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Aggregatibacter actinomycetemcomitans ApiA is a trimeric autotransporter outer membrane protein (Omp) that participates in multiple functions, enabling A. actinomycetemcomitans to adapt to a variety of environments. The goal of this study is to identify regions in the apiA gene responsible for three of these functions: auto-aggregation, buccal epithelial cell binding, and complement resistance. Initially, apiA was expressed in Escherichia coli. Finally, wild-type A. actinomycetemcomitans and an apiA-deleted version were tested for their expression in the presence and absence of serum and genes related to stress adaptation, such as oxygen regulation, catalase activity, and Omp proteins. Sequential deletions in specific regions in the apiA gene as expressed in E. coli were examined for membrane proteins, which were confirmed by microscopy. The functional activity of epithelial cell binding, auto-aggregation, and complement resistance were then assessed, and regions in the apiA gene responsible for these functions were identified. A region spanning amino acids 186–217, when deleted, abrogated complement resistance and Factor H (FH) binding, while a region spanning amino acids 28–33 was related to epithelial cell binding. A 13-amino-acid peptide responsible for FH binding was shown to promote serum resistance. An apiA deletion in a clinical isolate (IDH781) was created and tested in the presence and/or absence of active and inactive serum and genes deemed responsible for prominent functional activity related to A. actinomycetemcomitans survival using qRT-PCR. These experiments suggested that apiA expression in IDH781 is involved in global regulatory mechanisms that are serum-dependent and show complement resistance. This is the first study to identify specific apiA regions in A. actinomycetemcomitans responsible for FH binding, complement resistance, and other stress-related functions. Moreover, the role of apiA in overall gene regulation was observed. [ABSTRACT FROM AUTHOR]

Summary: From recent literature and research studies, it has been found that some bacterial strains have abilities with probiotic activities to produce B vitamins, which play essential roles in maintaining human health. Oligosaccharides can promote the beneficial microbes, however, the specific effects of oligosaccharides on B vitamins‐producing ability of probiotic strains have not been clarified. This study evaluated the effect of different oligosaccharides on the probiotic properties and B vitamin‐producing ability of 21 selected probiotic strains. The obtained results suggested that the strains could utilise oligosaccharides as the sole carbon source, and the hydrophobicity, auto‐aggregation, and biofilm formation of probiotic strains were specific regulated after fermentation with different oligosaccharides. In particular, the oligosaccharides had different influences on the levels of extracellular B vitamins produced by probiotic strains. These findings provide the foundation for studies on the B vitamins‐producing probiotic strains and their application in functional foods to prevent B vitamins deficiency. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the ability of twelve strains of Enterococcus spp. to form biofilms on stainless steel (AISI 316 L and AISI 304 L) and to characterize the physicochemical properties of the bacterial and surface supports. The study also examined the auto-aggregation and extracellular polymeric substances of strains in both planktonic and sessile forms. The results showed that all Enterococcus spp. strains tested were capable of forming biofilms, with varying degrees reaching 7.41 log CFU/cm2 on AISI 316 L for Enterococcus mundtii A1. On AISI 304 L, the highest biofilm recorded was 7.01 log CFU/cm2 for Enterococcus mundtii A13. It was observed that auto-aggregation was influenced by the strains' hydrophobicity. These results shed light on the possible application of Enterococcus spp. biofilm as a strategy to control pathogenic biofilms in various industries and provide insight into the role of physicochemical properties in biofilm formation. [ABSTRACT FROM AUTHOR]

Aggregatibacter actinomycetemcomitans ApiA is a trimeric autotransporter outer membrane protein (Omp) that participates in multiple functions, enabling A. actinomycetemcomitans to adapt to a variety of environments. The goal of this study is to identify regions in the apiA gene responsible for three of these functions: auto-aggregation, buccal epithelial cell binding, and complement resistance. Initially, apiA was expressed in Escherichia coli. Finally, wild-type A. actinomycetemcomitans and an apiA-deleted version were tested for their expression in the presence and absence of serum and genes related to stress adaptation, such as oxygen regulation, catalase activity, and Omp proteins. Sequential deletions in specific regions in the apiA gene as expressed in E. coli were examined for membrane proteins, which were confirmed by microscopy. The functional activity of epithelial cell binding, auto-aggregation, and complement resistance were then assessed, and regions in the apiA gene responsible for these functions were identified. A region spanning amino acids 186–217, when deleted, abrogated complement resistance and Factor H (FH) binding, while a region spanning amino acids 28–33 was related to epithelial cell binding. A 13-amino-acid peptide responsible for FH binding was shown to promote serum resistance. An apiA deletion in a clinical isolate (IDH781) was created and tested in the presence and/or absence of active and inactive serum and genes deemed responsible for prominent functional activity related to A. actinomycetemcomitans survival using qRT-PCR. These experiments suggested that apiA expression in IDH781 is involved in global regulatory mechanisms that are serum-dependent and show complement resistance. This is the first study to identify specific apiA regions in A. actinomycetemcomitans responsible for FH binding, complement resistance, and other stress-related functions. Moreover, the role of apiA in overall gene regulation was observed.

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In this study, the antibiofilm activity of ethanol, acetone, and ethyl acetate extracts of Lamium album was evaluated against nine clinical strains from human wound swabs and two reference strains. The extracts of L. album exhibited significant antibiofilm activity. The extracts inhibited cell attachment and subsequent biofilm formation. The activity was dose-and strain-dependent, which was confirmed by fluorescence microscopy. The effects on mature biofilms were lower. In addition, the results showed a decrease in bacterial auto-aggregation in the presence of the extracts and no motility reduction. Phytochemical analysis and identification of functional groups by using Fourier Transform Infrared Spectroscopy were also performed. The results obtained in this study provide a basis for further research on this plant species.

The properties of intestinal bacteria/probiotics, such as cell surface hydrophobicity (CSH), auto-aggregation, and biofilm formation ability, play an important role in shaping the relationship between the bacteria and the host. The current study aimed to investigate the cell surface properties of fish intestinal bacteria and probiotics. Microbial adhesion to hydrocarbons was tested according to Kos and coauthors. The aggregation abilities of the investigated strains were studied as described by Collado and coauthors. The ability of bacterial isolates to form a biofilm was determined by performing a qualitative analysis using crystal violet staining based on the attachment of bacteria to polystyrene. These studies prove that bacterial cell surface hydrophobicity (CSH) is associated with the growth medium, and the effect of the growth medium on CSH is species-specific and likely also strain-specific. Isolates of intestinal lactobacilli from fish (Salmo ischchan) differed from isolates of non-fish/shrimp origin in the relationship between auto-aggregation and biofilm formation. Average CSH levels for fish lactobacilli and E. coli might were lower compared to those of non-fish origin, which may affect the efficiency of non-fish probiotics use in fisheries due to the peculiarities of the hosts' aquatic lifestyles. [ABSTRACT FROM AUTHOR]

Copyright of Environmental Science & Technology (10036504) is the property of Editorial Board of Environmental Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To effectively separate and collect microalgal particles from a water body without using a chemical coagulant, a series of flotation separation experiments were conducted during the auto-flocculation life cycle phase addressing a problem in separated algal biomass recycling. Based on the analysis of extracellular polymeric substances (EPS), which participate in algae particle auto-flocculation, we investigated the role of EPS and evaluated its applicability as a chemical coagulant substitute in the flotation process. The sources of the main algal growth factors, carbon, nitrogen, phosphorus, and light intensity, were controlled to compare the differences in EPS components and separation efficiency among the cultivation samples. Comparative analysis of proteins and carbohydrates revealed no qualitative difference in the EPS affecting the auto-flocculation and flotation separation of particles. However, there was a slight difference in the quantitative EPS concentration by culture condition, and under high EPS carbohydrate concentration, a high separation efficiency was achieved under nutrient-deficient conditions. Moreover, the supply of CO2 gas in a nutrient-deficient state promoted EPS production and increased the carbohydrate content, which induced algae particle hydrophobicity and promoted increased flotation efficiency. The study results suggested that microalgae particles can be separated in an eco-friendly manner using only EPS emitted by microalgae during auto-flocculation without a chemical coagulant during flotation. [ABSTRACT FROM AUTHOR]

The study aimed to evaluate the effect of thermal inactivation of potentially probiotic lactic acid bacteria (LAB) strains isolated from food on their ability to compete with pathogenic microorganisms. Five strains of LAB, previously isolated from food and characterized, one commercial reference strain of Lactiplantibacillus plantarum 299v, and two indicator strains of Staphylococcus aureus 25923 and Listeriamonocytogenes 15313 were used in the study. The experiment consisted in applying a stress factor (high temperature: 80 °C, at a different time: 5, 15, and 30 min) to the tested LAB cells to investigate the in vitro properties such as hydrophobicity abilities (against p-xylene and n-hexadecane), auto-aggregation, co-aggregation with pathogens, and inhibition of pathogens adhesion to the porcine gastric mucin. The bacterial strains showed various hydrophobicity to p-xylene (36–73%) and n-hexadecane (11–25%). The affinity for solvents expanded with increasing thermal inactivation time. All LAB isolates were able to auto-aggregate (ranging from 17 to 49%). Bacterial strains subjected to 5 and 15 min of thermal inactivation had the highest auto-aggregation ability in comparison to viable and heat-killed cells for 30 min. The LAB strains co-aggregated with pathogens to different degrees; among them, the highest scores of co-aggregation were observed for L. monocytogenes, reaching 27% (with 15 min of heat-killed LAB cells). All LAB strains reduced the adherence of pathogenic bacteria in the competition test, moreover, heat-killed cells (especially 15 min inactivated) were more efficient than viable cells. The properties of selected LAB strains as moderately heat-stressed forms analyzed in the study increased the prevention of colonization and elimination of pathogenic bacteria in the in vitro model of gastrointestinal tract. The thermal inactivation process may therefore preserve and modifies some characteristics of bacterial cells. [ABSTRACT FROM AUTHOR]

Abstract Background Auto-aggregation is a desired property for probiotic strains because it is suggested to promote colonization of the human intestine, to prevent pathogen infections and to modulate the colonic mucosa. We recently reported the generation of adapted mutants of Lactiplantibacillus plantarum NZ3400, a derivative of the model strain WCFS1, for colonization under adult colonic conditions of PolyFermS continuous intestinal fermentation models. Here we describe and characterize the emerge of an auto-aggregating phenotype in L. plantarum NZ3400 derivatives recovered from the modelled gut microbiota. Results L. plantarum isolates were recovered from reactor effluent of four different adult microbiota and from spontaneously formed reactor biofilms. Auto-aggregation was observed in L. plantarum recovered from all microbiota and at higher percentage when recovered from biofilm than from effluent. Further, auto-aggregation percentage increased over time of cultivation in the microbiota. Starvation of the gut microbiota by interrupting the inflow of nutritive medium enhanced auto-aggregation, suggesting a link to nutrient availability. Auto-aggregation was lost under standard cultivation conditions for lactobacilli in MRS medium. However, it was reestablished during growth on sucrose and maltose and in a medium that simulates the abiotic gut environment. Remarkably, none of these conditions resulted in an auto-aggregation phenotype in the wild type strain NZ3400 nor other non-aggregating L. plantarum, indicating that auto-aggregation depends on the strain history. Whole genome sequencing analysis did not reveal any mutation responsible for the auto-aggregation phenotype. Transcriptome analysis showed highly significant upregulation of LP_RS05225 (msa) at 4.1–4.4 log2-fold-change and LP_RS05230 (marR) at 4.5–5.4 log2-fold-change in all auto-aggregating strains compared to non-aggregating. These co-expressed genes encode a mannose-specific adhesin protein and transcriptional regulator, respectively. Mapping of the RNA-sequence reads to the promoter region of the msa-marR operon reveled a DNA inversion in this region that is predominant in auto-aggregating but not in non-aggregating strains. This strongly suggests a role of this inversion in the auto-aggregation phenotype. Conclusions L. plantarum NZ3400 adapts to the in vitro colonic environment by developing an auto-aggregation phenotype. Similar aggregation phenotypes may promote gut colonization and efficacy of other probiotics and should be further investigated by using validated continuous models of gut fermentation such as PolyFermS.

The impact of high concentrations of heavy metals and the loss of functional microorganisms usually affect the nitrogen removal process in wastewater treatment systems. In the study, a unique auto-aggregating aerobic denitrifier (Pseudomonas stutzeri strain YC-34) was isolated with potential applications for Cr(VI) biosorption and reduction. The nitrogen removal efficiency and denitrification pathway of the strain were determined by measuring the concentration changes of inorganic nitrogen during the culture of the strain and amplifying key denitrification functional genes. The changes in auto-aggregation index, hydrophobicity index, and extracellular polymeric substances (EPS) characteristic index were used to evaluate the auto-aggregation capacity of the strain. Further studies on the biosorption ability and mechanism of cadmium in the process of denitrification were carried out. The changes in tolerance and adsorption index of cadmium were measured and the micro-characteristic changes on the cell surface were analyzed. The strain exhibited excellent denitrification ability, achieving 90.58% nitrogen removal efficiency with 54 mg/L nitrate-nitrogen as the initial nitrogen source and no accumulation of ammonia and nitrite-nitrogen. Thirty percentage of the initial nitrate-nitrogen was converted to N2, and only a small amount of N2O was produced. The successful amplification of the denitrification functional genes, norS, norB, norR, and nosZ, further suggested a complete denitrification pathway from nitrate to nitrogen. Furthermore, the strain showed efficient aggregation capacity, with the auto-aggregation and hydrophobicity indices reaching 78.4 and 75.5%, respectively. A large amount of protein-containing EPS was produced. In addition, the strain effectively removed 48.75, 46.67, 44.53, and 39.84% of Cr(VI) with the initial concentrations of 3, 5, 7, and 10 mg/L, respectively, from the nitrogen-containing synthetic wastewater. It also could reduce Cr(VI) to the less toxic Cr(III). FTIR measurements and characteristic peak deconvolution analysis demonstrated that the strain had a robust hydrogen-bonded structure with strong intermolecular forces under the stress of high Cr(VI) concentrations. The current results confirm that the novel denitrifier can simultaneously remove nitrogen and chromium and has potential applications in advanced wastewater treatment for the removal of multiple pollutants from sewage. [ABSTRACT FROM AUTHOR]

[Display omitted] • Granulation and SND efficiency in AGS system was promoted by adding strain XL-2. • The addition of strain XL-2 promoted EPS secretion, particularly PN. • The increase of PN promoted hydrophilicity and altered proteins secondary structures. • Strain XL-2 induced the enrichment of EPS producing and denitrifying bacteria. In this study, the possibility of an auto-aggregating bacterium Pseudomonas strain XL-2 with heterotrophic nitrification-aerobic denitrification capacity for improving granulation and nitrogen removal was evaluated. The results showed that the supplementation of strain XL-2 promoted granulation, making R1 (experimental group with strain XL-2) dominated by granules at 14 d, which was 12 days earlier than R2 (control group without strain XL-2). This was attributed to the promotion of extracellular polymeric substances (EPS) secretion, particularly proteins by adding strain XL-2, thereby improving the hydrophobicity of sludge and altering the proteins secondary structures to facilitate aggregation. Meanwhile, adding strain XL-2 improved simultaneous nitrification and denitrification efficiency of R1. Microbial community analysis indicated that strain XL-2 successfully proliferated in aerobic granule sludge and might induce the enrichment of genera such as Flavobacterium and Paracoccus that were favorable for EPS secretion and denitrification, jointly promoting granulation and enhancing nitrogen removal efficiency. [ABSTRACT FROM AUTHOR]

Chestnut honey has been used as ethnomedicine. Probiotics are defined as live microorganisms that can provide a health benefit, impeding the development of several health conditions and diseases, including cancer. This study aims to investigate the effects of chestnut honey on probiotic bacteria and the in vitro cytotoxic effects of the combination of probiotics and chestnut honey on cancer cells. First, the effects of chestnut honey on the growth of bacteria were examined, followed by its effects on the probiotic properties of Lactobacillus acidophilus LA-5 and Lactobacillus rhamnosus GG. Once the bacteria had grown on chestnut honey, the in vitro cytotoxic effects on breast and colon cancer cell lines, MCF-7 and Caco-2, respectively, and a non-cancerous breast epithelial cell line, MCF-10A, were investigated. Chestnut honey positively affected the probiotic bacteria by increasing the growth and modulating probiotic properties such as autoaggregation and surface hydrophobicity. Furthermore, probiotics grown on chestnut honey had more cytotoxic effects on the cancer cell lines than probiotics or honey alone. The present study showed that new combinations of honey and probiotics have the potential to formulate new nutraceuticals.

The properties of intestinal bacteria/probiotics, such as cell surface hydrophobicity (CSH), auto-aggregation, and biofilm formation ability, play an important role in shaping the relationship between the bacteria and the host. The current study aimed to investigate the cell surface properties of fish intestinal bacteria and probiotics. Microbial adhesion to hydrocarbons was tested according to Kos and coauthors. The aggregation abilities of the investigated strains were studied as described by Collado and coauthors. The ability of bacterial isolates to form a biofilm was determined by performing a qualitative analysis using crystal violet staining based on the attachment of bacteria to polystyrene. These studies prove that bacterial cell surface hydrophobicity (CSH) is associated with the growth medium, and the effect of the growth medium on CSH is species-specific and likely also strain-specific. Isolates of intestinal lactobacilli from fish (Salmo ischchan) differed from isolates of non-fish/shrimp origin in the relationship between auto-aggregation and biofilm formation. Average CSH levels for fish lactobacilli and E. coli might were lower compared to those of non-fish origin, which may affect the efficiency of non-fish probiotics use in fisheries due to the peculiarities of the hosts’ aquatic lifestyles.

The antagonistic effect of probiotics against oral pathogens merits exploration because these bacteria are beneficial to the host's health. The antimicrobial activity of two probiotic strains, Lactobacillus casei and Lactobacillus salivarius, as well as L. casei and L. salivarius combination (1:1), was investigated against Streptococcus mutans, Streptococcus sobrinus, Candida albicans, Candida glabrata and Candida tropicalis using agar-well diffusion, auto-aggregation and coaggregation assays. L. salivarius cell-free supernatant (CFS) alone exhibited greater inhibitory effect against Streptococci spp. compared to L. casei CFS alone and the combination. However, no inhibition was observed for Candida spp. L. salivarius alone exhibited significantly stronger auto-aggregation than L. casei alone (p = 0.05) and L. casei and L. salivarius combination. L. salivarius exhibited strong coaggregation ability with Candida spp., followed by Streptococci spp. while L. casei exhibited coaggregation only with Streptococci spp. However, L. casei and L. salivarius combination did not display any coaggregation with all strains. L. salivarius alone exhibited a stronger antagonistic effect on the tested organisms than L. casei alone or in combination. Based on the results, both probiotic strains showed good antimicrobial activities against oral pathogens and should be further studied for their human health benefits. [ABSTRACT FROM AUTHOR]

This study aimed to isolate and identify yeast species from kefir samples and to determine their probiotic characteristics in comparison with commercial probiotic yeast Saccharomyces boulardii. The microbial flora of traditional kefir samples were dominated by Saccharomyces cerevisiae and Kluyveromyces marxianus. Kefir isolates demonstrated higher auto‐aggregation, hydrophobicity and antioxidant properties compared to S. boulardii although S. boulardii demonstrated the highest survival rate under in␣vitro gastrointestinal digestion conditions followed by two kefir yeasts K. marxianus and Kazachstania unispora. Importantly, kefir isolates revealed strong antifungal activities against mould species except Penicillium roqueforti. These findings suggest probiotic and functional roles of yeast strains isolated from traditional kefir samples. [ABSTRACT FROM AUTHOR]

Background: Auto-aggregation is a desired property for probiotic strains because it is suggested to promote colonization of the human intestine, to prevent pathogen infections and to modulate the colonic mucosa. We recently reported the generation of adapted mutants of Lactiplantibacillus plantarum NZ3400, a derivative of the model strain WCFS1, for colonization under adult colonic conditions of PolyFermS continuous intestinal fermentation models. Here we describe and characterize the emerge of an auto-aggregating phenotype in L. plantarum NZ3400 derivatives recovered from the modelled gut microbiota. Results: L. plantarum isolates were recovered from reactor effluent of four different adult microbiota and from spontaneously formed reactor biofilms. Auto-aggregation was observed in L. plantarum recovered from all microbiota and at higher percentage when recovered from biofilm than from effluent. Further, auto-aggregation percentage increased over time of cultivation in the microbiota. Starvation of the gut microbiota by interrupting the inflow of nutritive medium enhanced auto-aggregation, suggesting a link to nutrient availability. Auto-aggregation was lost under standard cultivation conditions for lactobacilli in MRS medium. However, it was reestablished during growth on sucrose and maltose and in a medium that simulates the abiotic gut environment. Remarkably, none of these conditions resulted in an auto-aggregation phenotype in the wild type strain NZ3400 nor other non-aggregating L. plantarum, indicating that auto-aggregation depends on the strain history. Whole genome sequencing analysis did not reveal any mutation responsible for the auto-aggregation phenotype. Transcriptome analysis showed highly significant upregulation of LP_RS05225 (msa) at 4.1–4.4 log2-fold-change and LP_RS05230 (marR) at 4.5–5.4 log2-fold-change in all auto-aggregating strains compared to non-aggregating. These co-expressed genes encode a mannose-specific adhesin protein and transcriptional regulator, respectively. Mapping of the RNA-sequence reads to the promoter region of the msa-marR operon reveled a DNA inversion in this region that is predominant in auto-aggregating but not in non-aggregating strains. This strongly suggests a role of this inversion in the auto-aggregation phenotype. Conclusions: L. plantarum NZ3400 adapts to the in vitro colonic environment by developing an auto-aggregation phenotype. Similar aggregation phenotypes may promote gut colonization and efficacy of other probiotics and should be further investigated by using validated continuous models of gut fermentation such as PolyFermS. [ABSTRACT FROM AUTHOR]

The study aimed to evaluate the effect of thermal inactivation of potentially probiotic lactic acid bacteria (LAB) strains isolated from food on their ability to compete with pathogenic microorganisms. Five strains of LAB, previously isolated from food and characterized, one commercial reference strain of Lactiplantibacillus plantarum 299v, and two indicator strains of Staphylococcus aureus 25923 and Listeriamonocytogenes 15313 were used in the study. The experiment consisted in applying a stress factor (high temperature: 80 °C, at a different time: 5, 15, and 30 min) to the tested LAB cells to investigate the in vitro properties such as hydrophobicity abilities (against p-xylene and n-hexadecane), auto-aggregation, co-aggregation with pathogens, and inhibition of pathogens adhesion to the porcine gastric mucin. The bacterial strains showed various hydrophobicity to p-xylene (36–73%) and n-hexadecane (11–25%). The affinity for solvents expanded with increasing thermal inactivation time. All LAB isolates were able to auto-aggregate (ranging from 17 to 49%). Bacterial strains subjected to 5 and 15 min of thermal inactivation had the highest auto-aggregation ability in comparison to viable and heat-killed cells for 30 min. The LAB strains co-aggregated with pathogens to different degrees; among them, the highest scores of co-aggregation were observed for L. monocytogenes, reaching 27% (with 15 min of heat-killed LAB cells). All LAB strains reduced the adherence of pathogenic bacteria in the competition test, moreover, heat-killed cells (especially 15 min inactivated) were more efficient than viable cells. The properties of selected LAB strains as moderately heat-stressed forms analyzed in the study increased the prevention of colonization and elimination of pathogenic bacteria in the in vitro model of gastrointestinal tract. The thermal inactivation process may therefore preserve and modifies some characteristics of bacterial cells.

Recently, probiotic lactic acid bacteria have been utilized as therapeutic supplements and food additives. Nowadays, the interest has been increased regarding the commercial utilization of probiotic LAB strains isolated from traditional fermented food products. Therefore, the present study was aimed to investigate the probiotic properties of lactic acid bacteria isolated from traditional food sources viz. dosa batter and sauerkraut. Total 7 lactic acid bacteria were obtained, 4 from dosa batter and 3 from sauerkraut, out of which one isolate from each food source were selected based on their broadest antagonistic spectrum. These strains were identified using 16S r RNA technique as Lactobacillus plantarum DB-2 (isolated from dosa batter) and Lactobacillus plantarum SK-3 (isolated from sauerkraut). The investigation of acid-bile tolerance, antibiotic sensitivity, auto-aggregation, co-aggregation, bacterial adhesion to hydrocarbons were confirmed. The results revealed normal growth of L. plantarum DB-2 and L. plantarum SK-3 in the presence of low pH, high bile salt concentration and ability to produce antimicrobial compounds viz. bacteriocin and H2 O2 . No gelatinase, lipase and hemolytic activity were observed. Natural susceptibility to the tested antibiotics was investigated. Thus, according to these results, L. plantarum DB-2 and SK-3 proved the good probiotic candidates as they survived during stress conditions posing to them and can be exploited for the preparation of nutraceutical products. This study also revealed the potential of using LAB and /or bacteriocin produced by them as food bio preservative to control food borne pathogenic bacteria in near future.

Aim. The study of minimal ter operon as a determinant of tellurium resistance (TeR) is important for the purpose of confirming the relationship of these genes to the pathogenicity of microorganisms. The ter operon is widespread among bacterial species and pathogens, implicated also in phage inhibition, oxidative stress and colicin resistance. So far, there is no experimental evidence for the role of the Escherichia coli (E. coli) minimal ter operon in ultraviolet C (UVC) resistance, biofilm formation and auto-aggregation. To identify connection with UVC resistance of the minimal ter operon, matched pairs of Ter-positive and -negative E. coli cells were stressed and differences in survival and whole genome sequence analysis were performed. This study was aimed also to identify differences in phenotype of cells induced by environmental stress. Methods. In the current study, a minimal ter operon(terBCDEΔF) originating from the uropathogenic strain E. coli KL53 was used. Clonogenic assay was the method of choice to determine cell reproductive death after treatment with UVC irradiation at certain time intervals. Bacterial suspensions were irradiated with 254 nm UVC-light (germicidal lamp in biological safety cabinet) in vitro. UVC irradiance output was 2.5 mW/cm² (calculated at the UVC device aperture) and plate-lamp distance of 60 cm. DNA damage analysis was performed using shotgun sequencing on Illumina MiSeq platform. Biofilm formation was measured by a crystal violet retention assay. Auto-aggregation assay was performed according to the Ghane, Babaeekhou & Ketabi (2020). Results. A large fraction of Ter-positive E. coli cells survived treatment with 120-s UVC light (300 mJ/cm²) compared to matched Ter-negative cells; ~5-fold higher resistance of Ter-positive cells to UVC dose (p = 0.0007). Moreover, UVC surviving Ter-positive cells showed smaller mutation rate as Ter-negative cells. The study demonstrated that a 1200-s exposure to UVC (3,000 mJ/cm2) was sufficient for 100% inhibition of growth for all the Ter-positive and -negative E. coli cells. The Ter-positive strain exhibited of 26% higher auto-aggregation activities and was able to inhibit biofilm formation over than Ter-negative strain (**** P < 0.0001). Conclusion. Our study shows that Ter-positive cells display lower sensitivity to UVC radiation, corresponding to a presence in minimal ter operon. In addition, our study suggests that also auto-aggregation ability is related to minimal ter operon. The role of the minimal ter operon (terBCDEΔF) in resistance behavior of E. coli under environmental stress is evident. [ABSTRACT FROM AUTHOR]

We hypothesized that the initial events leading to biofilm formation by bacteria, in general, are predominantly mediated by cell surface physicochemical interactions, and that natural products can impact the process by altering cell surface physicochemical properties. We exemplified this phenomenon using Actinomyces naeslundii as the model organism, and using tea products to modify its cell surface physicochemical properties. To test the hypothesis, a non-linear multiple regression model incorporating a normal distribution curve was constructed to explain the impact of tea extracts on the physiochemical processes of biofilm formation by A. naeslundii. The model utilized tea extract-induced changes in cell surface physicochemical properties as independent variables, and the corresponding biofilm formation as a dependent variable. Five different tea extracts were used to treat A. naeslundii , and their impact on the cell surface hydrophobicity, charge, auto-aggregation, attachment and biofilm formation on four different hard surfaces were measured and the data were used to construct the model. The established model was then tested in independent experiments involving other plant extracts and purified phytochemicals. Experimental results showed that the tea extracts significantly reduced cell surface hydrophobicity (by up to 21.3%), increased cell surface charge and auto-aggregation (by up to 4.5 mV and 14.9%, respectively), inhibited attachment (by 0.6–2.5 log CFU cm−2) and affected biofilm formation (by up to 0.6 log CFU cm−2). The model indicated that both cell surface hydrophobicity and charge played an important role in bacterial auto-aggregation and attachment, and that the latter two phenomena significantly correlated with subsequent biofilm development. The accuracy of the model construct was approximately 64%. This modelling approach can be employed for other microbial colonization systems to predict biofilm formation, and to study the impact of cell surface physicochemical properties in biofilm development. [ABSTRACT FROM AUTHOR]

Postbiotics are functional bioactive substances manufactured during fermentation in a food matrix, which can be used to improve human health, but their influence on the adhesion potential and physicochemical cell surface of probiotics is still unclear. We examined the postbiotic influence produced by Escherichia coli Nissle 1917 in functional labneh on cell surface properties (auto-aggregation, hydrophobicity, and co-aggregation) and the adhesion capacities of three probiotic strains. The most commonly detected effects of probiotics, particularly Lsyn−7, were an increase in auto-aggregation, hydrophobicity, co-aggregation, and adhesion ability of the tested strains. Lactobacillus rhamnosus with Lsyn−7 (59%) presented the highest hydrophobicity, whereas the least adhesion to xylene was detected in L. rhamnosus with LHM. Lactobacillus casei with Lsyn−7 showed the highest auto-aggregation after 24 h (60.55%). Moreover, it also has a strong adhesion to Caco-2 cells and effectively prevents the binding of Salmonella Typhimurium to Caco-2 cells. Lactobacillus plantarum with Lsyn−7 presented the strongest co-aggregation with Staphylococcus aureus (85.1%), S. typhimurium (85. 02%) and Listeria monocytogenes (77.4%). The adherence potential of tested probiotic strains was highly correlated with auto-aggregation, hydrophobicity, co-aggregation, and competitive inhibition of L. monocytogenes and S. typhimurium. The findings suggest that Lsyn−7 can be a candidate to promote the adhesion potential of selected probiotic strains. For the reason that the application of probiotic strains has been more interested in their positive influences in the gastrointestinal tract, it is essential to use some functional compounds, such as postbiotics, to improve adhesion abilities and cell surface properties in terms of bacterial binding.

Objectives The screening of traditional fermented products is essential for the assessment of safety, security, and further development of functional foods for the well-being of human health. The aim of the present study was to isolate and identify bacteria from fermented raw milk samples that exhibit health benefits upon consumption. Methods In order to confirm the isolates as probiotics, several in vitro assays were conducted to assess the probiotic properties of isolated bacteria. The initial screening includes tolerance to acid, bile, pancreatin, and NaCl. The cell surface properties demonstrate their interaction with mucosal epithelium, which includes hydrophobicity and auto-aggregation assay. Safety assessment was done by performing haemolytic test and antibiotic susceptibility test. The antagonistic activity of probiotic strain was further evaluated against some pathogenic bacteria. Results Lactobacillus plantarum (L. plantarum) isolated from fermented raw milk was preliminarily identified by biochemical tests and further confirmed using 16S rRNA identification. The isolate designated as L. plantarum strain GCC_19M1 demonstrated significant tolerance to low pH, 0.3% bile, 0.5% pancreatin, and 5% NaCl. In the presence of simulated gastric juice (at pH 3), the isolate exhibited a survival rate of 93.48–96.97%. Furthermore, the development of ecological niches in the human gut and their successful accumulation have been revealed by auto-aggregation and hydrophobicity properties. Absence of haemolytic activity ensures the non-virulent nature of the strain. Lactobacillus plantarum strain GCC_19M1 showed susceptibility towards gentamicin, tetracycline, kanamycin, meropenem, and ceftriaxone and exhibited an antagonistic effect on pathogenic bacteria. Conclusion The obtained results conveyed that L. plantarum strain GCC_19M1 has strong probiotic potential, and its presence in the fermented raw milk products may serve as a potent functional probiotic food. [ABSTRACT FROM AUTHOR]

Human milk is a source of various lactic acid bacteria with the potential of probiotics. The aim of this study was to screen in vitro some probiotic properties of Lactobacillus gasseri MA-1 originated from human milk. The strain showed γ-hemolytic activity (no hemolytic activity) and susceptibility to Chloramphenicol, Cloxacillin and Penicillin G antibiotics. MA-1 with safety properties also exhibited a good tolerance to pH 2 and 0.3% bile conditions. L. gasseri MA-1 showed high ability of auto-aggregation (97%). The co-aggregation activities the strain with five human (Listeria monocytogenes ATCC 7644, Escherichia coli ATCC 35218, Salmonella enteritidis ATCC 13076, Escherichia coli O157:H7 and Salmonella enteritidis RSKK 171) and two fish (Streptococcus agalactiae and Vibrio alginolyticus) originated bacteria varied from 45% to 57%. The results indicated that, L. gasseri MA-1 strain could be a promising candidate for probiotic products. [ABSTRACT FROM AUTHOR]

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Gut bacterium Enterococcus mundtii is one of the predominant bacterial species in the larval gut of the diamondback moth, Plutella xylostella. Probiotic characterization in auto-aggregation and hydrophobicity, carbon use ability, and pH and osmotic environment adaptability of this bacterium were analyzed. Results exhibited that E. mundtii showed inhibition against Micrococcus luteus, Bacillus thuringiensis and Escherichia coli. It revealed a high auto-aggregation score and a hydrophilic cell surface. It metabolized 24.21% of the tested carbon sources with informative utilization patterns in organic acids and carbohydrates. It had a wide range of adaptabilities, and could still metabolize in osmolytes with up to 6% potassium chloride, 6% sodium chloride, 20% ethylene glycol, 5% sodium sulfate, 2% sodium lactate, 7% urea, 200 mM sodium phosphate (pH 7.0), 20 mM sodium benzoate (pH 5.2), 100 mM ammonium sulfate (pH 8.0), and 100 mM sodium nitrate; while it could not metabolize sodium lactate ranging from 3% to 12%, sodium formate ranging from 1% to 6%, or sodium nitrite ranging from 10 to 100 mM. Enterococcus mundtii exhibited active metabolism under pH values between 5 and 10, active deaminase activity but no decarboxylase activity. The probiotic characterization of E. mundtii increased our knowledge of adaptability in gut environments. [ABSTRACT FROM AUTHOR]

Foodborne spoilage bacteria may pose a serious risk to food quality by forming biofilms that adhere to food processing devices and food surfaces, thus causing cross-contamination and deterioration of food products. In order to effectively control microbial contamination, understanding the bacterial profiles related to biofilm formation in situ is crucial. Pseudomonas , Aeromonas , and Serratia are typically considered as prevalent spoilage organisms in chilled meat, which is particularly susceptible to deterioration during storage and transportation. In this study, four strains (Serratia liquefaciens F5, Aeromonas salmonicida H8, Pseudomonas saponiphila G7, and Aeromonas veronii G8) were cultured in situ in chilled chicken claws as the experimental group and in Tryptic Soy Broth (TSB) as the control group. The results showed that tested strains differed in ability to adhere, with S. liquefaciens F5 significantly exhibiting the highest biofilm formation capacity (P < 0.05). Moreover, it was discovered that higher protein and polysaccharides concentrations enhanced bacterial auto-aggregation and that the protein content of extracellular polymeric substances (EPS) positively correlated with bacterial surface hydrophobicity. On the 4th day, the protein content in EPS of each strain was significantly higher in vitro than in situ (P < 0.05). Furthermore, the rate of increase in auto-aggregation capacity and surface hydrophobicity proved faster in vitro than in situ for each strain due to higher polysaccharides and protein contents. The primary components (proteins, polysaccharides) in the EPS of the four strains increased as the biofilm formation process progressed, further confirmed by Attenuated Total Reflection Fourier Transform Infrared Spectroscopy (ATR-FTIR) spectra. Scanning electron microscopy revealed that A. salmonicida H8 can create biofilms on the surface of chicken claws, which severely disrupts the tissue structure of chilled meat. These observations will offer a theoretical foundation for a thorough investigation of the spoiling outcomes and adhesion characteristics of various meat-derived spoilage bacteria. • In situ , S. liquefaciens F5 had the strongest adhesion and spoilage capacity. • Lesser EPS produced by bacteria in situ compared to those in vitro. • The proteins and polysaccharides in EPS boost bacterial auto-aggregation. • Proteins and polysaccharides accelerated the process of biofilm formation. • Proteins in EPS increased the hydrophobicity of bacterial surfaces. [ABSTRACT FROM AUTHOR]

Clostridioides difficile (C. difficile) is responsible for one of the most common nosocomial infections worldwide. This work assessed associations between biofilm-formation capacity levels of C. difficile and cell viability, motility, flagella, motility and auto-aggregation in 118 clinical isolates. Biofilm production was assessed by the crystal violet method. Cell viability was determined by BacTiter-Glo™ Microbial Cell Viability Assay and live-imaging microscopy. Expression levels of LuxS, Cwp84 , Spo0A, PilA, and FliC were measured by real-time PCR. Motility was visually assessed in agar tubes. Auto-aggregation levels were determined by OD 600 measurements. Out of 118 isolates, 66 (56 %) were biofilm producers, with most being strong or moderate producers. Cell viability, motility and auto-aggregation positively correlated with biofilm-production capacity (p = 0.0001, p = 0.036 and p < 0.0001, respectively). Positive associations were found between pil A, fliC and lux S expression levels and biofilm-production capacity (p = 0.04, p = 0.01, p = 0.036, respectively). This is the first report of associations between biofilm-formation capacity and cell viability, pil A, fliC, and lux S gene expression, auto-aggregation and motility. These correlations should be further explored to expand knowledge on the regulation of C. difficile biofilm formation, and pathogenesis, which will have notable implications on treatment options. • Biofilm formation is a virulence factor of C. difficile. • We quantified the level of biofilm formation in 118 clinical C. difficile isolates. • We assessed factors that affect biofilm formation capacity. • Cell viability positively correlated with biofilm-production capacity. • Motility and auto-aggregation were associated with biofilm-production capacity. [ABSTRACT FROM AUTHOR]

Escherichia coli C is a strong biofilm producer in comparison to E. coli K-12 laboratory strains due to higher expression of the pgaABCD operon encoding the enzymes for the biosynthesis of the extracellular polysaccharide poly-β-1,6-N-acetylglucosamine (PNAG). The pgaABCD operon is negatively regulated at the post-transcriptional level by two factors, namely CsrA, a conserved RNA-binding protein controlling multiple pathways, and the RNA exonuclease polynucleotide phosphorylase (PNPase). In this work, we investigated the molecular bases of different PNAG production in C-1a and MG1655 strains taken as representative of E. coli C and K-12 strains, respectively. We found that pgaABCD operon expression is significantly lower in MG1655 than in C-1a; consistently, CsrA protein levels were much higher in MG1655. In contrast, we show that the negative effect exerted by PNPase on pgaABCD expression is much stronger in C-1a than in MG1655. The amount of CsrA and of the small RNAs CsrB, CsrC, and McaS sRNAs regulating CsrA activity is dramatically different in the two strains, whereas PNPase level is similar. Finally, the compensatory regulation acting between CsrB and CsrC in MG1655 does not occur in E. coli C. Our results suggest that PNPase preserves CsrA-dependent regulation by indirectly modulating csrA expression.

We isolated several strains of human and animal origin, focusing on the genera Lactobacillus and Bifidobacterium. Samples of cow colostrum, feces and saliva of calves and piglets, and infant feces were acquired, bacterial strains were isolated and identified, and twenty strains of lactobacilli and bifidobacteria were shortlisted for further in vitro analysis of adhesion capacity to human cells, surface hydrophobicity, and auto-aggregation. Adhesion capacity was evaluated using a mixture of Caco-2 and HT-29-MTX cells and hydrophobicity was measured using the microbial adhesion to the hydrocarbon method. Lactobacillus reuteri was the most frequently isolated species, followed by L. casei subsp. paracasei and L. gasseri; all strains were isolated from infant feces. Bifidobacteria were represented by the species B. longum (infant feces), and B. thermophilum and B. pseudolongum (calves, piglets). All twenty strains showed good adhesion capacities to the mixed cell culture (17.7-37.2%), particularly, L. reuteri isolates K7 and K14 (37.2% and 35.5%, respectively). In hydrophobicity and auto-aggregation assays, strain-specific differences irrespective of the origin or taxonomic group were observed. Hydrophobicity values varied considerably (from 6.1% to 87.4%), whereas auto-aggregation ability ranged from 21.7% to 69.7%. No relation was observed between hydrophobicity and adhesion capacity; instead, auto-aggregation was apparently related with adhesion. [ABSTRACT FROM AUTHOR]

Aim: Porphyromonas gingivalis and Prevotella intermedia are pathogenic bacteria that cause several periodontal diseases such as periodontitis. They frequently form biofilm to protect from threats such as antimicrobial agents. Hainosan (painongsan in Chinese) is a Japanese traditional kampo and traditional Chinese medicine formula used to treat acute and chronic purulent disease. The aim of the present study was to elucidate the mechanism of antibacterial effects such as anti‐biofilm activity, of hainosan extract (HNS) against Porphyromonas gingivalis and Prevotella intermedia. Methods: The antibacterial and anti‐biofilm activity of HNS was examined on bacterial turbidity and colony‐forming unit analysis, transmission electron microscopy, microplate analysis, and hydrophobicity and auto‐aggregation analysis. Results: HNS significantly suppressed the growth of Porphyromonas gingivalis and Prevotella intermedia. It also significantly inhibited the formation of biofilm from Porphyromonas gingivalis and Prevotella intermedia. The size and shape of HNS‐treated Porphyromonas gingivalis and Prevotella intermedia were significantly smaller and irregular. Furthermore, HNS reduced the bacterial auto aggregation and hydrophobicity of the bacterial cell surface. These antibacterial effects of HNS were greater than those of hangeshashinto, another Japanese traditional kampo medicine formula for oral cavity inflammation. Conclusion: HNS may be useful for the treatment of Porphyromonas gingivalis and Prevotella intermedia‐induced periodontitis because of the inhibition of bacterial biofilm formation. [ABSTRACT FROM AUTHOR]

Recently, probiotic lactic acid bacteria have been utilized as therapeutic supplements and food additives. Nowadays, the interest has been increased regarding the commercial utilization of probiotic LAB strains isolated from traditional fermented food products. Therefore, the present study was aimed to investigate the probiotic properties of lactic acid bacteria isolated from traditional food sources viz. dosa batter and sauerkraut. Total 7 lactic acid bacteria were obtained, 4 from dosa batter and 3 from sauerkraut, out of which one isolate from each food source were selected based on their broadest antagonistic spectrum. These strains were identified using 16S r RNA technique as Lactobacillus plantarum DB-2 (isolated from dosa batter) and Lactobacillus plantarum SK-3 (isolated from sauerkraut). The investigation of acid-bile tolerance, antibiotic sensitivity, auto-aggregation, co-aggregation, bacterial adhesion to hydrocarbons were confirmed. The results revealed normal growth of L. plantarum DB-2 and L. plantarum SK-3 in the presence of low pH, high bile salt concentration and ability to produce antimicrobial compounds viz. bacteriocin and H2O2. No gelatinase, lipase and hemolytic activity were observed. Natural susceptibility to the tested antibiotics was investigated. Thus, according to these results, L. plantarum DB-2 and SK-3 proved the good probiotic candidates as they survived during stress conditions posing to them and can be exploited for the preparation of nutraceutical products. This study also revealed the potential of using LAB and /or bacteriocin produced by them as food bio preservative to control food borne pathogenic bacteria in near future. [ABSTRACT FROM AUTHOR]

The study evaluated the safety and colonisation properties of four lactic acid bacteria (LAB), by determining their cell hydrophobicity and aggregation abilities. In addition, the presence of virulence and resistance genes was assayed in these probiotic candidates. Lactobacillus reuteri ZJ625, Lactobacillus reuteri VB4, Lactobacillus salivarius ZJ614 and Streptococcus salivarius NBRC13956 were tested for cell surface hydrophobicity abilities against xylene, chloroform and ethyl acetate. The isolates were also tested for auto-aggregation and co-aggregation abilities; the optical densities of cell growth were measured after 1, 2, 3 and 4 h of experimental set-up. DNA was extracted from all the four isolates and amplified using PCR with specific primers to detect virulence genes of adhesion collagen protein (ace) and aggregation substances (agg and asa); also, resistance genes of Vancomycin vanA, Vancomycin vanC1 and Vancomycin vanC2/3 were assayed in the four isolates. The isolates showed high hydrophobicity to all solvents: xylene (78–84%), chloroform (68–75%) and ethyl acetate (52–60%). High auto- and co-aggregations ranging from 60 to 70% and from 45 to 56% respectively were observed in the isolates after 4 h of incubation at 37 °C. Some of the tested isolates showed the presence of virulence and resistance genes; however, this does not indicate that these genes are unsafe because their transmission and expression abilities are unknown. Therefore, in this study, the isolates studied are considered safe for use as future probiotics, as revealed from results presented, which generally represents the scanned safety evaluations of the isolates as promising probiotics. [ABSTRACT FROM AUTHOR]

The study aimed to identify two lactic acid bacteria from human breast milk and evaluate for their probiotic potential. Lactobacillus fermentum strains showed various degree of antibiotic susceptibility profile to clinical commercial antibiotics. The MA-7 and MA-8 strains have never lost their vitality at pH 2 and 3. Lactobacillus fermentum MA-8 exhibited more resistance to 0.3 and 1% bile concentrations than MA-7 strain. Both of the L. fermentum strains can tolerate the simulated gastric and intestinal juices. The strains showed high auto-aggregation percentages varied from 95 to 98%. Both isolates also exhibited gamma hemolytic activity. The cholesterol lowering activity of MA-7 and MA-8 strains was varied from 34.84 to 91.15%. The supernatants showed higher anti-cholesterol activity compared to pellets. The results demonstrated that both L. fermentum strains maybe good probiotic candidates and may have potential as health biotherapeutic with cholesterol-lowering effects. [ABSTRACT FROM AUTHOR]

Four hundred strains isolated from Tunisian sheep and goat raw milks were initially screened for their ability to survive the GastroIntestinal Tract (GIT). Forty-three among the four hundred bacteria were resistant to pepsin, pH 2, pancreatin and bile salts at 0.3%, even after 5 hours of incubation. Identification using 16S rRNA gene sequencing was established and we obtained as a species Lactobacillus plantarum (29 isolates from sheep milk and 11 from goat milk) and Lactobacillus pentosus (2 isolates from sheep milk and 1 from goat milk). We showed the ability for auto-aggregation and/or hydrophobicity properties. Finally, both M63 and C78 strains showed an important level of adhesion to three intestinal epithelial cells Caco-2 TC7, HT29-MTX, and HT29-CL.16E. Taken together, these properties allow the lactobacilli strains to be considered promising beneficial strains for developing functional foods for consumers. [ABSTRACT FROM AUTHOR]

In this study, for the first time, we examined some of the physico-chemical properties of the cell surface of Akkermansia muciniphila DSM 22959, comparing it with those of Lactobacillus rhamnosus GG—one of the most extensively studied probiotic microorganisms. In particular, hydrophobicity, auto-aggregation, co-aggregation, and biofilm formation were investigated. In addition, antibiotic susceptibility, co-culture, and antimicrobial activity of the two strains were compared. Hydrophobicity was evaluated using xylene and toluene, showing that A. muciniphila DSM 22959 possessed moderate hydrophobicity. A. muciniphila showed a faster and higher auto-aggregation ability than Lb. rhamnosus GG, but a lower aptitude in biofilm formation. In the co-aggregation test, the best performance was obtained by Lb. rhamnosus GG. Regarding the susceptibility to antibiotics, the differences between the two strains were remarkable, with A. muciniphila DSM 22959 showing resistance to half of the antibiotic tested. Interesting results were also obtained with regard to the stimulating effect of Lb. rhamnosus GG on the growth of A. muciniphila when co-cultured.

Lipopolysaccharides, major molecules in the outer membrane of Gram-negative bacteria, play important roles on membrane integrity of the cell. However, how the core oligosaccharide of lipopolysaccharide affect the membrane behavior is not well understood. In this study, the relationship between the core oligosaccharide of lipopolysaccharide and the membrane behavior was investigated using a series of Escherichia coli mutants defective in genes to affect the biosynthesis of core oligosaccharide of lipopolysaccharide. Cell surface hydrophobicity, outer membrane permeability, biofilm formation and auto-aggregation of these mutant cells were compared. Compared to the wild type W3110, cell surface hydrophobicities of mutant ΔwaaC, ΔwaaF, ΔwaaG, ΔwaaO, ΔwaaP, ΔwaaY and ΔwaaB were enhanced, outer membrane permeabilities of ΔwaaC, ΔwaaF, ΔwaaG and ΔwaaP were significantly increased, abilities of biofilm formation by ΔwaaC, ΔwaaF, ΔwaaG, ΔwaaO, ΔwaaR, ΔwaaP, ΔwaaQ and ΔwaaY decreased, and auto-aggregation abilities of ΔwaaC, ΔwaaF, ΔwaaG, ΔwaaO, ΔwaaR, ΔwaaU, ΔwaaP and ΔwaaY were strongly enhanced. These results give new insight into the influence of core oligosaccharide of lipopolysaccharide on bacterial cell membrane behavior.

Abstract In this work, the probiotic or health-beneficial potential of 142 Saccharomyces strains isolated from food ecosystems belonging to the collection of the Yeast Biotechnology Laboratory (University of Castilla-La Mancha) have been studied. They were screened for their ability to resist and grow when exposed to simulated in vitro digestion conditions. As a result, 44 strains showed good kinetic properties and were chosen through k-means and one-way ANOVA and used to assess other important probiotic characteristics. For the second step, a Principal Component Analysis was run with the results from auto-aggregation and hydrophobicity at 30 °C assays, antibiotic resistance and antimicrobial activity, and 10 yeasts were then selected in order to study their biofilm formation capability, auto-aggregation and hydrophobicity at 37 °C, viability and biofilm formation after simulated sequential salivary-gastric-intestinal digestion. The most relevant results were those that showed the biofilm formation and hydrophobicity behaviour, so they were used for characterized the most promising probiotic candidates. The final results showed that the strains 132, 139 and 146 were the best ones. Highlights • The probiotic potential of 142 yeast strains isolated from food products and beverages was evaluated. • The selection was based on gastrointestinal resistance, auto-aggregation, hydrophobicity and biofilm formation capability. • 3 Saccharomyces yeasts showed promising probiotic properties. [ABSTRACT FROM AUTHOR]

Due to healthcare is increasing in nowadays, the use of the commercial probiotics is in progress and each day they are more demanded. The challenge of this study is to identify yeast species for using as probiotic organisms. Thus, the research applied a step-by-step approach, to study the probiotic potential of non- Saccharomyces yeast strains. The 215 yeasts were isolated from different environments such as wineries, oil mills, brines cheeses, fermented vegetables and distilleries in previous works and were identified to strain level by RAPD-PCR technique resulting 108 different strains. A general screening was carried out to know the probiotic capability of the yeasts, following the next steps: study of the ability to resist and grow of the yeasts when they exposed to simulated in vitro digestion conditions and influence of time, temperature, pH and the presence of enzymes on the kinetic growth parameters (lag phase (λ), generation time (G), maximum OD (OD max ) and the specific growth rate constant (μ max )). The results made possible the selection of the 23% of the strains and they were assayed for knowing their capability of self-aggregation and hydrophobicity. Biofilm formation capacity and viability after simulated sequential salivary-gastric-intestinal digestion were then studied for the 10 best strains. Statistical analyses were applied in each step to make the selection. The final results showed that two yeasts, H. osmophila and P. kudriavzevii, were the most promising strains. [ABSTRACT FROM AUTHOR]

Evaluation of eleven candidate probiotic Lactobacillus strains isolated from human milk showed that some of the strains were well endowed with desirable cell surface and attachment attributes. The cell surface properties (hydrophobicity, auto-aggregation, attachment to collagen and HT-29 monolayer) of probiotic Lactobacillus species of human milk origin were compared with reference probiotic/ non-probiotic species and pathogenic strains. The bacterial adhesion to hydrocarbons (BATH) was determined using three aliphatic (Chloroform, n-Hexane and n-Octane) and two aromatic (Toluene and Xylene) solvents. Maximum affinity of Lactobacillus strains towards chloroform and toluene indicated the presence of low electron acceptor/ acidic surface components on cell surface of most of the strains. The highest value of per cent hydrophobicity was recorded with chloroform in HM1 (L. casei) (97·10 ± 3·35%) and LGG (98·92 ± 1·24%). A moderate auto-aggregation attribute was observed in all of our Lactobacillus isolates. Only HM10, HM12 and HM13 exhibited comparatively enhanced precipitation rate after 7 h of incubation period. The adhesion potential to collagen matrix was highest in LGG (26·94 ± 5·83%), followed by HM1 (11·07 ± 3·54%) and HM9 (10·85 ± 1·74%) whereas, on HT-29 cells, HM8 (14·99 ± 3·61%), HM3 (13·73 ± 1·14%) and HM1 (11·21 ± 3·18%) could adhere effectively. In this manner, we noticed that although the cell surface properties and adhesion prospective of probiotic bacteria were strain dependent, five of our isolates viz. HM1, HM3, HM8, HM9 and HM10 exhibited promising cell surface properties, which could be further targeted as indigenous probiotic. [ABSTRACT FROM AUTHOR]

The ability of lactic acid bacteria to form multi-cellular aggregates via self-aggregation is regarded as an important mechanism for stress tolerance, adhesion, colonization and genetic material exchange. The novel aggLr gene encoding for the auto-aggregation promoting protein (AggLr) of Lactococcus raffinolactis BGTRK10-1 was cloned. Heterologous expression of AggLr enabled auto-aggregation, higher hydrophobicity and collagen and fibronectin binding of the carrier strains. Domain analysis and the type of aggregates formed by cells expressing AggLr confirmed that this aggregation factor belongs to the family of high molecular weight proteins that the authors propose to be called Snow-flake Forming Collagen Binding Aggregation Factors (SFCBAF). An additional feature of SFCBAF is that they are rich in threonine and lysine and are free of cysteine in all of the aggregation factors described so far. In contrast to previously discovered SFCBAF, the gene encoding for AggLr is located on the chromosome in the strain BGTRK10-1. [ABSTRACT FROM AUTHOR]

Acidity often prevents the undesirable microbial colonization both in fermented foods and under gastric conditions. Thus, the acid resistance of Lactobacillus pentosus strains used as starter cultures and/or probiotics requires further understanding. This was investigated by means of comparative proteomic approach using three strains representing the phenotypes: resistant (AP2-15), intermediate (AP2-18) and sensitive (LP-1) to acidic conditions. Proteomic analysis of constitutive phenotypes revealed that the intrinsic resistance of L. pentosus is associated with the over-production of three principal proteins: 2,3-bisphosphoglycerate-dependent phosphoglycerate mutase 2 (PGAM-d), elongation factor G and 50S ribosomal protein L10, and additionally on ATP synthase subunit beta and chaperone protein DnaK; they are associated with metabolic pathways of proteins and carbohydrates, energy production and stress responses. Suggested protein biomarkers for acid resistance in L. pentosus include elongation factor G and PGAM-d, both being abundantly found in the constitutive proteome of the resistant phenotype under standard and acidic conditions. Furthermore, L. pentosus strains pre-exposed to acids displayed enhanced probiotic function such as auto-aggregation ability via surface proteins. We conclude that pre-exposure of probiotic L. pentosus strains to acid may strategically enhance their performance as starter cultures and probiotics. [ABSTRACT FROM AUTHOR]

The present study is focused on probiotic characterization of four yeasts viz. Pichia barkeri VIT-SJSN01, Yarrowia lipolytica VIT-ASN04, Wickerhamomyces anomalus VIT-ASN01 and Saccharomyces cerevisiae VIT-ASN03 isolated from food samples based on their auto-aggregation, co-aggregation ability and haemolytic activity. All the yeast strains showed good self-adhering and co-adhering potentiality with a value index of greater than 85%. None of the strains exhibited haemolysis which confirmed their non-pathogenic nature. Yeast strains were encapsulated in sodium alginate, sodium alginate coated with chitosan and sodium alginate-gelatinized with starch. Size and morphology of the beads and capsules were determined using SEM analysis. Encapsulation output and viability under storage condition was investigated. It was found that probiotic yeasts encapsulated in sodium alginate beads, chitosan coated beads and microcapsules showed better survival to simulated gastrointestinal conditions compared to free cells. [ABSTRACT FROM AUTHOR]

Enterobacter sp. strain FL was newly isolated from activated sludge and exhibited significant capability of auto-aggregation as well as aerobic denitrification. The removal efficiencies of NO3−-N, total nitrogen (TN), and TOC by strain FL in batch culture reached 94.6, 63.9, and 72.5% in 24 h, respectively. The production of N2O and N2 in the presence of oxygen demonstrated the occurrence of aerobic denitrification. The auto-aggregation index of strain FL reached 54.3%, suggesting a high tendency that the cells would agglomerate into aggregates. The production of extracellular polymeric substances (EPSs), which were mainly composed of proteins followed by polysaccharides, was considered to be related to the cell aggregation according to Fourier transform infrared (FT-IR) and confocal laser scanning microscopy (CLSM). The proteins in EPS were evenly and tightly combined to cells and altered the protein secondary structures of cell surface from random coils to β-sheets and three-turn helices. The alteration of protein secondary structures of cell surface caused by the proteins in EPS might play a dominant role in the auto-aggregation of strain FL. To further assess the feasibility of strain FL for synthetic wastewater treatment, a sequencing batch reactor (SBR), solely inoculated with strain FL, was conducted. During the 16 running cycles, the removal efficiency of NO3−-N was 90.2–99.7% and the auto-aggregation index was stabilized at 35.0–41.5%. The EPS promoted the biomass of strain FL to aggregate in the SBR. [ABSTRACT FROM AUTHOR]

The understanding of mechanisms of interactions between various bacterial cell surface proteins and host receptors has become imperative for the study of the health promoting features of probiotic enterococci. This study, for the first time, describes a novel enterococcal aggregation protein, AggE, from Enterococcus faecium BGGO9-28, selected from a laboratory collection of enterococcal isolates with auto-aggregation phenotypes. Among them, En. faecium BGGO9-28 showed the strongest auto-aggregation, adhesion to components of ECM and biofilm formation. Novel aggregation promoting factor AggE, a protein of 178.1 kDa, belongs to the collagen-binding superfamily of proteins and shares similar architecture with previously discovered aggregation factors from lactic acid bacteria (LAB). Its expression in heterologous enterococcal and lactococcal hosts demonstrates that the aggE gene is sufficient for cell aggregation. The derivatives carrying aggE exhibited the ten times higher adhesion ability to collagen and fibronectin, possess about two times higher adhesion to mucin and contribute to the increase of biofilm formation, comparing to the control strains. Analysis for the presence of virulence factors (cytolysin and gelatinase production), antibiotic resistance (antibiotic susceptibility) and genes (cylA, agg, gelE, esp, hylN, ace, efaAfs, and efaAfm) showed that BGGO9-28 was sensitive to all tested antibiotics, without hemolytic or gelatinase activity. This strain does not carry any of the tested genes encoding for known virulence factors. Results showed that BGGO9-28 was resistant to low pH and high concentrations of bile salts. Also, it adhered strongly to the Caco-2 human epithelial cell line. In conclusion, the results of this study indicate that the presence of AggE protein on the cell surface in enterococci is a desirable probiotic feature.

The understanding of mechanisms of interactions between various bacterial cell surface proteins and host receptors has become imperative for the study of the health promoting features of probiotic enterococci. This study, for the first time, describes a novel enterococcal aggregation protein, AggE, from Enterococcus faecium BGGO9-28, selected from a laboratory collection of enterococcal isolates with auto-aggregation phenotypes. Among them, En. faecium BGGO9-28 showed the strongest auto-aggregation, adhesion to components of ECM and biofilm formation. Novel aggregation promoting factor AggE, a protein of 178.1 kDa, belongs to the collagen-binding superfamily of proteins and shares similar architecture with previously discovered aggregation factors from lactic acid bacteria (LAB). Its expression in heterologous enterococcal and lactococcal hosts demonstrates that the aggE gene is sufficient for cell aggregation. The derivatives carrying aggE exhibited the ten times higher adhesion ability to collagen and fibronectin, possess about two times higher adhesion to mucin and contribute to the increase of biofilm formation, comparing to the control strains. Analysis for the presence of virulence factors (cytolysin and gelatinase production), antibiotic resistance (antibiotic susceptibility) and genes (cylA, agg, gelE, esp, hylN, ace, efaAfs, and efaAfm) showed that BGGO9-28 was sensitive to all tested antibiotics, without hemolytic or gelatinase activity. This strain does not carry any of the tested genes encoding for known virulence factors. Results showed that BGGO9-28 was resistant to low pH and high concentrations of bile salts. Also, it adhered strongly to the Caco-2 human epithelial cell line. In conclusion, the results of this study indicate that the presence of AggE protein on the cell surface in enterococci is a desirable probiotic feature. [ABSTRACT FROM AUTHOR]