Genes of Rhodobacter sphaeroides 2.4.1 regulated by innate quorum-sensing signal, 7,8-cis-N-(tetradecenoyl) homoserine lactone.
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.
Hwang
Won
W
Department of Life Science and Interdisciplinary Program of Integrated Biotechnology, Sogang University, Seoul 121-742, Korea.
Lee
Ko-Eun
KE
Lee
Jeong Kug
JK
Park
Byoung Chul
BC
Kim
Kun-Soo
KS
D015107:4-Butyrolactone / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D015964:Gene Expression Regulation, Bacterial; D017930:Genes, Reporter; D005822:Genetic Vectors / Q000235:genetics; D008969:Molecular Sequence Data; D053038:Quorum Sensing; D012242:Rhodobacter sphaeroides / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
D001426:Bacterial Proteins; C109408:N-(7-tetradecenoyl)homoserine lactone; D015107:4-Butyrolactone