Genes of Rhodobacter sphaeroides 2.4.1 regulated by innate quorum-sensing signal, 7,8-cis-N-(tetradecenoyl) homoserine lactone

J Microbiol Biotechnol. 2008 Feb;18(2):219-27.

Abstract

The free-living photoheterotrophic Gram-negative bacterium Rhodobacter sphaeroides possesses a quorumsensing (QS) regulatory system mediated by CerR-CerI, a member of the LuxR-LuxI family. To identify the genes affected by the regulatory system, random lacZ fusions were generated in the genome of R. sphaeroides strain 2.4.1 using a promoter-trapping vector, pSG2. About 20,000 clones were screened and 23 showed a significantly different level of beta- gal activities upon the addition of synthetic 7,8-cis-Ntetradecenoyl- homoserine lactone (RAI). Among these 23 clones, the clone showing the highest level of induction was selected for further study, where about a ten-fold increase of beta-gal activity was exhibited in the presence of RAI and induction was shown to be required for cerR. In this clone, the lacZ reporter was inserted in a putative gene that exhibited a low homology with catD. A genetic analysis showed that the expression of the catD homolog was initiated from a promoter of another gene present upstream of the catD. This upstream gene showed a strong homology with luxR and hence was named qsrR (quorum-sensing regulation regulator). A comparison of the total protein expression profiles for the wild-type cells and qsrR-null mutant cells using two-dimensional gel electrophoresis and a MALDI-TOF analysis allowed the identification of sets of genes modulated by the luxR homolog.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 4-Butyrolactone / analogs & derivatives*
  • 4-Butyrolactone / chemical synthesis
  • 4-Butyrolactone / metabolism
  • Bacterial Proteins / chemistry
  • Bacterial Proteins / genetics*
  • Bacterial Proteins / metabolism
  • Electrophoresis, Gel, Two-Dimensional
  • Gene Expression Regulation, Bacterial*
  • Genes, Reporter
  • Genetic Vectors / genetics
  • Molecular Sequence Data
  • Quorum Sensing*
  • Rhodobacter sphaeroides / chemistry
  • Rhodobacter sphaeroides / genetics*
  • Rhodobacter sphaeroides / metabolism

Substances

  • Bacterial Proteins
  • N-(7-tetradecenoyl)homoserine lactone
  • 4-Butyrolactone