Adaptation of anaerobic cultures of Escherichia coli K‐12 in response to environmental trimethylamine‐N‐oxide. (3rd February 2015)

• Record Type: Journal Article
• Authors: Denby, Katie J.; Rolfe, Matthew D.; Crick, Ellen; Sanguinetti, Guido; Poole, Robert K.; Green, Jeffrey
• Is Part Of: Environmental microbiology. Volume 17:Number 7(2015:Jul.)
• Page Start: 2477
• Page End: 2491
• Publication Date: 2015-02-03
• Subjects: Microbial ecology -- Periodicals; Environmental Microbiology -- Periodicals; 579.17
• DOI: 10.1111/1462-2920.12726
• Languages: English
• ISSNs: 1462-2912

Abstract

<abstract abstract-type="main"> <title>Summary</title> <p>Systematic analyses of transcriptional and metabolic changes occurring when <italic>E</italic><italic>scherichia coli</italic> K‐12 switches from fermentative growth to anaerobic respiratory growth with trimethylamine‐N‐oxide (TMAO) as the terminal electron acceptor revealed: (i) the induction of <italic>torCAD</italic>, but not genes encoding alternative TMAO reductases; (ii) transient expression of <italic>frmRAB</italic>, encoding formaldehyde dehydrogenase; and (iii) downregulation of copper resistance genes. Simultaneous inference of 167 transcription factor (TF) activities implied that transcriptional re‐programming was mediated by 20 TFs, including the transient inactivation of the two‐component system ArcBA; a prediction validated by direct measurement of phosphorylated ArcA. Induction of <italic>frmRAB</italic>, detection of dimethylamine in culture medium and formaldehyde production when cell‐free extracts were incubated with TMAO suggested the presence of TMAO demethylase activity. Accordingly, the viability of an <italic>frmRAB</italic> mutant was compromised upon exposure to TMAO. Downregulation of genes involved in copper resistance could be accounted for by TMAO inhibition of Cu(II) reduction. The simplest interpretation of the data is that during adaptation to the presence of environmental TMAO, anaerobic fermentative cultures of <italic>E</italic><italic>. coli</italic> respond by activating the TorTSR regulatory system with consequent induction of TMAO reductase activity, resulting in net oxidation of menaquinone and inhibition of Cu(II) reduction, responses that are sensed by ArcBA and CusRS respectively.</p> </abstract>