Exopolysaccharide Produced by Lactobacillus casei Promotes the Differentiation of CD4+ T Cells into Th17 Cells in BALB/c Mouse Peyer's Patches in Vivo and in Vitro

The immunomodulatory activity of a few Lactobacillus exopolysaccharides (EPS) has been reported. However, whether Lactobacillus EPS can promote the differentiation of CD4 T lymphocytes (CD4⁺T) cells into T-helper 17 cells (Th17 cells) in the Peyer's Patches (PPs) of mice has not been addressed. In this study, we found the molecular weight (M_w) of the purified EPS from L. casei ranged from 2.7 × 10⁶ Da to 1.7 × 10⁷ Da, and the average M_w was approximately 8.4 × 10⁶ Da. In healthy BALB/c mice, EPS elevated the numbers of Th17 cells and levels of Th17-related cytokines. In vitro, EPS induced BMDCs to stimulate the differentiation of CD4⁺T cells of PPs into Th17 cells and the related cytokine secretions. Results suggest that L. casei EPS can effectively induce and promote the differentiation of CD4⁺T cells of PPs into Th17 cells in healthy mice and has the potential ability to improve intestinal mucosa immunity.

The microbiome of the invertebrate model host Galleria mellonella is dominated by Enterococcus

Background

The popularity of Galleria mellonella as invertebrate model is increasing rapidly, because it forms an attractive alternative to study bacterial, fungal and viral infections, toxin biology, and to screen antimicrobial drugs. For a number of vertebrate and invertebrate animal and plant models, it has been established that the commensals present within the microbial communities on various host surfaces will influence the host’s immune and growth development state and the colonization capacity of newly introduced micro-organisms. The microbial communities of Galleria mellonella larvae have, however, not yet been well characterized.

Results

In this study, we present the bacterial communities that were found by 16S rRNA amplicon sequencing on different body sites of G. mellonella larvae. These communities showed very little diversity and were mostly dominated by one Enterococcus taxon. In addition, we found that the production conditions (as ‘bait’ for fishing or under more controlled ‘research grade’ conditions - with or without hormones and antibiotics) appear to have little impact on the microbiota of the larvae.

Conclusions

Establishment of the simplicity of the microbiota of G. mellonella larvae underlines the potential of the larvae as a model host system for microbiome-host interactions.

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.