pathways are upregulated in the presence of xylose in comparison to sucrose. Discussion: The presence of xylose enhances extracellular metabolism of sugars and glycerol as well as stimulates EPS and IPS synthesis. In contrast, in the presence of sucrose the intensive extracellular metabolism of amines and amino acids is promoted. [ABSTRACT FROM AUTHOR]

Potato soft rot caused by Pectobacterium spp. are devastating diseases of potato which cause severe economic losses worldwide. Pectobacterium brasiliense is considered as one of the most virulent species. However, the virulence mechanisms and pathogenicity factors of this strain have not been fully elucidated. Here, through pathogenicity screening, we identified two Pectobacterium brasiliense isolates, SM and DQ, with distinct pathogenicity levels. SM exhibits higher virulence compared to DQ in inducing aerial stem rot, blackleg and tuber soft rot. Our genomic and transcriptomic analyses revealed that SM encodes strain specific genes with regard to plant cell wall degradation and express higher level of genes associated with bacterial motility and secretion systems. Our plate assays verified higher pectinase, cellulase, and protease activities, as well as fast swimming and swarming motility in SM. Importantly, a unique endoglucanase S specific to SM was identified. Expression of this cellulase in DQ greatly enhances its virulence compared to wild type strain. Our study sheds light on possible determinants causing different pathogenicity of Pectobacterium brasiliense species with close evolutionary distance and provides new insight into the direction of genome evolution in response to host variation and environmental stimuli. [ABSTRACT FROM AUTHOR]

In 2022, a novel disease similar to pear fire blight was found in a pear orchard in Zhangye City, Gansu Province, China. The disease mainly damages the branches, leaves, and fruits of the plant. To identify the pathogen, tissue isolation and pathogenicity testing (inoculating the potential pathogen on healthy plant tissues) were conducted. Furthermore, a comprehensive analysis encompassing the pathogen's morphological, physiological, and biochemical characteristics and whole-genome sequencing was conducted. The results showed that among the eight isolates, the symptoms on the detached leaves and fruits inoculated with isolate DE2 were identical to those observed in the field. Verifying Koch's postulates confirmed that DE2 was the pathogenic bacterium that causes the disease. Based on a 16S rRNA phylogenetic tree, isolate DE2 belongs to the genus Erwinia. Biolog and API 20E results also indicated that isolate DE2 is an undescribed species of Erwinia. Isolate DE2 was negative for oxidase. Subsequently, the complete genome sequence of isolate DE2 was determined and compared to the complete genome sequences of 29 other Erwinia species based on digital DNA-DNA hybridization (dDDH) and average nucleotide identity (ANI) analyses. The ANI and dDDH values between strain DE2 and Erwinia species were both below the species thresholds (ANI < 95-96%, dDDH<70%), suggesting that isolate DE2 is a new species of Erwinia. We will temporarily name strain DE2 as Erwinia pyri sp. nov. There were 548 predicted virulence factors in the genome of strain DE2, comprising 534 on the chromosome and 5 in the plasmids. The whole genome sequence of strain DE2 has been submitted to the NCBI database (ASM3075845v1) with accession number GCA_030758455.1. The strain DE2 has been preserved at the China Center for Type Culture Collection (CCTCC) under the deposit number CCTCC AB 2024080. This study represents the initial report of a potentially new bacterial species in the genus Erwinia that causes a novel pear dieback disease. The findings provide a valuable strain resource for the study of the genus Erwinia and establish a robust theoretical foundation for the prevention and control of emerging pear dieback diseases. [ABSTRACT FROM AUTHOR]

Quorum sensing (QS) is a conserved cell-cell communication mechanism widely distributed in bacteria, and is oftentimes tightly correlated with pathogen virulence. Quorum quenching enzymes, which interfere with QS through degrading the QS signaling molecules, could attenuate virulence instead of killing the pathogens, and thus are less likely to induce drug resistance. Many Gram-negative bacteria produce N-acyl homoserine lactones (AHLs) for interspecies communication. In this study, we isolated and identified a bacterial strain, Mesoflavibacter zeaxanthinifaciens XY-85, from an Onchidium sp. collected from the intertidal zone of Dapeng Reserve in Shenzhen, China, and found it had strong AHL degradative activity. Whole genome sequencing and blast analysis revealed that XY-85 harbors an AHL lactonase (designated MzmL), which is predicted to have an N-terminal signal peptide and share the "HXHXDH" motif with known AHL lactonases belonging to the Metallo-ß-lactamase superfamily. Phylogenetic studies showed MzmL was closest to marine lactonase cluster members, MomL and Aii20J, instead of the AiiA type lactonases. Ultra performance liquid chromatography-mass spectrometry analysis confirmed that MzmL functions as an AHL lactonase catalyzing AHL degradation through lactone hydrolysis. MzmL could degrade both short- and long-chain AHLs with or without a substitution of oxo-group at the C-3 position, and retained full bioactivity under a wide range of temperatures (28-100°C) and pHs (4-11). Furthermore, MzmL significantly reduced Pectobacterium carotovorum subsp. carotovorum virulence factor production in vitro, such as biofilm formation and plant cell wall degrading enzyme production, and inhibited soft rot development on potato slices. These results demonstrated that MzmL may be a novel type of AHL lactonase with good environmental stability, and has great potential to be developed into a novel biological control agent for bacterial disease management. [ABSTRACT FROM AUTHOR]

According to an estimate, 30% to 40%, of global fruit are wasted, leading to post harvest losses and contributing to economic losses ranging from $10 to $100 billion worldwide. Among, all fruits the discarded portion of oranges is around 20%. A novel and value addition approach to utilize the orange peels is in nanoscience. In the present study, a synthesis approach was conducted to prepare the metallic nanoparticles (copper and silver); by utilizing food waste (Citrus plant peels) as bioactive reductants. In addition, the Citrus sinensis extracts showed the reducing activity against metallic salts copper chloride and silver nitrate to form Cu-NPs (copper nanoparticles) and Ag-NPs (Silver nanoparticles). The in vitro potential of both types of prepared nanoparticles was examined against plant pathogenic bacteria Erwinia carotovora (Pectobacterium carotovorum) and pathogens effect on human health Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Moreover, the in vivo antagonistic potential of both types of prepared nanoparticles was examined by their interaction with against plant (potato slices). Furthermore, additional antipathogenic (antiviral and antifungal) properties were also examined. The statistical analysis was done to explain the level of significance and antipathogenic effectiveness among synthesized Ag-NPs and Cu-NPs. The surface morphology, elemental description and size of particles were analyzed by scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy and zeta sizer (in addition polydispersity index and zeta potential). The justification for the preparation of particles was done by UV–Vis Spectroscopy (excitation peaks at 339 nm for copper and 415 nm for silver) and crystalline nature was observed by X-ray diffraction. Hence, the prepared particles are quite effective against soft rot pathogens in plants and can also be used effectively in some other multifunctional applications such as bioactive sport wear, surgical gowns, bioactive bandages and wrist or knee compression bandages, etc. [ABSTRACT FROM AUTHOR]

Several species of Thysanoptera are considered agricultural pests, especially Frankliniella occidentalis (Western Flower Thrips, WFT). The damage WFT causes to plants can either be direct by feeding and oviposition activity or indirect by WFT serving as vectors for several plant viruses, bacteria, and fungi. Properties of WFT like polyphagy, cryptic lifestyle, fast reproduction and the ability to quickly develop insecticide resistance make them difficult to control. Alternative pest management tactics are thus in high demand. Potential targets are the facultative or obligate endosymbionts that affect the life history parameters of WFT. The known endosymbionts of WFT: BFo1/BFo2 (B = bacteria, Fo = Frankliniella occidentalis, number indicate different types) positively influence their fertility and development. Elimination of these endosymbionts could result in a decreased individual reproduction level and decreased population growth. Bacteriophages specific against BFo1/BFo2 were isolated and characterized and were applied in a nochoice feeding assay to female WFT. Antibiotic and sugar solutions served as controls. Phage-treated thrips showed no significant difference in survival, fecundity, oviposition rate or developmental time of the progeny compared to the control, whereas antibiotic treatment caused a decline in survival, fecundity, and oviposition rate, but not in the developmental time of offspring. The results showed a rapid decline of the bacteriophage concentration in the feed solution, which the WFT salivary gland products might cause. The complex relationship between thrips, endosymbionts and bacteriophages, needs further attention before bacteriophages could be used as potential management tools. [ABSTRACT FROM AUTHOR]

Actinomycetes have long been recognized as an important source of antibacterial natural products. In recent years, actinomycetes in extreme environments have become one of the main research directions. Streptomyces sp. KN37 was isolated from the cold region of Kanas in Xinjiang. It demonstrated potent antimicrobial activity, but the primary active compounds remained unclear. Therefore, we aimed to combine genomics with traditional isolation methods to obtain bioactive compounds from the strain KN37. Whole-genome sequencing and KEGG enrichment analysis indicated that KN37 possesses the potential for synthesizing secondary metabolites, and 41 biosynthetic gene clusters were predicted, some of which showed high similarity to known gene clusters responsible for the biosynthesis of antimicrobial antibiotics. The traditional isolation methods and activity-guided fractionation were employed to isolate and purify seven compounds with strong bioactivity from the fermentation broth of the strain KN37. These compounds were identified as 4-(Diethylamino)salicylaldehyde (1), 4-Nitrosodiphenylamine (2), N-(2,4-Dimethylphenyl)formamide (3), 4-Nitrocatechol (4), Methylsuccinic acid (5), Phenyllactic acid (6) and 5,6-Dimethylbenzimidazole (7). Moreover, 4-(Diethylamino)salicylaldehyde exhibited the most potent inhibitory effect against Rhizoctonia solani, with an EC50 value of 14.487 mg/L, while 4-Nitrosodiphenylamine showed great antibacterial activity against Erwinia amylovora, with an EC50 value of 5.715 mg/L. This study successfully isolated several highly active antimicrobial compounds from the metabolites of the strain KN37, which could contribute as scaffolds for subsequent chemical synthesis. On the other hand, the newly predicted antibiotic-like substances have not yet been isolated, but they still hold significant research value. They are instructive in the study of active natural product biosynthetic pathways, activation of silent gene clusters, and engineering bacteria construction. [ABSTRACT FROM AUTHOR]

Objective. To characterize by microbiology the native strains associated to the intestinal tract of the species Panaque cochliodon. Materials and methods. Three adult specimens captured in the Magdalena River that were transported and sacrificed under animal welfare regulations were used. Dissection of the intestinal tract was performed, obtaining samples for microbiological isolation, using culture media, purifying the microorganisms, performing metabolic biochemical tests and API 20E (Biomeriux) tests for their identification. Results. Information on the microbial population structure was obtained, reporting the phylum Proteobacteria with the species: Pantoea sp, Erwinia sp, Providencia stuarti, Providencia alcalifaciens, Serratia ficaria, Citrobacter koseri and the phylum Firmicutes with the species: Bacillus sphaericus, Bacillus subtilis, Bacillus thurigiensis, Bacillus mycoides, Bacillus coagulans and Bacillus circulans. Conclusion. The predominant culturable microorganisms in P. cohliodon belong to the phylum Proteobacteria and the phylum Firmicutes. [ABSTRACT FROM AUTHOR]

Objetive/Background. The aim of this was to assess the diversity and antibiotic resistance of bacteria isolated from 19 crops with bacterial infection symptoms. Material and Methods: This collection was identified using 16S rRNA gene sequencing and the Biolog system. Susceptibility and minimum inhibitory concentration (MIC) for streptomycin, tetracycline, and gentamicin were determined using disk diffusion and E-test methods, respectively. Results: A total of 55 species belonging to 20 bacterial genera were identified, with Pseudomonas, Serratia, Pantoea, and Stenotrophomonas being the most abundant. Approximately 27% of the isolates were categorized as pathogenic through the hypersensitivity reaction test, including phytopathogenic species like Pseudomonas syringae, P. cichorii, Pantoea anthophila, P. stewartii, Stenotrophomonas maltophilia, Dickeya oryzae, Erwinia billingiae, Pectobacterium aroidearum, and Enterobacter cloacae subsp. dissolvens. Resistance to at least one antibiotic was detected in 60% of isolates from 17 crops, with tomatoes, heart of palm, and lettuce exhibited the highest proportion of resistant bacteria (>80%). Streptomycin resistance was most common (35%), followed by tetracycline (28%) and gentamicin (9%). Conclusions: The findings indicate the presence of antibiotic resistance in saprophytic and pathogenic bacteria associated with 17 out of 19 assessed crops, posing risks to the environment, phytosanitary conditions, and public health. [ABSTRACT FROM AUTHOR]

Fire blight, a disease of pome fruits caused by the bacterium Erwinia amylovora, has become increasingly difficult to manage after the emergence of streptomycin-resistant strains. Alternative antibiotics and copper are available; however, these chemicals have use restrictions in some countries and also can carry risks of phytotoxicity. Therefore, there is growing interest in biological-based management options, with bacteriophage (phages) showing promise, as these naturally occurring pathogens of bacteria are easy to isolate and grow. However, there are several technical challenges regarding the implementation of phage biocontrol in the field, as the viral molecules suffer from ultraviolet radiation (UVR) degradation and can die off rapidly in the absence of the host bacterium. In this work, we assessed the efficacy of Erwinia phages and a commercial phage product for blossom blight control in the field across multiple locations in the eastern United States. In these tests, disease control ranged from 0.0 to 82.7%, and addition of a UVR protectant only resulted in significantly increased disease control in 2 of 12 tests. We also analyzed microbial community population changes in response to phage application. Changes in bacterial community diversity metrics over time were not detected; however, relative abundances of target taxa were temporarily reduced after phage applications, indicating that these phage applications did not have deleterious effects on the flower microbiome. We have demonstrated that biological control of fire blight with phages is achievable, but a better understanding of phage-pathogen dynamics is required to optimize disease control efficacy. [ABSTRACT FROM AUTHOR]

The competitive colonization of bacteria on similar ecological niches has a significant impact during their establishment. The synthesis speeds of different chemical classes of molecules during early competitive colonization can reduce the number of competitors through metabolic effects. In this work, we demonstrate for the first time that Kosakonia cowanii Cp1 previously isolated from the seeds of Capsicum pubescens R. P. produced volatile organic compounds (VOCs) during competitive colonization against Pectobacterium aroidearum SM2, affecting soft rot symptoms in serrano chili (Capsicum annuum L.). The pathogen P. aroidearum SM2 was isolated from the fruits of C. annuum var. Serrano with soft rot symptoms. The genome of the SM2 strain carries a 5,037,920 bp chromosome with 51.46% G + C content and 4925 predicted protein-coding genes. It presents 12 genes encoding plant-cell-wall-degrading enzymes (PCDEWs), 139 genes involved in five types of secretion systems, and 16 genes related to invasion motility. Pathogenic essays showed soft rot symptoms in the fruits of C. annuum L., Solanum lycopersicum, and Physalis philadelphica and the tubers of Solanum tuberosum. During the growth phases of K. cowanii Cp1, a mix of VOCs was identified by means of HS-SPME-GC-MS. Of these compounds, 2,5-dimethyl-pyrazine showed bactericidal effects and synergy with acetoin during the competitive colonization of K. cowanii Cp1 to completely reduce soft rot symptoms. This work provides novel evidence grounding a better understanding of bacterial interactions during competitive colonization on plant tissue, where VOC synthesis is essential and has a high potential capacity to control pathogenic microorganisms in agricultural systems. [ABSTRACT FROM AUTHOR]

We induced immune activation in mass rearing experiments in three insect species, i.e., Gryllus bimaculatus De Geer, 1773 (Orthoptera: Gryllidae), Hermetia illucens (Linnaeus, 1758) (Diptera: Stratiomyidae), and Protaetia brevitarsis seulensis (Kolbe, 1886) (Coleoptera: Scarabaeidae). Lysosomal staining of immune cells was a little over 6% in the control group insects, whereas it ranged from 17-35% in insects immunized with Escherichia coli K12 or Bacillus thuringiensis (Bt). The expression of attacin-like protein and defensin-like protein was also found to be upregulated at least 10-fold, and even up to 30-fold, from the third day of rearing in insects immunized with E. coli K12 or Bt. Non-immunized or immunized G. bimaculatus, H. illucens, and P. brevitarsis seulensis were freeze-dried and powdered, and these powders were then tested for protection against Pectobacterium carotovorum infestation. No inhibitory effects on P. carotovorum were observed when using all non-immunized insect powders or PBS. However, in the clear zone test treated with H. illucens powder at 10,000 ppm, an average size of 21.67 mm was observed. In a test using potato slices infected with P. carotovorum, we observed severe disease occurrence and potato weight loss in all non-immunized insect powders or PBS-treated groups. However, the group treated with H. illucens powder had the least potato weight loss. When tested on lettuce, the H. illucens powder-treated group revealed an approximately 10% increase in the fresh weight of lettuce, with both the dry weight and leaf area of lettuce increasing in comparison with those in the control group. Thus, our study proposes a novel method for the use of freeze-dried and powdered forms of insects immunized in mass rearing as effective functional fertilizers on a large scale that can also be effective in inhibiting microbial infections, overcoming the limitation of high production costs of such insect fertilizers using conventional methods. [ABSTRACT FROM AUTHOR]

Fire blight, caused by the bacterium Erwinia amylovora, is a major threat to pear production worldwide. Bacteriophages, viruses that infect bacteria, are a promising alternative to antibiotics for controlling fire blight. In this study, we isolated a novel bacteriophage, RH-42-1, from Xinjiang, China. We characterized its biological properties, including host range, plaque morphology, infection dynamics, stability, and sensitivity to various chemicals. RH-42-1 infected several E. amylovora strains but not all. It produced clear, uniform plaques and exhibited optimal infectivity at a multiplicity of infection (MOI) of 1, reaching a high titer of 9.6 × 109 plaque-forming units (PFU)/mL. The bacteriophage had a short latent period (10 min), a burst size of 207 PFU/cell, and followed a sigmoidal one-step growth curve. It was stable at temperatures up to 60 °C but declined rapidly at higher temperatures. RH-42-1 remained viable within a pH range of 5 to 9 and was sensitive to extreme pH values. The bacteriophage demonstrates sustained activity upon exposure to ultraviolet radiation for 60 min, albeit with a marginal reduction. In our assays, it exhibited a certain level of resistance to 5% chloroform (CHCl3), 5% isopropanol (C3H8O), and 3% hydrogen peroxide (H2O2), which had little effect on its activity, whereas it showed sensitivity to 75% ethanol (C2H5OH). Electron microscopy revealed that RH-42-1 has a tadpole-shaped morphology. Its genome size is 14,942 bp with a GC content of 48.19%. Based on these characteristics, RH-42-1 was identified as a member of the Tectiviridae family, Alphatectivirus genus. This is the first report of a bacteriophage in this genus with activity against E. amylovora. [ABSTRACT FROM AUTHOR]

Plants are exposed to various stressors, including pathogens, requiring specific environmental conditions to provoke/induce plant disease. This phenomenon is called the "disease triangle" and is directly connected with a particular plant–pathogen interaction. Only a virulent pathogen interacting with a susceptible plant cultivar will lead to disease under specific environmental conditions. This may seem difficult to accomplish, but soft rot Pectobacteriaceae (SRPs) is a group virulent of pathogenic bacteria with a broad host range. Additionally, waterlogging (and, resulting from it, hypoxia), which is becoming a frequent problem in farming, is a favoring condition for this group of pathogens. Waterlogging by itself is an important source of abiotic stress for plants due to lowered gas exchange. Therefore, plants have evolved an ethylene-based system for hypoxia sensing. Plant response is coordinated by hormonal changes which induce metabolic and physiological adjustment to the environmental conditions. Wetland species such as rice (Oryza sativa L.), and bittersweet nightshade (Solanum dulcamara L.) have developed adaptations enabling them to withstand prolonged periods of decreased oxygen availability. On the other hand, potato (Solanum tuberosum L.), although able to sense and response to hypoxia, is sensitive to this environmental stress. This situation is exploited by SRPs which in response to hypoxia induce the production of virulence factors with the use of cyclic diguanylate (c-di-GMP). Potato tubers in turn reduce their defenses to preserve energy to prevent the negative effects of reactive oxygen species and acidification, making them prone to soft rot disease. To reduce the losses caused by the soft rot disease we need sensitive and reliable methods for the detection of the pathogens, to isolate infected plant material. However, due to the high prevalence of SRPs in the environment, we also need to create new potato varieties more resistant to the disease. To reach that goal, we can look to wild potatoes and other Solanum species for mechanisms of resistance to waterlogging. Potato resistance can also be aided by beneficial microorganisms which can induce the plant's natural defenses to bacterial infections but also waterlogging. However, most of the known plant-beneficial microorganisms suffer from hypoxia and can be outcompeted by plant pathogens. Therefore, it is important to look for microorganisms that can withstand hypoxia or alleviate its effects on the plant, e.g., by improving soil structure. Therefore, this review aims to present crucial elements of potato response to hypoxia and SRP infection and future outlooks for the prevention of soft rot disease considering the influence of environmental conditions. [ABSTRACT FROM AUTHOR]

A rapid, eco-friendly, and simple method for the synthesis of long-lasting (2 years) silver nanoparticles (AgNPs) is reported using aqueous leaf and petal extracts of Tagetes erecta L. The particles were characterized using UV-Visible spectrophotometry and the analytical and crystallographic techniques of transmission electron microscopy (TEM). The longevity of the AgNPs was studied using UV-Vis and high-resolution TEM. The antibacterial activity of the particles against Erwinia amylovora was evaluated using the Kirby–Bauer disk diffusion method. The results were analyzed using ANOVA and Tukey's test (p ≤ 0.05). Both the leaf and petal extracts produced AgNPs, but the leaf extract (1 mL) was long-lasting and quasi-spherical (17.64 ± 8.87 nm), with an absorbance of UV-Vis λmax 433 and a crystalline structure (fcc, 111). Phenols, flavonoids, tannins, and terpenoids which are associated with -OH, C=O, and C=C were identified in the extracts and could act as reducing and stabilizing agents. The best antibacterial activity was obtained with a nanoparticle concentration of 50 mg AgNPs L−1. The main contribution of the present research is to present a sustainable method for producing nanoparticles which are stable for 2 years and with antibacterial activity against E. amylovora, one of most threatening pathogens to pear and apple productions. [ABSTRACT FROM AUTHOR]

Chinese flowering cabbage is an important bolting stem vegetable widely grown in southern China, but severe losses caused by soft rot disease are very common in this crop. The MYB transcription factor (TF) family is the largest TF family in plants and plays diverse roles in response to stresses. However, the responses of MYB TFs to biotic stress in Chinese flowering cabbage have not been systematically studied. Herein, 255 R2R3-MYB genes were identified in the genome of Chinese flowering cabbage and classified into 29 subgroups based on phylogenetic comparisons with Arabidopsis thaliana. Gene duplication events involved 182 gene duplication pairs, and we found that two tandem duplication events involving R2R3-MYB genes in Chinese flowering cabbage may also affect gene family expansion. Transcriptome data analysis indicated that MYB TF genes are highly enriched in differentially expressed gene (DEG) sets. Combined with phylogenetic and transcriptome analysis, we identified 12 R2R3-MYB genes that potentially play a role in the response to soft rot stress. Our research provides a foundation for further research on the response of R2R3-MYB genes to soft rot stress in Chinese flowering cabbage. [ABSTRACT FROM AUTHOR]

This study investigates the use of a barley-associated Erwinia gerundensis strain as a biocontrol agent for the protection of malt against fungal development and mycotoxin production during the malting of barley. First, the antifungal activity of E. gerundensis was studied via simultaneous co-cultures in Yeast Malt broth and on barley kernels artificially infected with Fusarium tricinctum. Then, the effect of E. gerundensis on the fungal load and mycotoxin content of malt obtained from naturally contaminated barley was studied by applying different doses of the bacterial strain at the steeping step of the malting process. Mycotoxin concentrations were determined using the technique of liquid chromatography coupled to the mass spectrometry detector in tandem (LC-MS/MS). Also, the effect of E. gerundensis on the technological quality of the final malt was evaluated using European Brewery Convention standard methods. The bacterial strain reduced the production of enniatin (ENN) by 97.7–99.8% and 38–68% in the liquid medium and on barley kernels, respectively, along with 0–82% Fusarium tricinctum growth reduction on barley kernels. Application of E. gerundensis at the beginning of the steeping step reduced the fungal load of the final malt by 67–72% and its ENN and deoxynivalenol (DON) contents by 32–50% and 15–33%, respectively, depending on the treatment dose. Barley malts treated with E. gerundensis showed no degradation in their technological quality, thus making E. gerundensis a potentially interesting biocontrol agent for the malting and brewing industries. Further investigation should be focused on improving the bioprotective capability of the proposed biocontrol agent. [ABSTRACT FROM AUTHOR]

The type VI secretion system (T6SS) assembles into a contractile nanomachine to inject effectors across bacterial membranes for secretion. The Agrobacterium tumefaciens species complex is a group of soil inhabitants and phytopathogens that deploys T6SS as an antibacterial weapon against bacterial competitors at both inter-species and intra-species levels. The A. tumefaciens strain 1D1609 genome encodes one main T6SS gene cluster and four vrgG genes (i.e., vgrGa-d), each encoding a spike protein as an effector carrier. A previous study reported that vgrGa-associated gene 2, named v2a, encodes a His-Me finger nuclease toxin (also named HNH/ENDO VII nuclease), contributing to DNase-mediated antibacterial activity. However, the functions and roles of other putative effectors remain unknown. In this study, we identified vgrGc-associated gene 2 (v2c) that encodes another His-Me finger nuclease but with a distinct Serine Histidine Histidine (SHH) motif that differs from the AHH motif of V2a. We demonstrated that the ectopic expression of V2c caused growth inhibition, plasmid DNA degradation, and cell elongation in Escherichia coli using DNAse activity assay and fluorescence microscopy. The cognate immunity protein, V3c, neutralizes the DNase activity and rescues the phenotypes of growth inhibition and cell elongation. Ectopic expression of V2c DNase-inactive variants retains the cell elongation phenotype, while V2a induces cell elongation in a DNase-mediated manner. We also showed that the amino acids of conserved SHH and HNH motifs are responsible for the V2c DNase activity in vivo and in vitro. Notably, V2c also mediated the DNA degradation and cell elongation of the target cell in the context of interbacterial competition. Importantly, V2a and V2c exhibit different capacities against different bacterial species and function synergistically to exert stronger antibacterial activity against the soft rot phytopathogen, Dickeya dadantii. [ABSTRACT FROM AUTHOR]

Homologous recombination is a major force mechanism driving bacterial evolution, host adaptability, and acquisition of novel virulence traits. Pectobacterium parmentieri is a plant bacterial pathogen distributed worldwide, primarily affecting potatoes, by causing soft rot and blackleg diseases. The goal of this investigation was to understand the impact of homologous recombination on the genomic evolution of P. parmentieri. Analysis of P. parmentieri genomes using Roary revealed a dynamic pan-genome with 3,742 core genes and over 55% accessory genome variability. Bayesian population structure analysis identified 7 lineages, indicating species heterogeneity. ClonalFrameML analysis displayed 5,125 recombination events, with the lineage 4 exhibiting the highest events. fastGEAR analysis identified 486 ancestral and 941 recent recombination events ranging from 43 bp to 119 kb and 36 bp to 13.96 kb, respectively, suggesting ongoing adaptation. Notably, 11% (412 genes) of the core genome underwent recent recombination, with lineage 1 as the main donor. The prevalence of recent recombination (double compared to ancient) events implies continuous adaptation, possibly driven by global potato trade. Recombination events were found in genes involved in vital cellular processes (DNA replication, DNA repair, RNA processing, homeostasis, and metabolism), pathogenicity determinants (type secretion systems, cell-wall degrading enzymes, iron scavengers, lipopolysaccharides (LPS), flagellum, etc.), antimicrobial compounds (phenazine and colicin) and even CRISPR-Cas genes. Overall, these results emphasize the potential role of homologous recombination in P. parmentieri 's evolutionary dynamics, influencing host colonization, pathogenicity, adaptive immunity, and ecological fitness. [ABSTRACT FROM AUTHOR]

Honeydew from Hemipteran insects serves as carbohydrate source to beneficial insects but also to various microorganisms. Microbial volatile organic compounds (mVOCs) may play diverse roles in herbivore–microbe–natural enemy interactions. However, the functional significance of mVOCs from aphid honeydew remains largely unclear. In this study, a total of seven cultivable bacteria from Sitobion miscanthi honeydew have been isolated and identified based on 16S rRNA technique, which included Lysinibacillus fusiformis, Erwinia aphidicola, E. tasmaniensis, Acinetobacter bereziniae, Klebsiella quasipneumoniae subsp. Similipneumoniae, Staphylococcus capitis and Bacillus safensis subsp. safensis. One bacterial strain, L. fusiformis MH1, was found to be most attractive to Aphidius gifuensis parasitic wasp in Y-tube olfactometer. Two compounds, namely 1-ethyl-2-methylbenzene and 2-butyl-1-octanol, were emitted from L. fusiformis MH1 and were attractive to A. gifuensis and identified by using coupled gas chromatography–electroantennography and coupled gas chromatography with mass spectrometry. Application of bacterial and mVOCs formulations in crop field resulted in significant aphid abundance decrease associated with higher parasitism rates compared with control. Our results indicated that some microbes in aphid honeydew could manipulate the herbivore–natural enemy interactions and could be developed as a novel alternative for environmentally friendly biological control of aphids. [ABSTRACT FROM AUTHOR]

BACKGROUND: Quorum sensing inhibitors (QSIs) are an emerging control tool that inhibits the quorum sensing (QS) system of pathogenic bacteria. We aimed to screen for potential QSIs in the metabolites of Trichoderma and to explore their inhibitory mechanisms. RESULTS: We screened a strain of Trichoderma asperellum LN004, which demonstrated the ability to inhibit the color development of Chromobacterium subtsugae CV026, primarily attributed to the presence of emodin as its key QSI component. The quantitative polymerase chain reaction with reverse transcription results showed that after emodin treatment of Pectobacterium carotovorum subsp. carotovorum (Pcc), plant cell wall degrading enzyme‐related synthetic genes were significantly downregulated, and the exogenous enzyme synthesis gene negative regulator (rsmA) was upregulated 3.5‐fold. Docking simulations indicated that emodin could be a potential ligand for ExpI and ExpR proteins because it exhibited stronger competition than the natural ligands in Pcc. In addition, western blotting showed that emodin attenuated the degradation of n‐acylhomoserine lactone on the ExpR protein and protected it. Different concentrations of emodin reduced the activity of pectinase, cellulase, and protease in Pcc by 20.81%–72.21%, 8.38%–52.73%, and 3.57%–47.50%. Lesion size in Chinese cabbages, carrots and cherry tomatoes following Pcc infestation was reduced by 10.02%–68.57%, 40.17%–88.56% and 11.36%–86.17%. CONCLUSION: Emodin from T. asperellum LN004 as a QSI can compete to bind both ExpI and ExpR proteins, interfering with the QS of Pcc and reducing the production of virulence factors. The first molecular mechanism reveals the ability of emodin as a QSI to competitively inhibit two QS proteins simultaneously. © 2023 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

This article is an editorial published in Frontiers in Microbiology titled "Biology of myxobacteria." It discusses the unique biological features of myxobacteria, which are soil-dwelling organisms that exhibit complex communication and predation behaviors. The article highlights the role of myxobacteria in shaping microbial communities and their potential as biological control agents for protecting crops. It also explores the overlap between developmental biology, predation biology, and myxobacterial ecology. The editorial summarizes several research articles and reviews that contribute to our understanding of myxobacterial biology and their applications in various fields. [Extracted from the article]

Introduction: The development of agriculture in terms of sustainability and low environmental impact is, at present, a great challenge, mainly in underdeveloped and marginal geographical areas. The Salvia rosmarinus "Eretto Liguria" ecotype is widespread in Liguria (Northwest Italy), and farmers commonly use it by for cuttings and for marketing. In the present study, this ecotype was characterized in comparison with other cultivars from the same geographical region and Campania (Southern Italy), with a view to application and registration processes for the designation of protected geographical indications. Moreover, the possibility of using the resulting biomass after removing cuttings or fronds as a source of extracts and pure compounds to be used as phytosanitary products in organic farming was evaluated. Specifically, the potential of rosemary extracts and pure compounds to prevent soft rot damage was then tested. Methods: A targeted NMR metabolomic approach was employed, followed by multivariate analysis, to characterize the rosemary accessions. Bacterial soft rot assay and disk diffusion test were carried out to evaluate the activity of extracts and isolated compounds against Pectobacterium carotovorum subsp. carotovorum. Enzymatic assay was performed to measure the in vitro inhibition of the pectinase activity produced by the selected pathogen. Molecular docking simulations were used to explore the possible interaction of the selected compounds with the pectinase enzymes. Results and Discussion: The targeted metabolomic analysis highlighted those different geographical locations can influence the composition and abundance of bioactive metabolites in rosemary extracts. At the same time, genetic factors are important when a single geographical area is considered. Self-organizing maps (SOMs) showed that the accessions of "Eretto Liguria" appeared well characterized when compared to the others and had a good content in specialized metabolites, particularly carnosic acid. Soft rotting Enterobacteriaceae belonging to the Pectobacterium genus represent a serious problem in potato culture. Even though rosemary methanolic extracts showed a low antibacterial activity against a strain of Pectobacterium carotovorum subsp. carotovorum in the disk diffusion test, they showed ability in reducing the soft rot damage induced by the bacterium on potato tissue. 7-Omethylrosmanol, carnosol and isorosmanol appeared to be the most active components. In silico studies indicated that these abietane diterpenoids may interact with P. carotovorum subsp. carotovorum pectate lyase 1 and endopolygalacturonase, thus highlighting these rosemary components as starting points for the development of agents able to prevent soft rot progression. [ABSTRACT FROM AUTHOR]