RNA-seq-based monitoring of gene expression changes of viable but non-culturable state of Vibrio cholerae induced by cold seawater.

Vibrio cholerae O1 is a natural inhabitant of aquatic environments and causes the acute diarrheal disease cholera. Entry into a viable but non-culturable (VBNC) state is a survival strategy by which V. cholerae withstands natural stresses and is important for the transition between the aquatic and host environments during the V. cholerae life cycle. In this study, the formation of VBNC V. cholerae induced by cold seawater exposure was investigated using RNA sequencing (RNA-seq). The analysis revealed that the expression of 1420 genes was changed on VBNC state formation. In the VBNC cells, genes related to biofilm formation, chitin utilization and stress responses were upregulated, whereas those related to cell division, morphology and ribosomal activity were mainly downregulated. The concurrent acquisition of a carbon source and the arrest of cell division in cells with low metabolic activity help bacteria increase their resistance to unfavourable environments. Moreover, two transcriptional regulators, SlmA and MetJ, were found to play roles in both VBNC formation and intestinal colonization, suggesting that some genes may function in both processes. This acquired knowledge will improve our understanding of the molecular mechanisms of stress tolerance and may help control future cholera infections and outbreaks.