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Microbiology 153 (2007), 838-846; DOI  10.1099/mic.0.2006/000638-0
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Microbiology 153 (2007), 838-846; DOI  10.1099/mic.0.2006/000638-0
© 2007 Society for General Microbiology

Heat-shock sigma factor RpoH from Geobacter sulfurreducens

Toshiyuki Ueki and Derek R. Lovley

Department of Microbiology, Morrill Science Center IV North, University of Massachusetts Amherst, 639 North Pleasant Street, Amherst, MA 01003-9298, USA

Correspondence
Toshiyuki Ueki
tueki{at}microbio.umass.edu

Recent studies with Myxococcus xanthus have suggested that homologues of the Escherichia coli heat-shock sigma factor, RpoH, may not be involved in the heat-shock response in this {delta}-proteobacterium. The genome of another {delta}-proteobacterium, Geobacter sulfurreducens, which is considered to be a representative of the Fe(III)-reducing Geobacteraceae that predominate in a diversity of subsurface environments, contains an rpoH homologue. Characterization of the G. sulfurreducens rpoH homologue revealed that it was induced by a temperature shift from 30 °C to 42 °C and that an rpoH-deficient mutant was unable to grow at 42 °C. The predicted heat-shock genes, hrcA, grpE, dnaK, groES and htpG, were heat-shock inducible in an rpoH-dependent manner, and comparison of promoter regions of these genes identified the consensus sequences for the –10 and –35 promoter elements. In addition, DNA elements identical to the CIRCE consensus sequence were found in promoters of rpoH, hrcA and groES, suggesting that these genes are regulated by a homologue of the repressor HrcA, which is known to bind the CIRCE element. These results suggest that the G. sulfurreducens RpoH homologue is the heat-shock sigma factor and that heat-shock response in G. sulfurreducens is regulated positively by RpoH as well as negatively by the HrcA/CIRCE system.

Abbreviations: CIRCE, controlling inverted repeat of chaperone expression; RNAP, RNA polymerase

The GenBank/EMBL/DDBJ accession number for the sequence reported in this paper is AAR33985.






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