The extracellular biology of the lactobacilli

D-Alanylation of teichoic acids contributes to Lactobacillus plantarum-mediated Drosophila growth during chronic undernutrition

The microbial environment influences animal physiology. However, the underlying molecular mechanisms of such functional interactions are largely undefined. Previously, we showed that during chronic undernutrition, strains of Lactobacillus plantarum, a major commensal partner of Drosophila, promote host juvenile growth and maturation partly through enhanced expression of intestinal peptidases. By screening a transposon insertion library of Lactobacillus plantarum in gnotobiotic Drosophila larvae, we identify a bacterial cell-wall-modifying machinery encoded by the pbpX2-dlt operon that is critical to enhance host digestive capabilities and promote animal growth and maturation. Deletion of this operon leads to bacterial cell wall alteration with a complete loss of D-alanylation of teichoic acids. We show that L. plantarum cell walls bearing D-alanylated teichoic acids are directly sensed by Drosophila enterocytes to ensure optimal intestinal peptidase expression and activity, juvenile growth and maturation during chronic undernutrition. We thus conclude that besides peptidoglycan, teichoic acid modifications participate in the host-commensal bacteria molecular dialogue occurring in the intestine.

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.

Genome Editing of Food-Grade Lactobacilli To Develop Therapeutic Probiotics

Lactic acid bacteria have been used historically for food manufacturing mainly to ensure preservation via fermentation. More recently, lactic acid bacteria have been exploited to promote human health, and many strains serve as industrial workhorses. Recent advances in microbiology and molecular biology have contributed to understanding the genetic basis of many of their functional attributes. These include dissection of biochemical processes that drive food fermentation, and identification and characterization of health-promoting features that positively impact the composition and roles of microbiomes in human health. Recently, the advent of clustered regularly interspaced short palindromic repeat (CRISPR)-based technologies has revolutionized our ability to manipulate genomes, and we are on the cusp of a broad-scale genome editing revolution. Here, we discuss recent advances in genetic alteration of food-grade bacteria, with a focus on CRISPR-associated enzyme genome editing, single-stranded DNA recombineering, and the modification of bacteriophages. These tools open new avenues for the genesis of next-generation biotherapeutic agents with improved genotypes and enhanced health-promoting functional features.

Interplay between Lactobacillus rhamnosus GG and Candida and the involvement of exopolysaccharides

A number of clinical studies have shown protective effects of lactobacilli against Candida species in the gastrointestinal tract, the urogenital tract and the oral cavity, while others did not show clear effects. Evidence on the mode of action of lactobacilli against Candida is also still lacking. In this study, the anti-Candida activity of the model probiotic strain Lactobacillus rhamnosus GG was explored in different assays to determine molecular interactions. We found that L. rhamnosus GG was able to interfere with Candida growth, morphogenesis and adhesion. These three aspects of Candida's physiology are all crucial to its opportunistic pathogenesis. In follow-up assays, we compared the activity of L. rhamnosus GG wild-type with its exopolysaccharide (EPS)-deficient mutant and purified EPS to evaluate the involvement of this outer carbohydrate layer. Our data demonstrate that purified EPS can both interfere with hyphal formation and adhesion to epithelial cells, which indicates that EPS is part of a combined molecular mechanism underlying the antihyphal and anti-adhesion mechanisms of L. rhamnosus GG.

Gene editing and genetic engineering approaches for advanced probiotics: A review

The applications of probiotics are significant and thus resulted in need of genome analysis of probiotic strains. Various omics methods and systems biology approaches enables us to understand and optimize the metabolic processes. These techniques have increased the researcher's attention towards gut microbiome and provided a new source for the revelation of uncharacterized biosynthetic pathways which enables novel metabolic engineering approaches. In recent years, the broad and quantitative analysis of modified strains relies on systems biology tools such as in silico design which are commonly used methods for improving strain performance. The genetic manipulation of probiotic microorganisms is crucial for defining their role in intestinal microbiota and exploring their beneficial properties. This review describes an overview of gene editing and systems biology approaches, highlighting the advent of omics methods which allows the study of new routes for studying probiotic bacteria. We have also summarized gene editing tools like TALEN, ZFNs and CRISPR-Cas that edits or cleave the specific target DNA. Furthermore, in this review an overview of proposed design of advanced customized probiotic is also hypothesized to improvise the probiotics.

In Situ β-Glucan Fortification of Cereal-Based Matrices by Pediococcus parvulus 2.6: Technological Aspects and Prebiotic Potential

Bacterial exopolysaccharides produced by lactic acid bacteria are of increasing interest in the food industry, since they might enhance the technological and functional properties of some edible matrices. In this work, Pediococcus parvulus 2.6, which produces an O2-substituted (1,3)-β-d-glucan exopolysaccharide only synthesised by bacteria, was proposed as a starter culture for the production of three cereal-based fermented foods. The obtained fermented matrices were naturally bio-fortified in microbial β-glucans, and used to investigate the prebiotic potential of the bacterial exopolysaccharide by analysing the impact on the survival of a probiotic Lactobacillus plantarum strain under starvation and gastrointestinal simulated conditions. All of the assays were performed by using as control of the P. parvulus 2.6's performance, the isogenic β-glucan non-producing 2.6NR strain. Our results showed a differential capability of P. parvulus to ferment the cereal flours. During the fermentation step, the β-glucans produced were specifically quantified and their concentration correlated with an increased viscosity of the products. The survival of the model probiotic L. plantarum WCFS1 was improved by the presence of the bacterial β-glucans in oat and rice fermented foods under starvation conditions. The probiotic bacteria showed a significantly higher viability when submitted to a simulated intestinal stress in the oat matrix fermented by the 2.6 strain. Therefore, the cereal flours were a suitable substrate for in situ bio-fortification with the bacterial β-glucan, and these matrices could be used as carriers to enhance the beneficial properties of probiotic bacteria.

Complete genome sequence of bacteriocin-producing Lactobacillus plantarum KLDS1.0391, a probiotic strain with gastrointestinal tract resistance and adhesion to the intestinal epithelial cells

Lactobacillus plantarum KLDS1.0391 is a probiotic strain isolated from the traditional fermented dairy products and identified to produce bacteriocin against Gram-positive and Gram-negative bacteria. Previous studies showed that the strain has a high resistance to gastrointestinal stress and has a high adhesion ability to the intestinal epithelial cells (Caco-2). We reported the entire genome sequence of this strain, which contains a circular 2,886,607-bp chromosome and three circular plasmids. Genes, which are related to the biosynthesis of bacteriocins, the stress resistance to gastrointestinal tract environment and adhesive performance, were identified. Whole genome sequence of Lactobacillus plantarum KLDS1.0391 will be helpful for its applications in food industry.

The Genomic Basis of Lactobacilli as Health-Promoting Organisms

Lactobacilli occupy a unique position in human culture and scientific history. Like brewer's and baker's yeast, lactobacilli have been associated with food production and preservation for thousands of years. Lactobacillus species are used in mixed microbial cultures, such as the classical Lactobacillus bulgaricus/Streptococcus thermophilus inoculum for yogurt fermentation, or combinations of diverse lactobacilli/yeasts in kefir grains. The association of lactobacilli consumption with greater longevity and improved health formed the basis for developing lactobacilli as probiotics, whose market has exploded worldwide in the past 10 years. The decade that followed the determination of the first genome sequence of a food-associated species, Lactobacillus plantarum, saw the application to lactobacilli of a full range of functional genomics methods to identify the genes and gene products that govern their distinctive phenotypes and health associations. In this review, we will briefly remind the reader of the range of beneficial effects attributed to lactobacilli, and then explain the phylogenomic basis for the distribution of these traits across the genus. Recognizing the strain specificity of probiotic effects, we review studies of intraspecific genomic variation and their contributions to identifying probiotic traits. Finally we offer a perspective on classification of lactobacilli into new genera in a scheme that will make attributing probiotic properties to clades, taxa, and species more logical and more robust.

Comparative Genomic Analysis Reveals Ecological Differentiation in the Genus Carnobacterium

Lactic acid bacteria (LAB) differ in their ability to colonize food and animal-associated habitats: while some species are specialized and colonize a limited number of habitats, other are generalist and are able to colonize multiple animal-linked habitats. In the current study, Carnobacterium was used as a model genus to elucidate the genetic basis of these colonization differences. Analyses of 16S rRNA gene meta-barcoding data showed that C. maltaromaticum followed by C. divergens are the most prevalent species in foods derived from animals (meat, fish, dairy products), and in the gut. According to phylogenetic analyses, these two animal-adapted species belong to one of two deeply branched lineages. The second lineage contains species isolated from habitats where contact with animal is rare. Genome analyses revealed that members of the animal-adapted lineage harbor a larger secretome than members of the other lineage. The predicted cell-surface proteome is highly diversified in C. maltaromaticum and C. divergens with genes involved in adaptation to the animal milieu such as those encoding biopolymer hydrolytic enzymes, a heme uptake system, and biopolymer-binding adhesins. These species also exhibit genes for gut adaptation and respiration. In contrast, Carnobacterium species belonging to the second lineage encode a poorly diversified cell-surface proteome, lack genes for gut adaptation and are unable to respire. These results shed light on the important genomics traits required for adaptation to animal-linked habitats in generalist Carnobacterium.

A non-endoscopic device to sample the oesophageal microbiota: a case-control study

BACKGROUND

The strongest risk factor for oesophageal adenocarcinoma is reflux disease, and the rising incidence of this coincides with the eradication of Helicobacter pylori, both of which might alter the oesophageal microbiota. We aimed to profile the microbiota at different stages of Barrett's carcinogenesis and investigate the Cytosponge as a minimally invasive tool for sampling the oesophageal microbiota.

METHODS

In this case-control study, 16S rRNA gene amplicon sequencing was done on 210 oesophageal samples from 86 patients representing the Barrett's oesophagus progression sequence (normal squamous controls [n=20], non-dysplastic [n=24] and dysplastic Barrett's oesophagus [n=23], and oesophageal adenocarcinoma [n=19]), relevant negative controls, and replicates on the Illumina MiSeq platform. Samples were taken from patients enrolled in the BEST2 study at five UK hospitals and the OCCAMS study at six UK hospitals. We compared fresh frozen tissue, fresh frozen endoscopic brushings, and the Cytosponge device for microbial DNA yield (qPCR), diversity, and community composition.

FINDINGS

There was decreased microbial diversity in oesophageal adenocarcinoma tissue compared with tissue from healthy control patients as measured by the observed operational taxonomic unit (OTU) richness (p=0·0012), Chao estimated total richness (p=0·0004), and Shannon diversity index (p=0·0075). Lactobacillus fermentum was enriched in oesophageal adenocarcinoma (p=0·028), and lactic acid bacteria dominated the microenvironment in seven (47%) of 15 cases of oesophageal adenocarcinoma. Comparison of oesophageal sampling methods showed that the Cytosponge yielded more than ten-times higher quantities of microbial DNA than did endoscopic brushes or biopsies using quantitative PCR (p<0·0001). The Cytosponge samples contained the majority of taxa detected in biopsy and brush samples, but were enriched for genera from the oral cavity and stomach, including Fusobacterium, Megasphaera, Campylobacter, Capnocytophaga, and Dialister. The Cytosponge detected decreased microbial diversity in patients with high-grade dysplasia in comparison to control patients, as measured by the observed OTU richness (p=0·0147), Chao estimated total richness (p=0·023), and Shannon diversity index (p=0·0085).

INTERPRETATION

Alterations in microbial communities occur in the lower oesophagus in Barrett's carcinogenesis, which can be detected at the pre-invasive stage of high-grade dysplasia with the novel Cytosponge device. Our findings are potentially applicable to early disease detection, and future test development should focus on longitudinal sampling of the microbiota to monitor for changes in microbial diversity in a larger cohort of patients.

FUNDING

Cancer Research UK, National Institute for Health Research, Medical Research Council, Wellcome Trust, The Scottish Government (RESAS).

Effects of the dietary supplementation of mixed probiotic spores of Bacillus amyloliquefaciens 54A, and Bacillus pumilus 47B on growth, innate immunity and stress responses of striped catfish (Pangasianodon hypophthalmus)

The study used the mixed probiotics of Bacillus amyloliquefaciens 54A and B. pumilus 47B isolated from striped catfish (Pangasianodon hypophthalmus) intestine aiming to stimulate growth performance, innate immunity, stress tolerance of striped catfish. The average weight gain (AWG), specific growth rate (SGR), and feed conversion ratio (FCR) were analyzed after fish were fed the mixture of probiotics (B. amyloliquefaciens 54A and B. pumilus 47B) at concentrations of 1 × 10⁸, 3 × 10⁸, and 5 × 10⁸ CFU g^-1 feed for 90 days. Immunity parameters, survival rate of fish challenged with Edwardsiella ictaluri and ammonia tolerance were also investigated. The amounts of B. amyloliquefaciens and B. pumilus were counted and identified by specific primer pairs of Ba1-F/Ba1-R, and 16-F/Bpu-R to confirm the presence of probiotics in fish intestine. The AWG (476.6 ± 7.81 g fish^-1) of fish fed probiotics at 5 × 10⁸ CFU g^-1 was significant higher than the control (390 ± 25.7 g fish^-1) after 90 days of feeding, but there was no significant (P > 0.05) effect of probiotics on FCR and SGR. Fish fed diet containing probiotics at 5 × 10⁸ CFU g^-1 also expressed resistance to E. ictaluri infection and higher immune parameters such as phagocytic activity, respiratory bursts, and lysozyme activity than the control. Stress response with ammonia showed significantly lower mortality rate (25%, 20% and 27%) of fish fed probiotics at all three levels of 1, 3 and 5 × 10⁸ CFU g^-1 than the fish fed control diet (75%). The study also demonstrated that the probiotics survived in the intestine of striped catfish after 90 days of feeding. Therefore, the dietary supplementation of a mixture of B. amyloliquefaciens and B. pumilus at 5 × 10⁸ CFU g^-1 can be used to improve the health and growth rate of striped catfish.

Isolated exopolysaccharides from Lactobacillus rhamnosus GG alleviated adipogenesis mediated by TLR2 in mice

The fibroblast cell line of 3T3-L1 was used as a cell model for screening and evaluating the feasibility of probiotic components in improving animal lipid metabolisms. The extracts from 12 Lactobacillus strains caused significantly reduced triacylglycerol (TAG) accumulation but with severe inflammation induction in 3T3-L1 adipocytes. Interestingly, exopolysaccharides (EPS) from LGG (Lactobacillus rhamnosus GG) significantly decreased the TAG accumulation without any inflammation. The anti-obesity effect of EPS was confirmed in high-fat-diets feeding mice. Fat pads of mice injected with EPS (50 mg/kg) every two days for two weeks were significantly reduced with much smaller adipocytes, compared with the counterparts. The levels of TAG and cholesterol ester in liver, as well as serum TAG, were decreased in EPS injected mice. In addition, down-regulated inflammation was observed in adipose tissue and liver. Interestingly, the expression of TLR2 in adipose tissue and 3T3-L1 cells was significantly increased by EPS addition. Moreover, the reverse of TAG accumulation in TLR2 knockdown 3T3-L1 in the presence of EPS confirmed that the inhibition effect of EPS on adipogenesis was mediated by TLR2. EPS from LGG has the potential for therapeutic development to intervene lipid metabolic disorders in mammals.

Lactobacillus johnsonii glycolipids, their structure and immunoreactivity with sera from inflammatory bowel disease patients

Structural studies of the major glycolipids produced by two Lactobacillus johnsonii (LJ) strains, LJ 151 isolated from intestinal tract of healthy mice and LJ 142 isolated from mice with experimentally induced inflammatory bowel disease (IBD), were performed. Two major glycolipids, GL1 and GL2, were present in lipid extracts from L. johnsonii 142 and 151 strains. Glycolipid GL1 has been identified as β-D-Glcp-(1→6)-α-D-Galp-(1→2)-α-D-Glcp-diglyceride and GL2 as α-D-Galp-(1→2)-α-D-Glcp-diglyceride. The main fatty acid residues identified by gas-liquid chromatography-mass spectrometry were palmitic, stearic and lactobacillic acids. Besides structural elucidation of the major glycolipids, the aim of this study was to determine the immunochemical properties of these glycolipids and to compare their immunoreactivity to that of polysaccharides obtained from the same strains. Sera from rabbits immunized with bacterial cells possessed much higher serological reactivity with polysaccharides than with glycolipids. Inversely, reactivity of the glycolipids with human sera from patients with IBD was much higher than that determined for the polysaccharides, while reactivity of glycolipids with human sera from healthy individuals was much lower than one measured for the polysaccharides. Results indicate that glycoconjugates from Lactobacillus cell wall act as antigens and may represent new IBD diagnostic biomarkers.

Beneficial microorganisms for honey bees: problems and progresses

Nowadays, honey bees are stressed by a number of biotic and abiotic factors which may compromise to some extent the pollination service and the hive productivity. The EU ban of antibiotics as therapeutic agents against bee pathogens has stimulated the search for natural alternatives. The increasing knowledge on the composition and functions of the bee gut microbiota and the link between a balanced gut microbiota and health status have encouraged the research on the use of gut microorganisms to improve bee health. Somehow, we are assisting to the transfer of the "probiotic concept" into the bee science. In this review, we examine the role of the honey bee gut microbiota in bee health and critically describe the available applications of beneficial microorganisms as pest control agents and health support. Most of the strains, mainly belonging to the genera Lactobacillus, Bifidobacterium and Bacillus, are isolated from honey bee crop or gut, but some applications involve environmental strains or formulation for animal and human consumption. Overall, the obtained results show the favourable effect of applied microbial strains on bee health and productivity, in particular if strains of bee origin are used. However, it is actually not yet possible to conclude whether this strategy will ever work. In particular, many aspects regarding the overall setup of the experiments, the dose, the timing and the duration of the treatment need to be optimized, also considering the microbiological safety of the hive products (i.e. pollen and honey). In addition, a deep investigation about the effect on host immunity and physiology is envisaged. Lastly, the final users of the formulations, i.e. beekeepers, should be taken into account for the achievement of high-quality, cost-effective and easy-to-use products.

Determination of polyphenolic profile, antioxidant activity and antibacterial properties of maqui [Aristotelia chilensis (Molina) Stuntz] a Chilean blackberry

BACKGROUND

The aim of the present study was to determine (1) the polyphenolic profile (phenolic acids, flavonoids and anthocyanins), (2) the antioxidant using four different methodologies (DPPH, ABTS, FRAP and FIC) and (3) the antibacterial properties of maqui berry [Aristotelia chilensis (Molina) Stuntz] (MB) grown in Chile.

RESULTS

The HPLC analysis of MB showed a total of 19 polyphenolic compounds identified as anthocyanins (eight compounds), flavonols (10 compounds) and ellagic acid. Delphinidin derivatives were the predominant anthocyanins while quercetin derivatives were the predominant flavonols. MB showed an antioxidant activity measured with DPPH, ABTS, FRAP and FIC methods of 28.18, 18.66, 25.22 g Trolox equivalent kg(-1) and 0.12 g ethylenediaminetetraacetic acid equivalent kg(-1) , respectively. With regard to the antibacterial activity, all strains tested were affected by MB. Aeromonas hydrophila and Listeria innocua showed the highest sensitivity to maqui berry extracts with MIC values of 40 and a 50 mg mL(-1) , respectively.

CONCLUSIONS

The results suggest that maqui berry has a great potential to be employed in the food industry as potential food ingredient to functional food development or as bio-preservative. © 2016 Society of Chemical Industry.

AcmB Is an S-Layer-Associated β-N-Acetylglucosaminidase and Functional Autolysin in Lactobacillus acidophilus NCFM

Autolysins, also known as peptidoglycan hydrolases, are enzymes that hydrolyze specific bonds within bacterial cell wall peptidoglycan during cell division and daughter cell separation. Within the genome of Lactobacillus acidophilus NCFM, there are 11 genes encoding proteins with peptidoglycan hydrolase catalytic domains, 9 of which are predicted to be functional. Notably, 5 of the 9 putative autolysins in L. acidophilus NCFM are S-layer-associated proteins (SLAPs) noncovalently colocalized along with the surface (S)-layer at the cell surface. One of these SLAPs, AcmB, a β-N-acetylglucosaminidase encoded by the gene lba0176 (acmB), was selected for functional analysis. In silico analysis revealed that acmB orthologs are found exclusively in S-layer- forming species of Lactobacillus. Chromosomal deletion of acmB resulted in aberrant cell division, autolysis, and autoaggregation. Complementation of acmB in the ΔacmB mutant restored the wild-type phenotype, confirming the role of this SLAP in cell division. The absence of AcmB within the exoproteome had a pleiotropic effect on the extracellular proteins covalently and noncovalently bound to the peptidoglycan, which likely led to the observed decrease in the binding capacity of the ΔacmB strain for mucin and extracellular matrices fibronectin, laminin, and collagen in vitro. These data suggest a functional association between the S-layer and the multiple autolysins noncovalently colocalized at the cell surface of L. acidophilus NCFM and other S-layer-producing Lactobacillus species.

IMPORTANCELactobacillus acidophilus is one of the most widely used probiotic microbes incorporated in many dairy foods and dietary supplements. This organism produces a surface (S)-layer, which is a self-assembling crystalline array found as the outermost layer of the cell wall. The S-layer, along with colocalized associated proteins, is an important mediator of probiotic activity through intestinal adhesion and modulation of the mucosal immune system. However, there is still a dearth of information regarding the basic cellular and evolutionary function of S-layers. Here, we demonstrate that multiple autolysins, responsible for breaking down the cell wall during cell division, are associated with the S-layer. Deletion of the gene encoding one of these S-layer-associated autolysins confirmed its autolytic role and resulted in reduced binding capacity to mucin and intestinal extracellular matrices. These data suggest a functional association between the S-layer and autolytic activity through the extracellular presentation of autolysins.

Stress Physiology of Lactic Acid Bacteria

Lactic acid bacteria (LAB) are important starter, commensal, or pathogenic microorganisms. The stress physiology of LAB has been studied in depth for over 2 decades, fueled mostly by the technological implications of LAB robustness in the food industry. Survival of probiotic LAB in the host and the potential relatedness of LAB virulence to their stress resilience have intensified interest in the field. Thus, a wealth of information concerning stress responses exists today for strains as diverse as starter (e.g., Lactococcus lactis), probiotic (e.g., several Lactobacillus spp.), and pathogenic (e.g., Enterococcus and Streptococcus spp.) LAB. Here we present the state of the art for LAB stress behavior. We describe the multitude of stresses that LAB are confronted with, and we present the experimental context used to study the stress responses of LAB, focusing on adaptation, habituation, and cross-protection as well as on self-induced multistress resistance in stationary phase, biofilms, and dormancy. We also consider stress responses at the population and single-cell levels. Subsequently, we concentrate on the stress defense mechanisms that have been reported to date, grouping them according to their direct participation in preserving cell energy, defending macromolecules, and protecting the cell envelope. Stress-induced responses of probiotic LAB and commensal/pathogenic LAB are highlighted separately due to the complexity of the peculiar multistress conditions to which these bacteria are subjected in their hosts. Induction of prophages under environmental stresses is then discussed. Finally, we present systems-based strategies to characterize the "stressome" of LAB and to engineer new food-related and probiotic LAB with improved stress tolerance.

Lactobacillus plantarum WCFS1 and its host interaction: a dozen years after the genome

Lactobacillus plantarum WCFS1 is one of the best studied Lactobacilli, notably as its genome was unravelled over 12 years ago. L. plantarum WCFS1 can be grown to high densities, is amenable to genetic transformation and highly robust with a relatively high survival rate during the gastrointestinal passage. In this review, we present and discuss the main insights provided by the functional genomics research on L. plantarum WCFS1 with specific attention for the molecular mechanisms related to its interaction with the human host and its potential to modify the immune system, and induce other health-related benefits. Whereas most insight has been gained in mouse and other model studies, only five human studies have been reported with L. plantarum WCFS1. Hence NCIMB 8826 (the parental strain of L. plantarum WCFS1) in human trials as to capitalize on the wealth of knowledge that is summarized here.

Strain-Specific Features of Extracellular Polysaccharides and Their Impact on Lactobacillus plantarum-Host Interactions

Lactobacilli are found in diverse environments and are widely applied as probiotic, health-promoting food supplements. Polysaccharides are ubiquitously present on the cell surface of lactobacilli and are considered to contribute to the species- and strain-specific probiotic effects that are typically observed. Two Lactobacillus plantarum strains, SF2A35B and Lp90, have an obvious ropy phenotype, implying high extracellular polysaccharide (EPS) production levels. In this work, we set out to identify the genes involved in EPS production in these L. plantarum strains and to demonstrate their role in EPS production by gene deletion analysis. A model L. plantarum strain, WCFS1, and its previously constructed derivative that produced reduced levels of EPS were included as reference strains. The constructed EPS-reduced derivatives were analyzed for the abundance and sugar compositions of their EPS, revealing cps2-like gene clusters in SF2A35B and Lp90 responsible for major EPS production. Moreover, these mutant strains were tested for phenotypic characteristics that are of relevance for their capacity to interact with the host epithelium in the intestinal tract, including bacterial surface properties as well as survival under the stress conditions encountered in the gastrointestinal tract (acid and bile stress). In addition, the Toll-like receptor 2 (TLR2) signaling and immunomodulatory capacities of the EPS-negative derivatives and their respective wild-type strains were compared, revealing strain-specific impacts of EPS on the immunomodulatory properties. Taken together, these experiments illustrate the importance of EPS in L. plantarum strains as a strain-specific determinant in host interaction.

IMPORTANCE

This study evaluates the role of extracellular polysaccharides that are produced by different strains of Lactobacillus plantarum in the determination of the cell surface properties of these bacteria and their capacity to interact with their environment, including their signaling to human host cells. The results clearly show that the consequences of removal of these polysaccharides are very strain specific, illustrating the diverse and unpredictable roles of these polysaccharides in the environmental interactions of these bacterial strains. In the context of the use of lactobacilli as health-promoting probiotic organisms, this study exemplifies the importance of strain specificity.

Structural diversity and biological significance of lipoteichoic acid in Gram-positive bacteria: focusing on beneficial probiotic lactic acid bacteria

Bacterial cell surface molecules are at the forefront of host-bacterium interactions. Teichoic acids are observed only in Gram-positive bacteria, and they are one of the main cell surface components. Teichoic acids play important physiological roles and contribute to the bacterial interaction with their host. In particular, lipoteichoic acid (LTA) anchored to the cell membrane has attracted attention as a host immunomodulator. Chemical and biological characteristics of LTA from various bacteria have been described. However, most of the information concerns pathogenic bacteria, and information on beneficial bacteria, including probiotic lactic acid bacteria, is insufficient. LTA is structurally diverse. Strain-level structural diversity of LTA is suggested to underpin its immunomodulatory activities. Thus, the structural information on LTA in probiotics, in particular strain-associated diversity, is important for understanding its beneficial roles associated with the modulation of immune response. Continued accumulation of structural information is necessary to elucidate the detailed physiological roles and significance of LTA. In this review article, we summarize the current state of knowledge on LTA structure, in particular the structure of LTA from lactic acid bacteria. We also describe the significance of structural diversity and biological roles of LTA.

Transcriptional reprogramming and phenotypic switching associated with the adaptation of Lactobacillus plantarum C2 to plant niches

Lactobacillus plantarum has been isolated from a large variety of ecological niches, thus highlighting its remarkable environmental adaptability as a generalist. Plant fermentation conditions markedly affect the functional features of L. plantarum strains. We investigated the plant niche-specific traits of L. plantarum through whole-transcriptome and phenotypic microarray profiles. Carrot (CJ) and pineapple (PJ) juices were chosen as model systems, and MRS broth was used as a control. A set of 3,122 genes was expressed, and 21 to 31% of genes were differentially expressed depending on the plant niche and cell physiological state. L. plantarum C2 seemed to specifically respond to plant media conditions. When L. plantarum was cultured in CJ, useful pathways were activated, which were aimed to sense the environment, save energy and adopt alternative routes for NAD⁺ regeneration. In PJ the acidic environment caused a transcriptional switching, which was network-linked to an acid tolerance response involving carbohydrate flow, amino acid and protein metabolism, pH homeostasis and membrane fluidity. The most prominent phenotypic dissimilarities observed in cells grown in CJ and PJ were related to carbon and nitrogen metabolism, respectively. Summarising, a snapshot of a carrot and pineapple sensing and adaptive regulation model for L. plantarum C2 was proposed.

Anti-infective activities of lactobacillus strains in the human intestinal microbiota: from probiotics to gastrointestinal anti-infectious biotherapeutic agents

A vast and diverse array of microbial species displaying great phylogenic, genomic, and metabolic diversity have colonized the gastrointestinal tract. Resident microbes play a beneficial role by regulating the intestinal immune system, stimulating the maturation of host tissues, and playing a variety of roles in nutrition and in host resistance to gastric and enteric bacterial pathogens. The mechanisms by which the resident microbial species combat gastrointestinal pathogens are complex and include competitive metabolic interactions and the production of antimicrobial molecules. The human intestinal microbiota is a source from which Lactobacillus probiotic strains have often been isolated. Only six probiotic Lactobacillus strains isolated from human intestinal microbiota, i.e., L. rhamnosus GG, L. casei Shirota YIT9029, L. casei DN-114 001, L. johnsonii NCC 533, L. acidophilus LB, and L. reuteri DSM 17938, have been well characterized with regard to their potential antimicrobial effects against the major gastric and enteric bacterial pathogens and rotavirus. In this review, we describe the current knowledge concerning the experimental antibacterial activities, including antibiotic-like and cell-regulating activities, and therapeutic effects demonstrated in well-conducted, placebo-controlled, randomized clinical trials of these probiotic Lactobacillus strains. What is known about the antimicrobial activities supported by the molecules secreted by such probiotic Lactobacillus strains suggests that they constitute a promising new source for the development of innovative anti-infectious agents that act luminally and intracellularly in the gastrointestinal tract.

Identification of Lactobacillus proteins with different recognition patterns between immune rabbit sera and nonimmune mice or human sera

Background

The genus Lactobacillus belongs to a large heterogeneous group of low G + C Gram-positive anaerobic bacteria, which are frequently used as probiotics. The health-beneficial effects, in particular the immunomodulation effect, of probiotics depend on the strain and dose used. Strain variations may be related to diversity of the cell surface architecture of bacteria and the ability to express specific antigens or secrete compounds. The use of Lactobacillus as probiotic requires a comprehensive understanding of its effect on host immune system. To evaluate the potential immunoreactive properties of proteins isolated from four Lactobacillus strains: L. johnsonii 142 and L. johnsonii 151, L. rhamnosus LOCK 0900 and L. casei LOCK 0919, the polyclonal sera obtained from mouse and human have been tested as well as with sera from rabbits immunized with whole lactobacilli cells.

Results

The reactivity of isolated proteins detected by SDS-PAGE and Western blotting was heterogeneous and varied between different serum samples. The proteins with the highest immunoreactivity were isolated, purified and sequenced, in particular the fractions were identified as phosphoglycerate kinase (L. johnsonii 142), glyceraldehyde 3-phosphate dehydrogenase (L. johnosnii 142, L. rhamnosus LOCK 0900), hypothetic protein JDM1_1307 (L. johnsonii 151) and fructose/tagatose-bisphosphate-aldolase (L. casei LOCK 0919).

Conclusion

The different prevalence of reactions against tested antigens in rabbit, mouse and human sera may indicate significant differences in immune system and commensal cross-talk in these groups. The identification of immunoreactive lactobacilli proteins opens the possibility to use them as an antigens for development of vaccines.

Identification of Surface Proteins from Lactobacillus casei BL23 Able to Bind Fibronectin and Collagen

Strains of lactobacilli show the capacity to attach to extracellular matrix proteins. Cell-wall fractions of Lactobacillus casei BL23 enriched in fibronectin, and collagen-binding proteins were isolated. Mass spectrometry analysis of their protein content revealed the presence of stress-related proteins (GroEL, ClpL), translational elongation factors (EF-Tu, EF-G), oligopeptide solute-binding proteins, and the glycolytic enzymes enolase and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The latter two enzymes were expressed in Escherichia coli and purified as glutathione-S-transferase (GST) fusion proteins, and their in vitro binding activity to fibronectin and collagen was confirmed. These results reinforce the idea that lactobacilli display on their surfaces a variety of moonlighting proteins that can be important in their adaptation to survive at intestinal mucosal sites and in the interaction with host cells.

A gastrointestinal anti-infectious biotherapeutic agent: the heat-treated Lactobacillus LB

Experimental in vitro and in vivo studies support the hypothesis that heat-treated, lyophilized Lactobacillus acidophilus LB cells and concentrated, neutralized spent culture medium conserve the variety of pharmacological, antimicrobial activities of the live probiotic strain against several infectious agents involved in well-established acute and persistent watery diarrhoea and gastritis. Heat-treated cells and heat-stable secreted molecules trigger multiple strain-specific activities explaining the therapeutic efficacy of L. acidophilus LB. This review discusses the current body of knowledge on the antimicrobial mechanisms of action exerted by L. acidophilus LB demonstrated in in vitro and in vivo experimental studies, and the evidence for the therapeutic efficacy of this anti-infectious biotherapeutic agent proved in randomized clinical trials for the treatment of acute and persistent watery diarrhoea associated with several intestinal infectious diseases in humans.

Spatial Localization and Binding of the Probiotic Lactobacillus farciminis to the Rat Intestinal Mucosa: Influence of Chronic Stress

The present study aimed at detecting the exogenously applied probiotic Lactobacillus farciminis in rats, after exposure to IBS-like chronic stress, based on 4-day Water Avoidance Stress (WAS). The presence of L. farciminis in both ileal and colonic mucosal tissues was demonstrated by FISH and qPCR, with ileum as the preferential niche, as for the SFB population. A different spatial distribution of the probiotic was observed: in the ileum, bacteria were organized in micro-colonies more or less close to the epithelium whereas, in the colon, they were mainly visualized far away from the epithelium. When rats were submitted to WAS, the L. farciminis population substantially decreased in both intestinal regions, due to a stress-induced increase in colonic motility and defecation, rather than a modification of bacterial binding to the intestinal mucin Muc2.

The role of beneficial bacteria wall elasticity in regulating innate immune response

BACKGROUND

Probiotics have great potential to contribute to development of healthy dietary regimes, preventive care, and an integrated approach to immunity-related disease management. The bacterial wall is a dynamic entity, depending on many components and playing an essential role in modulating immune response. The impact of cell wall elasticity on the beneficial effects of probiotic strains has not been sufficiently studied. The aim was to investigate the effect of lactic acid bacteria (LAB) and bifidobacteria strains on phagocytic system cells (macrophages) as related to bacterial wall elasticity, estimated using atomic force microscopy (AFM).

METHODS

We conducted studies on Balb/c line mice 18-20 g in weight using lyophilized strains of LAB-Lactobacillus acidophilus IMV B-7279, Lactobacillus casei IMV B-7280, Lactobacillus delbrueckii subsp. bulgaricus IMV B-7281, and bifidobacteria-Bifidobacterium animalis VKL and Bifidobacterium animalis VKB. We cultivated the macrophages obtained from the peritoneal cavity of mice individually with the strains of LAB and bifidobacteria and evaluated their effect on macrophages, oxygen-dependent bactericidal activity, nitric oxide production, and immunoregulatory cytokines. We used AFM scanning to estimate bacterial cell wall elasticity.

RESULTS

All strains had a stimulating effect on the functional activity of macrophages and ability to produce NO/NO2 in vitro. Lactobacilli strains increased the production of IL-12 and IFN-γ in vitro. The AFM demonstrated different cell wall elasticity levels in various strains of LAB and bifidobacteria. The rigidity of the cell walls among lactobacilli was distributed as follows: Lactobacillus acidophilus IMV B-7279 > Lactobacillus casei IMV B-7280 > Lactobacillus delbrueckii subsp. bulgaricus IMV B-7281; among the strains of bifidobacteria: B. animalis VKB > B. animalis VKL. Probiotic strain survival in the macrophages depended on the bacterial cell wall elasticity and on the time of their joint cultivation.

CONCLUSION

LAB and bifidobacteria strains stimulate immune-modulatory cytokines and active oxygen and nitrogen oxide compound production in macrophages. Strains with a more elastic cell wall according to AFM data demonstrated higher resistance to intracellular digestion in macrophages and higher level of their activation. AFM might be considered as a fast and accurate method to assess parameters of probiotic strain cell wall to predict their immune-modulatory properties.

Comparative proteomic analysis of biofilm and planktonic cells of Lactobacillus plantarum DB200

This study investigated the relative abundance of extracellular and cell wall associated proteins (exoproteome), cytoplasmic proteins (proteome), and related phenotypic traits of Lactobacillus plantarum grown under planktonic and biofilm conditions. Lactobacillus plantarum DB200 was preliminarily selected due to its ability to form biofilms and to adhere to Caco2 cells. As shown by fluorescence microscope analysis, biofilm cells became longer and autoaggregated at higher levels than planktonic cells. The molar ratio between glucose consumed and lactate synthesised was markedly decreased under biofilm compared to planktonic conditions. DIGE analysis showed a differential exoproteome (115 protein spots) and proteome (44) between planktonic and biofilm L. plantarum DB200 cells. Proteins up- or downregulated by at least twofold (p < 0.05) were found to belong mainly to the following functional categories: cell wall and catabolic process, cell cycle and adhesion, transport, glycolysis and carbohydrate metabolism, exopolysaccharide metabolism, amino acid and protein metabolisms, fatty acid and lipid biosynthesis, purine and nucleotide metabolism, stress response, oxidation/reduction process, and energy metabolism. Many of the above proteins showed moonlighting behavior. In accordance with the high expression levels of stress proteins (e.g., DnaK, GroEL, ClpP, GroES, and catalase), biofilm cells demonstrated enhanced survival under conditions of environmental stress.

Proteomic proof that a probiotic elevates glutathione level in human serum

Lactobacillus fermentum ME-3 (LfME-3) has been proven to synthesize and secrete glutathione. A regular use of the foods fermented by it has shown a favourable influence on human lipid profiles and several antioxidant parameters. We administered the LfME-3-fermented kefir for 14 days to 43 human subjects and evaluated their serum with MALDI-TOF mass spectrometer at the beginning and end of the test period. We found an increase of the peak at m/z 308 (corresponding to glutathione) and a new peak at m/z 1467.

Genomics of Weissella cibaria with an examination of its metabolic traits

Weissella is a genus of lactic acid bacteria (LAB) consisting of species formerly included in the Leuconostoc paramesenteroides group. Similar to other LAB, they are commonly found in fermented foods but have also been isolated from environmental and human samples. Currently there are 20 recognized species. Herein, three Weissella cibaria genomes were sequenced using Illumia Mi-Seq and Roche 454 technologies. Annotation was performed using the Prokka and JGI IMG pipelines. A thorough analysis of the genomics of the W. cibaria strains was performed, in addition to brief comparative analyses of the genus Weissella as a whole. Genomic sequence data from the newly sequenced W. cibaria strains and data available in GenBank for other Weissella strains was used (n = 10; four Weissella cibaria, one Weissella ceti, one Weissella confusa, one Weissella halotolerans, two Weissella koreensis and one Weissella paramesenteroides). The genomes had sizes varying from 1.3 to 2.4 Mb. DNA G+C contents ranged from 35 to 45 mol%. The core- and pan-proteome at genus and species levels were determined. The genus pan-proteome was found to comprise 4712 proteins. Analysis of the four W. cibaria genomes indicated that the core-proteome, consisting of 729 proteins, constitutes 69 % of the species pan-proteome. This large core-set may explain the divergent niches in which this species has been found. In W. cibaria, in addition to a number of phosphotransferase systems conferring the ability to assimilate plant-associated polysaccharides, an extensive proteolytic system was identified.

Impact of the exopolysaccharide layer on biofilms, adhesion and resistance to stress in Lactobacillus johnsonii FI9785

BACKGROUND

The bacterial cell surface is a crucial factor in cell-cell and cell-host interactions. Lactobacillus johnsonii FI9785 produces an exopolysaccharide (EPS) layer whose quantity and composition is altered in mutants that harbour genetic changes in their eps gene clusters. We have assessed the effect of changes in EPS production on cell surface characteristics that may affect the ability of L. johnsonii to colonise the poultry host and exclude pathogens.

RESULTS

Analysis of physicochemical cell surface characteristics reflected by Zeta potential and adhesion to hexadecane showed that an increase in EPS gave a less negative, more hydrophilic surface and reduced autoaggregation. Autoaggregation was significantly higher in mutants that have reduced EPS, indicating that EPS can mask surface structures responsible for cell-cell interactions. EPS also affected biofilm formation, but here the quantity of EPS produced was not the only determinant. A reduction in EPS production increased bacterial adhesion to chicken gut explants, but made the bacteria less able to survive some stresses.

CONCLUSIONS

This study showed that manipulation of EPS production in L. johnsonii FI9785 can affect properties which may improve its performance as a competitive exclusion agent, but that positive changes in adhesion may be compromised by a reduction in the ability to survive stress.

Synthesis and immunestimulating activity of lactobacilli-originated polysaccharide-polymeric microparticle conjugates

The design and synthesis of biomaterials capable of activating the immune system are of interest in immunology-related fields because of their ability to tune up the immune defenses of the host. Lactobacilli are a major constituent of normal human indigenous flora, and some specific strains are known to activate the immune system of the host as probiotics. In this study, we first fabricated novel biohybrid materials in which lactobacilli (L. casei strain Shirota, LcS)-originated polysaccharide-peptidoglycan complexes (PS-PGs) are conjugated with polymeric microparticles (MPs). PS-PGs conjugated onto polymeric MPs surfaces bound its specific antibody, suggesting that PS-PGs kept their original molecular recognition ability. The PS-PGs-based hybrid MPs with an appropriate density of conjugated PS-PGs effectively induced high levels of IL-12 production from macrophages without cytotoxicity. These results suggest that LcS-originated PS-PGs could be available bio-originated materials for developing novel biomaterials capable of activating the immune system in a safe manner.

Sortase-deficient lactobacilli: effect on immunomodulation and gut retention

Surface proteins of probiotic microbes, including Lactobacillus acidophilus and Lactobacillus gasseri, are believed to promote retention in the gut and mediate host-bacterial communications. Sortase, an enzyme that covalently couples a subset of extracellular proteins containing an LPXTG motif to the cell surface, is of particular interest in characterizing bacterial adherence and communication with the mucosal immune system. A sortase gene, srtA, was identified in L. acidophilus NCFM (LBA1244) and L. gasseri ATCC 33323 (LGAS_0825). Additionally, eight and six intact sortase-dependent proteins were predicted in L. acidophilus and L. gasseri, respectively. Due to the role of sortase in coupling these proteins to the cell wall, ΔsrtA deletion mutants of L. acidophilus and L. gasseri were created using the upp-based counterselective gene replacement system. Inactivation of sortase did not cause significant alteration in growth or survival in simulated gastrointestinal juices. Meanwhile, both ΔsrtA mutants showed decreased adhesion to porcine mucin in vitro. Murine dendritic cells exposed to the ΔsrtA mutant of L. acidophilus or L. gasseri induced lower levels of pro-inflammatory cytokines TNF-α and IL-12, respectively, compared with the parent strains. In vivo co-colonization of the L. acidophilus ΔsrtA mutant and its parent strain in germ-free 129S6/SvEv mice resulted in a significant one-log reduction of the ΔsrtA mutant population. Additionally, a similar reduction of the ΔsrtA mutant was observed in the caecum. This study shows for the first time that sortase-dependent proteins contribute to gut retention of probiotic microbes in the gastrointestinal tract.

In vitro assessment of the gastrointestinal tolerance and immunomodulatory function of Bacillus methylotrophicus isolated from a traditional Korean fermented soybean food

AIMS

This study aimed to investigate the potential of Bacillus methylotrophicus as a probiotic.

METHODS AND RESULTS

A Bacillus isolate designated strain C14 was isolated from Korean traditional fermented soybean paste (doenjang). The strain was identified, and its physiological and biochemical properties were characterized. The gastrointestinal tolerance and immunomodulatory function of strain C14 were also investigated. Strain C14 was identified as B. methylotrophicus by analysis of its biochemical properties using the API 50CHB system and by phylogenetic analysis of the 16S rDNA sequence. Strain C14 showed >80% and >75% of survival for artificial gastric juices (pH 2.5 and 1% pepsin) and 0.5% (w/v) bile salt, respectively. Heat-killed B. methylotrophicus C14 inhibited the adhesion of various pathogens and enhanced the adhesion of probiotic bacteria to Caco-2 cells. The heat-killed cells also induced high levels of immune cell proliferation compared with the control and stimulated interleukin-6 and tumour necrosis factor-α production in mouse macrophages.

CONCLUSIONS

Bacillus methylotrophicus C14 could be used as a probiotic.

SIGNIFICANCE AND IMPACT OF THE STUDY

Recently identified B. methylotrophicus is a new potential probiotic with high gastrointestinal tolerance.

Piliation of Lactobacillus rhamnosus GG promotes adhesion, phagocytosis, and cytokine modulation in macrophages

Recently, spaCBA-encoded pili on the cell surface of Lactobacillus rhamnosus GG were identified to be key molecules for binding to human intestinal mucus and Caco-2 intestinal epithelial cells. Here, we investigated the role of the SpaCBA pilus of L. rhamnosus GG in the interaction with macrophages in vitro by comparing the wild type with surface mutants. Our results show that SpaCBA pili play a significant role in the capacity for adhesion to macrophages and also promote bacterial uptake by these phagocytic cells. Interestingly, our data suggest that SpaCBA pili also mediate anti-inflammatory effects by induction of interleukin-10 (IL-10) mRNA and reduction of interleukin-6 (IL-6) mRNA in a murine RAW 264.7 macrophage cell line. These pili appear to mediate these effects indirectly by promoting close contact with the macrophages, facilitating the exertion of anti-inflammatory effects by other surface molecules via yet unknown mechanisms. Blockage of complement receptor 3 (CR3), previously identified to be a receptor for streptococcal pili, significantly decreased the uptake of pilus-expressing strains in RAW 264.7 cells, while the expression of IL-10 and IL-6 mRNA by these macrophages was not affected by this blocking. On the other hand, blockage of Toll-like receptor 2 (TLR2) significantly reduced the expression of IL-6 mRNA irrespective of the presence of pili.

Improvement of LysM-mediated surface display of designed ankyrin repeat proteins (DARPins) in recombinant and nonrecombinant strains of Lactococcus lactis and Lactobacillus Species

Safety and probiotic properties make lactic acid bacteria (LAB) attractive hosts for surface display of heterologous proteins. Protein display on nonrecombinant microorganisms is preferred for therapeutic and food applications due to regulatory requirements. We displayed two designed ankyrin repeat proteins (DARPins), each possessing affinity for the Fc region of human IgG, on the surface of Lactococcus lactis by fusing them to the Usp45 secretion signal and to the peptidoglycan-binding C terminus of AcmA, containing lysine motif (LysM) repeats. Growth medium containing a secreted fusion protein was used to test its heterologous binding to 10 strains of species of the genus Lactobacillus, using flow cytometry, whole-cell enzyme-linked immunosorbent assay (ELISA), and fluorescence microscopy. The fusion proteins bound to the surfaces of all lactobacilli; however, binding to the majority of bacteria was only 2- to 5-fold stronger than that of the control. Lactobacillus salivarius ATCC 11741 demonstrated exceptionally strong binding (32- to 55-fold higher than that of the control) and may therefore be an attractive host for nonrecombinant surface display. Genomic comparison of the species indicated the exopolysaccharides of Lb. salivarius as a possible reason for the difference. Additionally, a 15-fold concentration-dependent increase in nonrecombinant surface display on L. lactis was demonstrated by growing bacteria with sublethal concentrations of the antibiotics chloramphenicol and erythromycin. Nonrecombinant surface display on LAB, based on LysM repeats, was optimized by selecting Lactobacillus salivarius ATCC 11741 as the optimal host and by introducing antibiotics as additives for increasing surface display on L. lactis. Additionally, effective display of DARPins on the surfaces of nonrecombinant LAB has opened up several new therapeutic possibilities.

Cell-bound exopolysaccharides of Lactobacillus brevis KB290 enhance cytotoxic activity of mouse splenocytes

AIMS

This study aimed to identify the main active component of Lactobacillus brevis KB290 (KB290) that is responsible for enhanced cell-mediated cytotoxic activity of mouse splenocytes Live KB290, a probiotic strain derived from a Japanese traditional pickle, was previously reported to modulate innate immune responses as affecting on cell-mediated cytotoxic activity of mouse splenocytes.

METHODS AND RESULTS

We used live KB290, heat-killed KB290, a derivative strain (Lact. brevis KB392) with different amounts of cell-bound exopolysaccharide (EPS-b), and a crude extract of EPS-b from KB290 cell surface. Female BALB/c mice were fed a diet containing 10(10) CFU live KB290, 10(10) CFU live KB392, 15 mg heat-killed KB290 or 600 μg crude extract of EPS-b for 1 day. Live KB290 (P < 0.01), heat-killed KB290 (P < 0.05) and crude EPS-b at 600 μg (P < 0.05) per mouse significantly enhanced cytotoxic activity; however, live KB392 had no effect.

CONCLUSIONS

Both live and heat-killed KB290 and crude EPS-b significantly enhanced cytotoxic activity of mouse splenocytes.

SIGNIFICANCE AND IMPACT OF THE STUDY

We demonstrated that EPS-b produced by KB290 has a critical role in enhancing cell-mediated cytotoxic activity in mouse spleen.

Environmentally determined differences in the murine lung microbiota and their relation to alveolar architecture

Commensal bacteria control the micro-ecology of metazoan epithelial surfaces with pivotal effect on tissue homeostasis and host defense. In contrast to the upper respiratory tract, the lower respiratory tract of healthy individuals has largely been considered free of microorganisms. To understand airway micro-ecology we studied microbiota of sterilely excised lungs from mice of different origin including outbred wild mice caught in the natural environment or kept under non-specific-pathogen-free (SPF) conditions as well as inbred mice maintained in non-SPF, SPF or germ-free (GF) facilities. High-throughput pyrosequencing of reverse transcribed 16S rRNA revealed metabolically active murine lung microbiota in all but GF mice. The overall composition across samples was similar at the phylum and family level. However, species richness was significantly different between lung microbiota from SPF and non-SPF mice. Non-cultivatable Betaproteobacteria such as Ralstonia spp. made up the major constituents and were also confirmed by 16S rRNA gene cloning analysis. Additionally, Pasteurellaceae, Enterobacteria and Firmicutes were isolated from lungs of non-SPF mice. Bacterial communities were detectable by fluorescent in situ hybridization (FISH) at alveolar epithelia in the absence of inflammation. Notably, higher bacterial abundance in non-SPF mice correlated with more and smaller size alveolae, which was corroborated by transplanting Lactobacillus spp. lung isolates into GF mice. Our data indicate a common microbial composition of murine lungs, which is diversified through different environmental conditions and affects lung architecture. Identification of the microbiota of murine lungs will pave the path to study their influence on pulmonary immunity to infection and allergens using mouse models.

Phenotypic surface properties (aggregation, adhesion and biofilm formation) and presence of related genes in beneficial vaginal lactobacilli

AIMS

To evaluate the phenotypic expression of auto-aggregation, adhesion to mucin and biofilm formation of lactobacilli isolated from human vagina and the presence of related genes.

METHODS AND RESULTS

Seven different strains of three Lactobacillus species (Lactobacillus gasseri, Lactobacillus rhamnosus and Lactobacillus reuteri) were evaluated. The auto-aggregation property was determined by spectrophotometric assay and flow cytometry. Adhesion and biofilm formation were assayed by crystal violet staining. The presence of the genes encoding sortases, pilin subunits and surface proteins was evaluated by polymerase chain reactions. The two Lact. reuteri strains assayed showed high auto-aggregation, adhesion to mucin and biofilm formation ability. In these strains, the genes encoding three adhesion proteins were identified. In Lact. rhamnosus CRL (Centro de Referencia para Lactobacilos Culture Collection) 1332, pilus-encoding genes were detected. In all Lact. rhamnosus strains assayed, two genes encoding for other surface proteins related to adhesion and biofilm formation were detected.

CONCLUSIONS

The vaginal lactobacilli assayed exhibited phenotypic and genetic characteristics that were specific for each strain.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first study on auto-aggregation, adhesion and biofilm formation of vaginal Lactobacillus strains by phenotypic and genetic assays.