Comparative genome-based identification of a cell wall-anchored protein from Lactobacillus plantarum increases adhesion of Lactococcus lactis to human epithelial cells

Lactiplantibacillus plantarum LM1001 Improves Digestibility of Branched-Chain Amino Acids in Whey Proteins and Promotes Myogenesis in C2C12 Myotubes

Lactiplantibacillus plantarum is a valuable potential probiotic species with various proven health-beneficial effects. L. plantarum LM1001 strain was selected among ten strains of L. plantarum based on proteolytic activity on whey proteins. L. plantarum LM1001 produced higher concentrations of total free amino acids and branched-chain amino acids (Ile, Leu, and Val) than other L. plantarum strains. Treatment of C2C12 myotubes with whey protein culture supernatant (1%, 2% and 3%, v/v) using L. plantarum LM1001 significantly increased the expression of myogenic regulatory factors, such as Myf-5, MyoD, and myogenin, reflecting the promotion of myotubes formation (p<0.05). L. plantarum LM1001 displayed β-galactosidase activity but did not produce harmful β-glucuronidase. Thus, the intake of whey protein together with L. plantarum LM1001 has the potential to aid protein digestion and utilization.

Genome Sequencing Unveils Nomadic Traits of Lactiplantibacillus plantarum in Japanese Post-Fermented Tea

Post-fermented tea production involving microbial fermentation is limited to a few regions, such as Southeast Asia and Japan, with Japan's Shikoku island being particularly prominent. Lactiplantibacillus plantarum was the dominant species found in tea leaves after anaerobic fermentation of Awa-bancha in Miyoshi City, Tokushima, and Ishizuchi-kurocha in Ehime. Although the draft genome of L. plantarum from Japanese post-fermented tea has been previously reported, its genetic diversity requires further exploration. In this study, whole-genome sequencing was conducted on four L. plantarum strains isolated from Japanese post-fermented tea using nanopore sequencing. These isolates were then compared with other sources to examine their genetic diversity revealing that L. plantarum isolated from Japanese post-fermented tea contained several highly variable gene regions associated with sugar metabolism and transportation. However, no source-specific genes or clusters were identified within accessory or core gene regions. This study indicates that L. plantarum possesses high genetic diversity and that the unique environment of Japanese post-fermented tea does not appear to exert selective pressure on L. plantarum growth.

Probiotic and Safety Evaluation of Twelve Lactic Acid Bacteria as Future Probiotics

The human gut flora is highly diverse. Most lactic acid bacteria (LAB) are widely used as probiotics in human and animal husbandry and have a variety of physiological benefits. This article mainly studied the bacteriostatic ability of LAB against four pathogenic bacteria, gastrointestinal environment tolerance, and adhesion ability to Caco-2 cells. The genome of Lactiplantibacillus plantarum L461 was sequenced and analyzed. The results showed that strains F512, L461, and D469 had the most significant inhibitory effects on Escherichia coli, Salmonella enterica B, Staphylococcus aureus, and Listeria monocytogenes. In addition, strains L461, C502, and P231 showed good tolerance after exposure to simulated gastric fluid for 0-4 h. Strains C502, H781, and L461 showed good tolerance in simulated intestinal fluid. Strains L461 and H781 showed good adhesion to Caco-2 cells. The number of viable bacteria was more than 60. Therefore, we screened L. plantarum L461 from 12 LAB strains through three aspects of evaluation, and conducted whole genome sequencing and analysis. Sequencing results showed that L. plantarum L461 had more defense mechanisms and phage annotation genes than L. plantarum WCFS1. Virulence factor studies showed that L. plantarum L461 has iron absorption system and adhesion-related gene annotation, indicating that L. plantarum L461 has survival advantage in intestinal tract. The predicted results showed that there were eight phages with phage resistance in L. plantarum L461. L. plantarum L461 is sensitive to several antibiotics, notably penicillin and oxacillin. In summary, the results of this study prove that L. plantarum L461 has good prebiotic function and is safe. Therefore, L. plantarum L461 can be safely used as a potential functional probiotic.

Draft genome sequence and probiotic functional property analysis of Lactobacillus gasseri LM1065 for food industry applications

Probiotics are defined as live organisms in the host that contribute to health benefits. Lactobacillus gasseri LM1065, isolated from human breast milk, was investigated for its probiotic properties based on its genome. Draft genome map and de novo assembly were performed using the PacBio RS II system and hierarchical genome assembly process (HGAP). Probiotic properties were determined by the resistance to gastric conditions, adherence ability, enzyme production, safety assessment and mobile genetic elements. The fungistatic effect and inhibition of hyphae transition were studied using the cell-free supernatant (CFS). L. gasseri LM1065 showed high gastric pepsin tolerance and mild tolerance to bile salts. Auto-aggregation and hydrophobicity were measured to be 61.21% and 61.55%, respectively. The adherence to the human intestinal epithelial cells was measured to be 2.02%. Antibiotic-resistance genes and putative virulence genes were not predicted in the genomic analysis, and antibiotic susceptibility was satisfied by the criteria of the European Food Safety Authority. CFS showed a fungistatic effect and suppressed the tricarboxylic acid cycle in Candida albicans (29.02%). CFS also inhibited the transition to true hyphae and damaged the blastoconidia. This study demonstrates the essential properties of this novel probiotic, L. gasseri LM1065, and potential to inhibit vaginal C. albicans infection.

Complete genome sequences of Lacticaseibacillus paracasei INIA P272 (CECT 8315) and Lacticaseibacillus rhamnosus INIA P344 (CECT 8316) isolated from breast-fed infants reveal probiotic determinants

Lacticaseibacillus paracasei INIA P272 and Lacticaseibacillus rhamnosus INIA P344, isolated from breast-fed infants, are two promising bacterial strains for their use in functional foods according to their demonstrated probiotic and technological characteristics. To better understand their probiotic characteristics and evaluate their safety, here we report the draft genome sequences of both strains as well as the analysis of their genetical content. The draft genomes of L. paracasei INIA P272 and L. rhamnosus INIA P344 comprise 3.01 and 3.26 Mb, a total of 2994 and 3166 genes and a GC content of 46.27 % and 46.56 %, respectively. Genomic safety was assessed following the EFSA guidelines: the identification of both strains was confirmed through Average Nucleotide Identity, and the absence of virulence, pathogenic and antibiotic resistance genes was demonstrated. The genome stability analysis revealed the presence of plasmids and phage regions in both genomes, however, CRISPR sequences and other mechanisms to fight against phage infections were encoded. The probiotic abilities of both strains were supported by the presence of genes for the synthesis of SCFA, genes involved in resistance to acid and bile salts or a thiamine production cluster. Moreover, the encoded exopolysaccharide biosynthesis genes could provide additional protection against the deleterious gastrointestinal conditions, besides which, playing a key role in adherence and coaggregation of pathogenic bacteria together with the high number of adhesion proteins and domains encoded by both genomes. Additionally, the bacteriocin cluster genes found in both strains, could provide an advantageous ability to compete against pathogenic bacteria. This genomic study supports the probiotic characteristics described previously for these two strains and satisfies the safety requirements to be used in food products.

Genes encoding bile salt hydrolase differentially affect adhesion of Lactiplantibacillus plantarum AR113

BACKGROUND

Adhesion is considered important for Lactiplantibacillus to persist in the human gut and for it to exert probiotic effects. Lactiplantibacillus plantarum contains a considerable number and variety of genes encoding bile salt hydrolases (bsh), but their effects on microbial adhesion remain poorly understood. To clarify the effects of four bsh on adhesion, we tried to knock out bsh (Δbsh) of L. plantarum AR113 using the CRISPR-Cas9 method, and compared the growth, auto-aggregation (R_AA ), co-aggregation (R_CA ), surface hydrophobicity (A_HC ) of AR113 wild-type and Δbsh strains and their adhesion abilities to HT29 cells.

RESULTS

We first obtained the AR113 Δbsh1,3,2,4 strain with four bsh knocked out. Their growth was significantly slower than the wild-type strain cultured in De Man, Rogosa, and Sharpe medium (MRS) with 3.0 g L^-1 glyco- or tauro-conjugated bile acid. Bsh had no significant effect on the growth of ten strains cultured in MRS, but Δbsh1 inhibited their growth when cultured in MRS containing 3.0 g L^-1 sodium glycocholate, whereas Δbsh4 instead promoted their growth in MRS with 3.0 g L^-1 sodium glycocholate and sodium taurocholate. R_CA and R_AA were linearly positive for all strains except AR113 Δbsh2,4, and A_HC and R_AA were negatively correlated for most strains excluding AR113 Δbsh2, with R_AA  = 6.38-25.05%, R_CA  = 5.17-9.22%, and A_CH  = 3.22-47.71%. The adhesion ability of ten strains cultured in MRS was higher than that of strains cultured in MRS with 3.0 g L^-1 bovine bile, and it was related to bsh2.

CONCLUSION

Bsh differentially affected the adhesion of AR113 series strains. This adds to the available information about substrate-gene-performance, and provides new information to enable engineering to regulate the colonization of Lactiplantibacillus. © 2021 Society of Chemical Industry.

Decoding the Gene Variants of Two Native Probiotic Lactiplantibacillus plantarum Strains through Whole-Genome Resequencing: Insights into Bacterial Adaptability to Stressors and Antimicrobial Strength

In this study, whole-genome resequencing of two native probiotic Lactiplantibacillus plantarum strains—UTNGt21A and UTNGt2—was assessed in order to identify variants and perform annotation of genes involved in bacterial adaptability to different stressors, as well as their antimicrobial strength. A total of 21,906 single-nucleotide polymorphisms (SNPs) were detected in UTNGt21A, while 17,610 were disclosed in the UTNGt2 genome. The comparative genomic analysis revealed a greater number of deletions, transversions, and transitions within the UTNGt21A genome, while a small difference in the number of insertions was detected between the strains. A divergent number of types of variant annotations were detected in both strains, and categorized in terms of low, moderate, and high modifier impact on the protein effectiveness. Although both native strains shared common specific genes involved in the stress response to the gastrointestinal environment, which may qualify as a putative probiotic (bile salt, acid, temperature, osmotic stress), they were different in their antimicrobial gene cluster organization, with UTNGt21A displaying a complex bacteriocin gene arrangement and dissimilar gene variants that might alter their defense mechanisms and overall inhibitory capacity. The genome comparison revealed 34 and 9 genomic islands (GIs) in the UTNGt21A and UTNGt2 genomes, respectively, with the overrepresentation of genes involved in defense mechanisms and carbohydrate utilization. In addition, pan-genome analysis disclosed the presence of various strain-specific genes (shell genes), suggesting a high genome variation between strains. This genome analysis illustrates that the bacteriocin signature and gene variants reflect a niche-inherent pattern. These extensive genomic datasets will guide us to understand the potential benefits of the native strains and their utility in the food or pharmaceutical sectors.

Lactococcus lactis, an Attractive Cell Factory for the Expression of Functional Membrane Proteins

Membrane proteins play key roles in most crucial cellular processes, ranging from cell-to-cell communication to signaling processes. Despite recent improvements, the expression of functionally folded membrane proteins in sufficient amounts for functional and structural characterization remains a challenge. Indeed, it is still difficult to predict whether a protein can be overproduced in a functional state in some expression system(s), though studies of high-throughput screens have been published in recent years. Prokaryotic expression systems present several advantages over eukaryotic ones. Among them, Lactococcus lactis (L. lactis) has emerged in the last two decades as a good alternative expression system to E. coli. The purpose of this chapter is to describe L. lactis and its tightly inducible system, NICE, for the effective expression of membrane proteins from both prokaryotic and eukaryotic origins.

Probiotic Properties of Bifidobacterium longum KABP042 and Pediococcus pentosaceus KABP041 Show Potential to Counteract Functional Gastrointestinal Disorders in an Observational Pilot Trial in Infants

Functional gastrointestinal disorders (FGIDs) are a common concern during the first year of life. Recognized as gut-brain axis disorders by Rome IV criteria, FGIDs etiology is linked to altered gut-brain interaction, intestinal physiology, and microbiota. In this regard, probiotics have emerged as a promising therapy for infant FGIDs. In this study, we have investigated the probiotic potential of the strains Bifidobacterium longum KABP042 and Pediococcus pentosaceus KABP041-isolated from healthy children's feces-in the treatment of FGIDs. To this scope, genome sequences of both strains were obtained and subjected to in silico analyses. No virulence factors were detected for any strain and only the non-transferable erm(49) gene, which confers resistance to erythromycin and clindamycin, was identified in the genome of B. longum KABP042. Safety of both strains was confirmed by acute oral toxicity in rats. In vitro characterization revealed that the strains tolerate gastric and bile challenges and display a great adhesion capacity to human intestinal cells. The two strains mediate adhesion by different mechanisms and, when combined, synergically induce the expression of Caco-2 tight junction proteins. Moreover, growth inhibition experiments demonstrated the ability of the two strains alone and in combination to antagonize diverse Gram-negative and Gram-positive bacterial pathogens during sessile and planktonic growth. Pathogens' inhibition was mostly mediated by the production of organic acids, but neutralization experiments strongly suggested the presence of additional antimicrobial compounds in probiotic culture supernatants such as the bacteriocin Lantibiotic B, whose gene was detected in the genome of B. longum KABP042. Finally, an exploratory, observational, pilot study involving 36 infants diagnosed with at least one FGID (infant colic and/or functional constipation) showed the probiotic formula was well tolerated and FGID severity was significantly reduced after 14 days of treatment with the 2 strains. Overall, this work provides evidence of the probiotic and synergic properties of strains B. longum KABP042 and P. pentosaceus KABP041, and of their potential to treat pediatric FGIDs. Clinical Trial Registration: [www.ClinicalTrials.gov], [identifier NCT04944628].

The Edible Plant Microbiome represents a diverse genetic reservoir with functional potential in the human host

Plant microbiomes have been extensively studied for their agricultural relevance on growth promotion and pathogenesis, but little is known about their role as part of the diet when fresh fruits and vegetables are consumed raw. Most studies describing these communities are based on 16S rRNA gene amplicon surveys, limiting our understanding of the taxonomic resolution at the species level and functional capabilities. In this study, we characterized microbes colonizing tomatoes, spinach, brined olives, and dried figs using shotgun metagenomics. We recovered metagenome-assembled genomes of novel lactic acid bacteria from green olives and identified high intra- and inter-specific diversity of Pseudomonas in tomatoes. All samples were colonized by Pseudomonas, consistent with other reports with distinct community structure. Functional characterization showed the presence of enzymes involved in vitamin and short chain fatty acid metabolism and degradation of diverse carbohydrate substrates including plant fibers. The dominant bacterial members were isolated, sequenced, and mapped to its metagenome confirming their identity and indicating the microbiota is culturable. Our results reveal high genetic diversity, previously uncultured genera, and specific functions reflecting a likely plant host association. This study highlights the potential that plant microbes can play when consumed as part of our diet and proposes these as transient contributors to the gut microbiome.

Recent advances in the concept of paraprobiotics: Nutraceutical/functional properties for promoting children health

Probiotics consumption has been associated with various health promoting benefits, including disease prevention and even treatment by modulating gut microbiota. Contrary to this, probiotics may also overstimulate the immune system, trigger systemic infections, harmful metabolic activities, and promote gene transfer. In children, the fragile immune system and impaired intestinal barrier may boost the occurrence of adverse effects following probiotics' consumption. To overcome these health challenges, the key focus has been shifted toward non-viable probiotics, also called paraprobiotics. Cell wall polysaccharides, peptidoglycans, surface proteins and teichoic acid present on cell's surface are involved in the interaction of paraprobiotics with the host, ultimately providing health benefits. Among other benefits, paraprobiotics possess the ability to regulate innate and adaptive immunity, exert anti-adhesion, anti-biofilm, anti-hypertensive, anti-inflammatory, antioxidant, anti-proliferative, and antagonistic effects against pathogens, while also enhance clinical impact and general safety when administered in children in comparison to probiotics. Clinical evidence have underlined the paraprobiotics impact in children and young infants against atopic dermatitis, respiratory and gastrointestinal infections, in addition to be useful for immunocompromised individuals. Therefore, this review focuses on probiotics-related issues in children's health and also discusses the Lactobacillus and Bifidobacterium spp. qualities for qualifying as paraprobiotics and their role in promoting the children's health.

Lactiplantibacillus plantarum strains isolated from spontaneously fermented cocoa exhibit potential probiotic properties against Gardnerella vaginalis and Neisseria gonorrhoeae

Background

Probiotics are important tools in therapies against vaginal infections and can assist traditional antibiotic therapies in restoring healthy microbiota. Recent research has shown that microorganisms belonging to the genus Lactobacillus have probiotic potential. Thus, this study evaluated the potential in vitro probiotic properties of three strains of Lactiplantibacillus plantarum, isolated during the fermentation of high-quality cocoa, against Gardnerella vaginalis and Neisseria gonorrhoeae. Strains were evaluated for their physiological, safety, and antimicrobial characteristics.

Results

The hydrophobicity of L. plantarum strains varied from 26.67 to 91.67%, and their autoaggregation varied from 18.10 to 30.64%. The co-aggregation of L. plantarum strains with G. vaginalis ranged from 14.73 to 16.31%, and from 29.14 to 45.76% with N. gonorrhoeae. All L. plantarum strains could moderately or strongly produce biofilms. L. plantarum strains did not show haemolytic activity and were generally sensitive to the tested antimicrobials. All lactobacillus strains were tolerant to heat and pH resistance tests. All three strains of L. plantarum showed antimicrobial activity against the tested pathogens. The coincubation of L. plantarum strains with pathogens showed that the culture pH remained below 4.5 after 24 h. All cell-free culture supernatants (CFCS) demonstrated activity against the two pathogens tested, and all L. plantarum strains produced hydrogen peroxide. CFCS characterisation in conjunction with gas chromatography revealed that organic acids, especially lactic acid, were responsible for the antimicrobial activity against the pathogens evaluated.

Conclusion

The three strains of L. plantarum presented significant probiotic characteristics against the two pathogens of clinical importance. In vitro screening identified strong probiotic candidates for in vivo studies for the treatment of vaginal infections.

Antimicrobial and anti-biofilm effects of probiotic Lactobacillus plantarum KU200656 isolated from kimchi

The probiotic properties and anti-pathogenic effects of Lactobacillus plantarum KU200656 (KU200656) isolated from Korean fermented kimchi against Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Salmonella Typhimurium were investigated. KU200656 showed high tolerance to artificial gastric acid (99.48%) and bile salts (102.40%) and this strain was safe according to antibiotic sensitivity test; it could not produce harmful enzymes, including β-glucuronidase. KU200656 exhibited high adhesion (4.45%) to intestinal cells, HT-29 cells, with high cell surface hydrophobicity (87.31% for xylene and 81.11% for toluene). Moreover, KU200656 co-aggregated with pathogenic bacteria and exhibited antibacterial activity and anti-adhesion properties against pathogens. The cell-free supernatant (CFS) of KU200656 inhibited biofilm formation by pathogenic bacteria. In addition, half of the minimum inhibitory concentration of the KU200656 CFS downregulated the expression of biofilm-related genes, as determined by quantitative real-time PCR. Therefore, KU200656 was demonstrated to possess anti-pathogenic effects and have potential for use as probiotics in the food industry.

Paraprobiotics and Postbiotics of Probiotic Lactobacilli, Their Positive Effects on the Host and Action Mechanisms: A Review

Lactobacilli comprise an important group of probiotics for both human and animals. The emerging concern regarding safety problems associated with live microbial cells is enhancing the interest in using cell components and metabolites derived from probiotic strains. Here, we define cell structural components and metabolites of probiotic bacteria as paraprobiotics and postbiotics, respectively. Paraprobiotics and postbiotics produced from Lactobacilli consist of a wide range of molecules including peptidoglycans, surface proteins, cell wall polysaccharides, secreted proteins, bacteriocins, and organic acids, which mediate positive effect on the host, such as immunomodulatory, anti-tumor, antimicrobial, and barrier-preservation effects. In this review, we systematically summarize the paraprobiotics and postbiotics derived from Lactobacilli and their beneficial functions. We also discuss the mechanisms underlying their beneficial effects on the host, and their interaction with the host cells. This review may boost our understanding on the benefits and molecular mechanisms associated with paraprobiotics and probiotics from Lactobacilli, which may promote their applications in humans and animals.

Screening, Safety Evaluation, and Mechanism of Two Lactobacillus fermentum Strains in Reducing the Translocation of Staphylococcus aureus in the Caco-2 Monolayer Model

Staphylococcus aureus is a common commensal of humans, and its translocation from gastrointestine to peripheral organs and tissues could cause severe diseases and complications. This study focuses on the screening and characterization of Lactobacillus strains with significant inhibitory effect on the translocation of S. aureus through Caco-2 monolayers. First, strains with strong affinity for mucin and Caco-2 cells were obtained, via microtiter plate assay and adhesion assay, respectively. Obtained bacteria were further tested for their inhibitory effects on the growth of S. aureus by well diffusion assay. Subsequently, two strains preincubated with Caco-2 monolayers were found to inhibit the translocation of S. aureus CMCC26003 by 80.95 and 43.96%, respectively, via the transcellular translocation assay. These two strains were then identified to be Lactobacillus fermentum NCU3087 and L. fermentum NCU3088. Second, the mechanism of inhibition was investigated by analyzing the relative concentration of tight junction proteins and proinflammatory cytokines of Caco-2 cells, by Western blot and enzyme-linked immunosorbent assay, respectively. Results showed that both NCU3087 and NCU3088 significantly attenuated the degradation of occludin, claudin-1, ZO-1, and JAM-1 and suppressed the secretion of interleukin 6 and tumor necrosis factor-α induced by S. aureus, to different extent. Moreover, two Lactobacillus strains could barely translocate the Caco-2 monolayers, had no hemolytic activity, displayed strong resistance to gastrointestinal fluids, and were sensitive or moderate sensitive to nine clinically relevant antibiotics. Collectively, this study identified two Lactobacillus strains with significant inhibitory effect on the translocation of S. aureus, and their safeness for application was evaluated, thereby providing potential solutions for prevention of S. aureus and prophylaxis of related diseases.

Adhesion mechanisms mediated by probiotics and prebiotics and their potential impact on human health

Adhesion ability to the host is a classical selection criterion for potential probiotic bacteria that could result in a transient colonisation that would help to promote immunomodulatory effects, as well as stimulate gut barrier and metabolic functions. In addition, probiotic bacteria have a potential protective role against enteropathogens through different mechanisms including production of antimicrobial compounds, reduction of pathogenic bacterial adhesion and competition for host cell binding sites. The competitive exclusion by probiotic bacteria has a beneficial effect not only on the gut but also in the urogenital tract and oral cavity. On the other hand, prebiotics may also act as barriers to pathogens and toxins by preventing their adhesion to epithelial receptors. In vitro studies with different intestinal cell lines have been widely used along the last decades to assess the adherence ability of probiotic bacteria and pathogen antagonism. However, extrapolation of these results to in vivo conditions still remains unclear, leading to the need of optimisation of more complex in vitro approaches that include interaction with the resident microbiota to address the current limitations. The aim of this mini review is to provide a comprehensive overview on the potential effect of the adhesive properties of probiotics and prebiotics on the host by focusing on the most recent findings related with adhesion and immunomodulatory and antipathogenic effect on human health.

A Surface Protein From Lactobacillus plantarum Increases the Adhesion of Lactobacillus Strains to Human Epithelial Cells

Adhesion to epithelial cells is considered important for Lactobacillus to exert probiotic effects. In this study, we found that trypsin treatment decreased the adhesion ability of Lactobacillus plantarum AR326 and AR269, which exhibit good adhesion ability, and surface proteins extracts increased the adhesion of the strains with poor adhesion ability. By SDS–polyacrylamide gel electrophoresis and mass spectrometry analysis, the main component of the surface proteins was detected and identified as a protein of approximately 37 kDa. It was 100% homologous with glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from L. plantarum WCFS1. The adhesion of AR326 and AR269 was decreased significantly by blocking with the anti-GAPDH antibody, and GAPDH restored the adhesion of AR326 and AR269 treated with trypsin. In addition, purified GAPDH significantly increased the adhesion of the strains with poor adhesion ability. These results indicated that GAPDH mediates the adhesion of these highly adhesive lactobacilli to epithelial cells and can be used to improve the adhesion ability of probiotics or other bacteria of interest.

Genomic assessment in Lactobacillus plantarum links the butyrogenic pathway with glutamine metabolism

The butyrogenic capability of Lactobacillus (L.) plantarum is highly dependent on the substrate type and so far not assigned to any specific metabolic pathway. Accordingly, we compared three genomes of L. plantarum that showed a strain-specific capability to produce butyric acid in human cells growth media. Based on the genomic analysis, butyric acid production was attributed to the complementary activities of a medium-chain thioesterase and the fatty acid synthase of type two (FASII). However, the genomic islands of discrepancy observed between butyrogenic L. plantarum strains (S2T10D, S11T3E) and the non-butyrogenic strain O2T60C do not encompass genes of FASII, but several cassettes of genes related to sugar metabolism, bacteriocins, prophages and surface proteins. Interestingly, single amino acid substitutions predicted from SNPs analysis have highlighted deleterious mutations in key genes of glutamine metabolism in L. plantarum O2T60C, which corroborated well with the metabolic deficiency suffered by O2T60C in high-glutamine growth media and its consequent incapability to produce butyrate. In parallel, the increase of glutamine content induced the production of butyric acid by L. plantarum S2T10D. The present study reveals a previously undescribed metabolic route for butyric acid production in L. plantarum, and a potential involvement of the glutamine uptake in its regulation.

Cell Surface Properties of Lactococcus lactis Reveal Milk Protein Binding Specifically Evolved in Dairy Isolates

Surface properties of bacteria are determined by the molecular composition of the cell wall and they are important for interactions of cells with their environment. Well-known examples of bacterial interactions with surfaces are biofilm formation and the fermentation of solid materials like food and feed. Lactococcus lactis is broadly used for the fermentation of cheese and buttermilk and it is primarily isolated from either plant material or the dairy environment. In this study, we characterized surface hydrophobicity, charge, emulsification properties, and the attachment to milk proteins of 55 L. lactis strains in stationary and exponential growth phases. The attachment to milk protein was assessed through a newly developed flow cytometry-based protocol. Besides finding a high degree of biodiversity, phenotype-genotype matching allowed the identification of candidate genes involved in the modification of the cell surface. Overexpression and gene deletion analysis allowed to verify the predictions for three identified proteins that altered surface hydrophobicity and attachment of milk proteins. The data also showed that lactococci isolated from a dairy environment bind higher amounts of milk proteins when compared to plant isolates. It remains to be determined whether the alteration of surface properties also has potential to alter starter culture functionalities.

Analyses of the probiotic property and stress resistance-related genes of Lactococcus lactis subsp. lactis NCDO 2118 through comparative genomics and in vitro assays

Lactococcus lactis subsp. lactis NCDO 2118 was recently reported to alleviate colitis symptoms via its anti-inflammatory and immunomodulatory activities, which are exerted by exported proteins that are not produced by L. lactis subsp. lactis IL1403. Here, we used in vitro and in silico approaches to characterize the genomic structure, the safety aspects, and the immunomodulatory activity of this strain. Through comparative genomics, we identified genomic islands, phage regions, bile salt and acid stress resistance genes, bacteriocins, adhesion-related and antibiotic resistance genes, and genes encoding proteins that are putatively secreted, expressed in vitro and absent from IL1403. The high degree of similarity between all Lactococcus suggests that the Symbiotic Islands commonly shared by both NCDO 2118 and KF147 may be responsible for their close relationship and their adaptation to plants. The predicted bacteriocins may play an important role against the invasion of competing strains. The genes related to the acid and bile salt stresses may play important roles in gastrointestinal tract survival, whereas the adhesion proteins are important for persistence in the gut, culminating in the competitive exclusion of other bacteria. Finally, the five secreted and expressed proteins may be important targets for studies of new anti-inflammatory and immunomodulatory proteins. Altogether, the analyses performed here highlight the potential use of this strain as a target for the future development of probiotic foods.

Lactobacillus fermentum ATCC 23271 Displays In vitro Inhibitory Activities against Candida spp

Lactobacilli are involved in the microbial homeostasis in the female genital tract. Due to the high prevalence of many bacterial diseases of the female genital tract and the resistance of microorganisms to various antimicrobial agents, alternative means to control these infections are necessary. Thus, this study aimed to evaluate the probiotic properties of well-characterized Lactobacillus species, including L. acidophilus (ATCC 4356), L. brevis (ATCC 367), L. delbrueckii ssp. delbrueckii (ATCC 9645), L. fermentum (ATCC 23271), L. paracasei (ATCC 335), L. plantarum (ATCC 8014), and L. rhamnosus (ATCC 9595), against Candida albicans (ATCC 18804), Neisseria gonorrhoeae (ATCC 9826), and Streptococcus agalactiae (ATCC 13813). The probiotic potential was investigated by using the following criteria: (i) adhesion to host epithelial cells and mucus, (ii) biofilm formation, (iii) co-aggregation with bacterial pathogens, (iv) inhibition of pathogen adhesion to mucus and HeLa cells, and (v) antimicrobial activity. Tested lactobacilli adhered to mucin, co-aggregated with all genital microorganisms, and displayed antimicrobial activity. With the exception of L. acidophilus and L. paracasei, they adhered to HeLa cells. However, only L. fermentum produced a moderate biofilm and a higher level of co-aggregation and mucin binding. The displacement assay demonstrated that all Lactobacillus strains inhibit C. albicans binding to mucin (p < 0.001), likely due to the production of substances with antimicrobial activity. Clinical isolates belonging to the most common Candida species associated to vaginal candidiasis were inhibited by L. fermentum. Collectively, our data suggest that L. fermentum ATCC 23271 is a potential probiotic candidate, particularly to complement candidiasis treatment, since presented with the best probiotic profile in comparison with the other tested lactobacilli strains.