Transcriptional responses of Escherichia coli during recovery from inorganic or organic mercury exposure. Escherichia coli str. K-12 substr. MG1655

Gene expression changes during exponential growth of E. coli MG1655 were compared by RNA-seq after sub-acute exposure to inorganic mercuric chloride (HgCl2) or to the organomercurial, phenylmercuric-acetate (PMA). Differential gene expression revealed common and distinct responses to the mercurials from initial growth stasis through subsequent recovery. Sub-acute mercurial exposures affected expression of ~45% of all genes, many reflecting distinct biochemical damage by each mercurial and the corresponding cellular resources available for recovery of normal growth. Overall design: RNA-Seq and differential gene expression analysis were used to compare the effects of sub-acute inorganic and organic mercury exposure in E. coli throughout recovery. Sub-acute exposure was operationally defined as the concentration of mercury that clearly inhibited growth relative to the unexposed control, but allowed cells to resume growth within 1 hour or approximately one generation in Neidhart MOPS minimal medium. The effects of exposure to HgCl2 (n=3) or PMA (n=3) were examined in E. coli and differential gene expression was determined for each condition by performing pair-wise comparisons to unexposed E. coli culture (n=3) at corresponding time point (10, 30, and 60 min) following exposure. Comparisons were also made to determine differential expression in unexposed culture over time, not influenced by mercury exposure.