Recently, the cross-talk between pathogenic bacteria and the intestinal epithelial cells has been a topic of discussion. For infecting intestinal epithelial cells, pathogenic gram-negative bacteria secrete virulence factors directly into the cell and then use them to modulate the various functions of the epithelial cell. In the process, the bacterium uses the type III secretion machinery to directly interact with the epithelial cell. In 1998, Kubori et al. purified the type III secretion machinery from Salmonella for the first time and clarified its supramolecular structure. It has since been identified in many other pathogenic bacteria. The analysis of type III secretion machinery has advanced rapidly, and the mystery behind host cell infection by pathogenic bacteria is gradually becoming clear. In this article, the structure and function of the Shigella type III secretion machinery are reviewed.
The diversity of acetogens in human feces was analyzed with partial formyltetrahydrofolate synthetase (FTHFS) gene sequences. FTHFS sequences affiliated with Ruminococcus productus were predominantly recovered. Several sequences of acetogens that have not previously been identified were also recovered. Analysis of FTHFS sequences is available for the study of acetogenic ecology in the human intestinal tract.