A genetic analysis of the response of Escherichia coli to cobalt stress.
Cobalt can be toxic and the way cells adapt to its presence is largely unknown. Here we carried out a transcriptomic analysis of Escherichia coli exposed to cobalt. A limited number of genes were either up- or downregulated. Upregulated genes include the isc and the nfuA genes encoding Fe/S biogenesis assisting factors, and the rcnA gene encoding a cobalt efflux system. Downregulated genes are implicated in anaerobic metabolism (narK, nirB, hybO, grcA), metal transport (feoB, nikA), sulfate/thiosulfate import (cysP), and one is of unknown function (yeeE). Cobalt regulation of isc, nfuA, hybO, cysP and yeeE genes was found to involve IscR, a Fe/S transcriptional regulator. Previously, the Suf Fe/S biogenesis machinery was found to be important for cobalt stress adaptation, but suf genes did not show up in the microarray analysis. Therefore, we used qRT-PCR analysis and found that cobalt induced the suf operon expression. Moreover, kinetic analysis of the cobalt-mediated induction of the suf operon expression allowed us to propose that cobalt toxicity is caused first by impaired Fe/S biogenesis, followed by decreased iron bioavailability and eventually oxidative stress.
Fantino
Jean-Raphaël
JR
Laboratoire de Chimie Bactérienne, CNRS UPR-9043, Institut de Microbiologie de la Méditerranée, 31 Chemin Joseph Aiguier, 13009 Marseille, France.
Py
Béatrice
B
Fontecave
Marc
M
Barras
Frédéric
F
D003035:Cobalt / Q000494:pharmacology*; D015536:Down-Regulation / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D018384:Oxidative Stress / Q000235:genetics*; D016133:Polymerase Chain Reaction; D014131:Trace Elements / Q000494:pharmacology*; D014157:Transcription Factors / Q000235:genetics; D015854:Up-Regulation / Q000235:genetics
D029968:Escherichia coli Proteins; C499695:IscR protein, E coli; D014131:Trace Elements; D014157:Transcription Factors; D003035:Cobalt