Orphan LuxR regulators of quorum sensing

FEMS Microbiol Rev. 2009 Jul;33(4):739-56. doi: 10.1111/j.1574-6976.2009.00163.x. Epub 2009 Apr 15.


Bacteria can modulate their behavior by releasing and responding to the accumulation of signal molecules. This population co-ordination, referred to as quorum sensing, is prevalent in Gram-negative and Gram-positive bacteria. The essential constituents of quorum-sensing systems include a signal producer, or synthase, and a cognate transcriptional regulator that responds to the accumulated signal molecules. With the availability of bacterial genome sequences and an increased elucidation of quorum-sensing circuits, genes that code for additional transcriptional regulators, usually in excess of the synthase, have been identified. These additional regulators are referred to as 'orphan' regulators, because they are not directly associated with a synthase. Here, we review orphan regulators characterized in various Gram-negative bacteria and their role in expanding the bacterial regulatory network.

Publication types

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

MeSH terms

  • Amino Acid Sequence
  • Gene Expression Regulation, Bacterial*
  • Gram-Negative Bacteria / chemistry
  • Gram-Negative Bacteria / classification
  • Gram-Negative Bacteria / genetics
  • Gram-Negative Bacteria / physiology*
  • Molecular Sequence Data
  • Phylogeny
  • Quorum Sensing*
  • Repressor Proteins / chemistry
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism*
  • Trans-Activators / chemistry
  • Trans-Activators / genetics
  • Trans-Activators / metabolism*


  • Repressor Proteins
  • Trans-Activators
  • LuxR autoinducer binding proteins