Molecular switches--the ON and OFF of bacterial phase variation

Mol Microbiol. 1999 Sep;33(5):919-32. doi: 10.1046/j.1365-2958.1999.01555.x.


The expression of most bacterial genes is controlled at the level of transcription via promoter control mechanisms that permit a graded response. However, an increasing number of bacterial genes are found to exhibit an 'all-or-none' control mechanism that adapts the bacterium to more than one environment. One such mechanism is phase variation, traditionally defined as the high-frequency ON<-->OFF switching of phenotype expression. Phase variation events are usually random, but may be modulated by environmental conditions. The mechanisms of phase variation events and their significance within the microbial community are discussed here.

Publication types

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

MeSH terms

  • Adaptation, Physiological / genetics*
  • Amino Acid Sequence
  • Bacteria / genetics*
  • Base Sequence
  • Gene Expression Regulation, Bacterial*
  • Molecular Sequence Data
  • Protein Biosynthesis
  • Recombination, Genetic*
  • Transcription, Genetic