In the representative gut bacterium Lactobacillus plantarum, we identified genes encoding the enzymes involved in a saturation metabolism of polyunsaturated fatty acids and revealed in detail the metabolic pathway that generates hydroxy fatty acids, oxo fatty acids, conjugated fatty acids, and partially saturated transfatty acids as intermediates. Furthermore, we observed these intermediates, especially hydroxy fatty acids, in host organs. Levels of hydroxy fatty acids were much higher in specific pathogen-free mice than in germ-free mice, indicating that these fatty acids are generated through polyunsaturated fatty acids metabolism of gastrointestinal microorganisms. These findings suggested that lipid metabolism by gastrointestinal microbes affects the health of the host by modifying fatty acid composition.biohydrogenation | hydratase | fatty acid isomerase | conjugated linoleic acid | lipid nutrition

Background:The physiological activity of gut microbial metabolites has recently attracted much attention. Results: A gut microbial metabolite of linoleic acid, 10-hydroxy-cis-12-octadecenoic acid (HYA), ameliorates intestinal epithelial barrier impairments by regulating TNFR2 expression via the GPR40-MEK-ERK pathway. Conclusion: HYA-induced GPR40 signaling contributes to the intestinal homeostasis. Significance: Our findings indicate a novel function of GPR40 in the inflamed intestine.

We have studied the surface-enhanced Raman spectroscopy (SERS) spectrum of quinomethionate (6-methyl-1,3-dithiolo[4,5-b]quinoxalin-2-one), which is an insecticide or fungicide used on vegetables and wheat. We observed no signals in the ordinary Raman spectra of solid-state quinomethionate, but when it was adsorbed on a colloidal silver surface, strong vibrational signals were obtained at a very low concentration. The SERS spectra were obtained by silver colloids prepared by the Creighton et al. method. The influence of pH and the aggregation inductors (Cl − , Br− , F − ) on the adsorption mechanism was investigated. Two different adsorption mechanisms were deduced, depending on the experimental conditions: The one N atom or two N atoms are chemisorbed on an Ag surface. An important contribution of the chemical mechanism was inferred when the one N atom was perpendicularly adsorbed on a surface. It is possible that quinomethionate can be detected to about 10 −5 M.