Heat-shock sigma factor RpoH from Geobacter sulfurreducens

Microbiology (Reading). 2007 Mar;153(Pt 3):838-846. doi: 10.1099/mic.0.2006/000638-0.


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 degrees C to 42 degrees C and that an rpoH-deficient mutant was unable to grow at 42 degrees 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.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adaptation, Physiological
  • Base Sequence
  • Binding Sites
  • Consensus Sequence / genetics
  • DNA, Bacterial / chemistry
  • DNA, Bacterial / genetics
  • Gene Expression Regulation, Bacterial
  • Genome, Bacterial
  • Geobacter / genetics*
  • Geobacter / physiology*
  • Heat-Shock Proteins / biosynthesis*
  • Heat-Shock Proteins / genetics*
  • Hot Temperature
  • Molecular Sequence Data
  • Promoter Regions, Genetic
  • RNA, Bacterial / analysis
  • RNA, Messenger / analysis
  • Sigma Factor / biosynthesis*
  • Sigma Factor / genetics*
  • Transcription, Genetic


  • DNA, Bacterial
  • Heat-Shock Proteins
  • RNA, Bacterial
  • RNA, Messenger
  • Sigma Factor
  • heat-shock sigma factor 32

Associated data

  • GENBANK/AAR33985