The role of RsmA in the regulation of swarming motility in Serratia marcescens

Swarming motility is a multicellular phenomenon comprising population migra tion across surfaces by specially differentiated cells. In Serratia marcesc ens, a network exists in which the flhDC flagellar regulatory master operon , temperature, nutrient status, and quorum sensing all contribute to the re gulation of swarming motility, In this study, the rsmA (repressor of second ary metabolites) gene thereafter rsmA(Sm)) was cloned from S. marcescens. T he presence of multicopy, plasmid-encoded rsmA(Sm) expressed from its nativ e promoter in S, marcescens inhibits swarming. Synthesis of N-acyl homoseri ne lactones, presumably by the product of smal (a luxl homolog isolated fro m S, marcescens), was also inhibited. Knockout of rsmA(Sm) on the S. marces cens chromosome shortens the time before swarming motility begins after ino culation to an agar surface. A single copy of the chromosomal PrsmA(Sm)::lu xAB reporter of rsmA(Sm), transcription was constructed. Using this reporte r, the roles of the flhDC flagellar regulatory master operon, temperature a nd autoregulation in the control of rsmA(Sm) expression were determined. Ou r findings indicate that RsmA(Sm) is a component of the complex regulatory network that controls swarming, Copyright (C) 2001 National Science Council , ROC and S. Karger AG, Basel.