These authors contributed equally to this work.
A complex LuxR–LuxI type quorum sensing network in a roseobacterial marine sponge symbiont activates flagellar motility and inhibits biofilm formation
Article first published online: 18 JUL 2012
© 2012 Blackwell Publishing Ltd
Volume 85, Issue 5, pages 916–933, September 2012
How to Cite
Zan, J., Cicirelli, E. M., Mohamed, N. M., Sibhatu, H., Kroll, S., Choi, O., Uhlson, C. L., Wysoczynski, C. L., Murphy, R. C., Churchill, M. E. A., Hill, R. T. and Fuqua, C. (2012), A complex LuxR–LuxI type quorum sensing network in a roseobacterial marine sponge symbiont activates flagellar motility and inhibits biofilm formation. Molecular Microbiology, 85: 916–933. doi: 10.1111/j.1365-2958.2012.08149.x
- Issue published online: 26 AUG 2012
- Article first published online: 18 JUL 2012
- Accepted manuscript online: 28 JUN 2012 12:00AM EST
- Accepted 20 June, 2012.
Bacteria isolated from marine sponges, including the Silicibacter–Ruegeria (SR) subgroup of the Roseobacter clade, produce N-acylhomoserine lactone (AHL) quorum sensing signal molecules. This study is the first detailed analysis of AHL quorum sensing in sponge-associated bacteria, specifically Ruegeria sp. KLH11, from the sponge Mycale laxissima. Two pairs of luxR and luxI homologues and one solo luxI homologue were identified and designated ssaRI, ssbRI and sscI (sponge-associated symbiont locus A, B and C, luxR or luxI homologue). SsaI produced predominantly long-chain 3-oxo-AHLs and both SsbI and SscI specified 3-OH-AHLs. Addition of exogenous AHLs to KLH11 increased the expression of ssaI but not ssaR, ssbI or ssbR, and genetic analyses revealed a complex interconnected arrangement between SsaRI and SsbRI systems. Interestingly, flagellar motility was abolished in the ssaI and ssaR mutants, with the flagellar biosynthesis genes under strict SsaRI control, and active motility only at high culture density. Conversely, ssaI and ssaR mutants formed more robust biofilms than wild-type KLH11. AHLs and the ssaI transcript were detected in M. laxissima extracts, suggesting that AHL signalling contributes to the decision between motility and sessility and that it may also facilitate acclimation to different environments that include the sponge host.