Persistence and Culturability of Escherichia coli under Induced Toxin Expression

Bacteria are well known to enter dormancy under stress conditions. However, the mechanisms of different dormancy-related phenotypes are still under debate and many questions remain unanswered. This study aims to better understand the effects of toxin gene expression on the dormancy of . The effects of toxin gene expression on growth, persistence, and culturability were characterized. Specifically, we detailed dose- and time-dependent dormancy of and its susceptibility to ofloxacin via arabinose-induced toxin gene expression under the promoter. A new plot was developed to better describe the dynamic changes in culturability and persistence. The expression level of was determined using qPCR and cellular activities were monitored using fluorescence imaging and flow cytometry. High-level persister formation and strong tolerance to ofloxacin were observed after high-level induction. The new plot reveals more information than the changes in persistence alone, e.g., reduced culturability of and thus deeper dormancy under high-level induction. Consistently, controlled induction led to decreased cellular activities at promoter and an increase in the non-culturable subpopulation. Overall, this study provides new insights into dormancy induced by toxin gene expression and a more comprehensive view of persistence and culturability. The findings may help develop better control agents against dormant bacterial cells.