Circadian programs in cyanobacteria: adaptiveness and mechanism

Annu Rev Microbiol. 1999;53:389-409. doi: 10.1146/annurev.micro.53.1.389.


At least one group of prokaryotes is known to have circadian regulation of cellular activities--the cyanobacteria. Their "biological clock" orchestrates cellular events to occur in an optimal temporal program, and it can keep track of circadian time even when the cells are dividing more rapidly than once per day. Growth competition experiments demonstrate that the fitness of cyanobacteria is enhanced when the circadian period matches the period of the environmental cycle. Three genes have been identified that specifically affect circadian phenotypes. These genes, kaiA, kaiB, and kaiC, are adjacent to each other on the chromosome, thus forming a clock gene cluster. The clock gene products appear to interact with each other and form an autoregulatory feedback loop.

Publication types

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

MeSH terms

  • Adaptation, Physiological*
  • Amino Acid Sequence
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Biological Clocks / genetics
  • Biological Clocks / physiology
  • Circadian Rhythm Signaling Peptides and Proteins
  • Circadian Rhythm* / genetics
  • Circadian Rhythm* / physiology
  • Cyanobacteria / genetics
  • Cyanobacteria / physiology*
  • Evolution, Molecular
  • Gene Expression Regulation, Bacterial
  • Molecular Sequence Data


  • Bacterial Proteins
  • Circadian Rhythm Signaling Peptides and Proteins
  • KaiC protein, cyanobacteria