The RssAB Regulation Controlling Serratia Marcescens Swarming, Biofilm Formation and Pathogenesis

A model on the molecular mechanism of regulation of multicellular behavior such as swarming, sliding, biofilm formation and pathogenesis in Serratia marcescens has been established. Components identified to be involved in such regulatory network include a RssB-RssA two-component signal transduction system, a FlhDC master operon regulatory system, a SpnI/R quorum-sensing system, RsmA global inhibitory protein, a mobile transposon TnTIR carrying the spnIR genes, a dapA-nlpA genetic locus specifically regulating cell morphogenesis and swarming respectively, and a functionally unknown SpnT inhibiting sliding and chromosomal DNA resolution. At the same time, regulation of prodigiosin (an antibiotic derivative, a pigment and an immunosuppressive agent), phospholipase and nuclease production is also coordinately regulated by RssB-RssA. We also showed that ygfF, flhDC, shlBA, rssB and other related genes involving motility regulation, synthesis of hemolysin, LPS-synthesis, rssB-rssA expression, and one cyoA gene are under the control of RssB-RssA. The regulation of RssB-RssA by saturated fatty acids and the corresponding biochemical phosphorelay reaction are confirmed. Using modified CHIP(chromosome immuno-precipitation) and EMSA(electrophoresis mobility shift assay), we have preliminarily identified around 60 genes under direct control of RssB-RssA. To further build on our findings to describe new aspects of the regulatory mechanisms that underlie regulation of virulence, biofilm formation and swarming/sliding, we will continue to characterize the upstream signals activating RssB-RssA, the conformational change after activation and the downstream RssB-RssA regulon, linking their relationship to swarming, biofilm formation and pathogenesis.

Project ID:PC9808-0567
External Project ID:NSC98-2320-B182-007-MY3