Obesity is a disease with a rapidly increasing prevalence all over the world in recent years. Genetic and environmental factors are involved in the etiology of obesity, and the effect of microbiota on obesity is becoming increasingly clear. Obesity treatment has various treatment modalities such as behavior modification, medical nutrition therapy, physical activity enhancement, and surgical intervention. When other treatment methods are not successful, bariatric surgery is usually resorted to as the treatment method. Some changes such as food choices, the level of hormones and enzymes due to anatomical changes, pH of the stomach, and microbiota are observed after bariatric surgery. Alteration in the microbiota composition after bariatric surgery has also been reported to be important in achieving body weight loss and preserving body weight loss.

Properties of Lactobacillus plantarum group strains isolated from two kinds of Japanese post-fermented teas, Ishizuchi-kurocha and Awa-bancha, were compared. Although lactic acid bacteria isolated from the fermented teas were identified as L. plantarum via homology comparison of 16S ribosomal RNA gene sequences, classification of L. plantarum based on ribosomal proteins showed that the strains isolated from Ishizuchi-kurocha and Awa-bancha were different. According to classification by the ribosomal protein typing, Ishizuchi-kurocha-derived strains belong to the same group as L. plantarum subsp. plantarum JCM 1149^T. Awa-bancha-derived strains were assigned to a different group. This pattern was also applicable to strains isolated more than 10 years ago. A further analysis based on recA and a dnaK gene showed that Awa-bancha-derived strains were closely related to L. pentosus. The interactions with cultured cells were different between strain JCM 1149^T and the Ishizuchi-kurocha-derived strains. The Ishizuchi-kurocha-derived strains showed strong adhesion to Caco-2 cells. In contrast, strain JCM 1149^T and the Awa-bancha-derived strains hardly adhered to Caco-2 cells. According to the ribosomal protein typing, sugar utilization, and interaction with Caco-2 cells, although these properties were dependent on the strain strictly speaking, the L. plantarum group strains in this study can be subdivided into two groups: (1) type strain JCM 1149^T and Ishizuchi-kurocha-derived strains and (2) Awa-bancha-derived strains. A regionally unique microorganism may persist in each traditional fermented drink.

Immunoglobulin (Ig) A in the mucus of the intestinal tract plays an important role in preventing the invasion of pathogenic microorganisms and regulating the composition of the gut microbiota. Several strains of probiotic lactic acid bacteria (LAB) are known to promote intestinal IgA production. Bacteria are also known to naturally release spherical membrane vesicles (MVs) that are involved in various biological functions such as quorum sensing, pathogenesis, and host immunomodulation. However, the production of MVs by LAB and their effects on host immunity remain poorly understood. In this study, we investigated the MV production by Lactobacillus sakei subsp. sakei NBRC15893 isolated from kimoto, the traditional seed mash used for brewing sake. MVs were separated from the culture broth of L. sakei NBRC15893 through filtration and density gradient ultracentrifugation and were observed by transmission electron microscopy. The MVs showed a spherical morphology, with a diameter of 30–400 nm, and contained proteins and nucleic acids. In addition, both the LAB cells and purified MVs promoted IgA production by murine Peyer’s patch cells. This MV- and cell-induced IgA production was suppressed by neutralization of Toll-like receptor (TLR) 2, which recognizes cell wall components of gram-positive bacteria, using an anti-TLR2 antibody. Collectively, our results indicate that MVs released from L. sakei NBRC15893 enhance IgA production by activating host TLR2 signaling through its cell wall components. Thus, it is important to consider novel interactions between gut microbiota and hosts via MVs, and MVs derived from probiotic bacteria could have promising applications as safe adjuvants.

The incidence of Clostridium difficile infection (CDI) is greater in elderly orthopedic patients. We conducted a retrospective case-control study by selecting elderly patients who underwent proximal femoral fracture surgery to investigate the effect of probiotics on CDI prevention. Cases were diagnosed with CDI by an enzyme-linked immunosorbent assay for C. difficile toxins using frozen stool specimens. The primary method of exposure was receipt of combination probiotics such as Streptococcus faecalis, Bacillus mesentericus, and Clostridium butyricum. The crude odds ratio between developing CDI and receiving combination probiotics was 0.074 (95% CI: 0.010–0.565; p=0.002). Adjunctive combination probiotics among elderly patients who undergo proximal femoral fracture surgery likely reduces the probability of CDI.

We aimed to determine whether the composition of the fecal microbiota changes under hyperbaric conditions. In this study, we collected fecal samples from 6 healthy divers at three points during deep diving training (before, 2.1 MPa, end). The frequency of Clostridium cluster XVIII tended to be increased after compression. The frequencies of Clostridium cluster IV and subcluster XIVa were inversely correlated with that of Bacteroides. The compositional changes in the fecal microbiota exhibited interindividual variability. These findings suggest that hyperbaric conditions affect the fecal microbiota.