Genomics of the ccoNOQP-encoded cbb3 oxidase complex in bacteria

Arch Microbiol. 2004 Feb;181(2):89-96. doi: 10.1007/s00203-003-0641-5. Epub 2004 Jan 9.


Many bacteria adapt to microoxic conditions by synthesizing a particular cytochrome c oxidase (cbb3) complex with a high affinity for O2, encoded by the ccoNOQP operon. A survey of genome databases indicates that ccoNOQP sequences are widespread in all sub-branches of Proteobacteria but otherwise are found only in bacteria of the CFB group ( Cytophaga, Flexibacter, Bacteroides). Our analysis of available genome sequences suggests four major strategies of regulating ccoNOQP expression in response to O2. The most widespread strategy involves direct regulation by the O2-responsive protein Fnr. The second strategy involves an O2-insensitive paralogue of Fnr, FixK, whose expression is regulated by the O2-responding FixLJ two-component system. A third strategy of mixed regulation operates in bacteria carrying both fnr and fixLJ-fixKgenes. Another, not yet identified, strategy is likely to operate in the epsilon-Proteobacteria Helicobacter pylori and Campylobacter jejuni which lack fnr and fixLJ-fixK genes. The FixLJ strategy appears specific for the alpha-subclass of Proteobacteria but is not restricted to rhizobia in which it was originally discovered.

Publication types

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

MeSH terms

  • Bacteria / enzymology*
  • Bacteria / genetics*
  • Bacterial Proteins / genetics
  • Bacterial Proteins / physiology
  • Electron Transport Complex IV / genetics*
  • Gene Expression Regulation, Bacterial
  • Hemeproteins / genetics
  • Hemeproteins / physiology
  • Histidine Kinase
  • Operon
  • Oxygen / metabolism
  • Transcription Factors / genetics
  • Transcription Factors / physiology


  • Bacterial Proteins
  • Hemeproteins
  • Transcription Factors
  • FixK protein, Bacteria
  • FixJ protein, Bacteria
  • cbb3 oxidase
  • Electron Transport Complex IV
  • FixL protein, Bacteria
  • Histidine Kinase
  • Oxygen