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.
Ceramic powder prepared by sintering of chicken feces, when mixed with avian influenza viruses or an avian adenovirus, inactivated these organisms to below detection levels. When the ceramic powder was mixed with double-distilled water, the pH of the water rose to 10 but the aqueous phase did not show any antivirus activity. After 10 washings with water or five washings with 1M Tris-HCl (pH 8.0), the ceramic powder still retained antivirus activity. Antivirus activity was not affected by the presence of organic material (33% fetal calf serum). When chicks were fed food containing 5% ceramic powder, there was no difference in body weight between normal feeding and the ceramic-mixture feeding. The mode of action of the ceramic powder remains unknown, but it possibly works by adsorbing the virus. These results show that the ceramic powder has antiviral activities and is a potentially useful tool against avian influenza on poultry farms.
A Gram-negative, non-spore-forming, ovoid to rod-shaped aerobic or microaerobic bacterium, strain 262-8 T , was isolated from a cavity within white rock collected in Antarctica. Strain 262-8 T grew at 5-30 6C (optimum 25 6C), at pH 6-8 (optimum approximately pH 7) and with 0.1-2.0 % (w/v) NaCl (optimum 0.5 % NaCl). The addition of tryptone or yeast extract was essential for growth. Strain 262-8 T was able to utilize organic compounds such as ribose, pyruvate and succinate in the presence of a low concentration of tryptone. Ubiquinone 10 was the major respiratory quinone. The major fatty acids were C 18 : 1 , C 16 : 0 and C 18 : 0 . The G+C content of the genomic DNA was 69.8 mol%. Comparative analyses of 16S rRNA gene sequences and physiological characteristics indicated that strain 262-8
A Gram-stain-negative, non-spore-forming, rod-shaped, aerobic bacterium (strain 107-E2 T ) was isolated from freshwater samples containing microbial mats collected at a lake in Skarvsnes, Antarctica (temporary lake name, Lake Tanago Ike). Strain 107-E2T grew between 5 and 25 6C,with an optimum of 23 6C. Moreover, colony formation was observed on agar media even at "5 6C. The pH range for growth was between 6.0 and 9.0, with an optimum of pH 7.0-8.0. The range of NaCl concentration for growth was between 0.0 and 0.5 % (w/v), with an optimum of 0.0 %. No growth was observed in media containing organic compounds at high concentrations, which indicated that strain 107-E2 T was an oligotroph. In the late stationary phase, strain 107-E2 T produced a dark brown water-soluble pigment. Esterase, amylase and protease production was observed. Antimicrobial-lytic activities for Gram-negative bacteria and yeast were observed. Ubiquinone-8 was the major respiratory quinone. The major fatty acids were iso-C 15 : 0 , iso-C 17 : 1 v9c and iso-C 15 : 1 at 5. The G+C content of genomic DNA was 66.1 mol%. Analysis of the 16S rRNA gene sequences revealed that strain 107-E2 T belonged to the genus Lysobacter, and low DNA-DNA relatedness values with closely related species distinguished strain 107-E2
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