Recently, the research team of Nankai University revealed an important mechanism in the evolution of enterohemorrhagic E. coli (EHEC) O157:H7, an important enteropathogenic microorganism. It was found that this pathogenic bacterium evolves to acquire a unique two-component regulatory system (RbfSR) to develop the ability to sense microbiota-produced riboflavin in the large intestine of the host, thereby improving its virulence. At the same time, the findings suggest that other EHEC strains may evolve to form highly pathogenic strains by acquiring RbfSR, thus posing potential public health risks. The results were published online in the world-renowned academic journal Proceedings of the National Academy of Sciences (PNAS) on November 22. 

Figure: Molecular mechanism of EHECO157:H7 enhancing pathogenicity in the gut by sensing riboflavin produced by the intestinal flora

As a result of extensive comparative genomes and comparative transcriptome analysis as well as biological experiments, the research team found that the most pathogenic serotype O157:H7 in EHEC acquires a unique two-component regulatory system (RbfSR) in the early stage of evolution and has been preserved even today. RbfSR enables EHEC O157:H7 to sense riboflavin produced by the intestinal flora in the host's large intestine, thereby activating the expression of its key pathogenic agents in a site-specific manner, and improving bacterial pathogenicity. These results reveal that obtaining RbfSR is a critical step in the formation of highly pathogenic O157:H7. Moreover, the team found that when other EHEC strains obtain RbfSR, their pathogenicity is significantly enhanced. Due to the highly frequent lateral DNA transfer among gut bacteria, special attention shall be drawn to this potential public health risk. This work has further improved people's knowledge and understanding of the evolutionary law and pathogenic mechanism of enteropathogenic microorganisms. 

Professor Wang Lei of Nankai University is the corresponding author of the paper, Professor Liu Bin is the first and co-corresponding author, postdoc fellow Liu Yutao is the co-first author, and Professor Zhu Siwei is the co-author of the paper. 

Link to the paper: www.pnas.org/doi/10.1073/pnas.2212436119

(Edited and translated by Nankai News Team)