Distribution and genetic diversity of genes involved in quorum sensing and prodigiosin biosynthesis in the complete genome sequences of serratia marcescens

Abstract

Quorum sensing is a cell density-dependent regulation of gene expression. N-acyl-L-homoserine lactone (AHL) is a major quorumsensing signaling molecule in gram-negative bacteria and synthesized by the LuxI family protein. The genus Serratia is known as a producer of the red pigment, prodigiosin, whose biosynthesis is dependent on the pig gene cluster. Some Serratia strains regulate prodigiosin production viaAHL-mediated quorumsensing,whereas there is red-pigmented Serratia strainswithout quorum-sensing system. Inaddition, nonpigmentedSerratiamarcescens,whichdoes not produceprodigiosin,has alsobeenisolatedfromnatural and clinical environments. In this study, we aim to reveal the distribution and genetic diversity of quorum-sensing genes and pig gene cluster in the complete genome sequences of S. marcescens. We previously demonstrated that S. marcescens AS-1 regulates the productionof prodigiosin viaAHL-mediatedquorumsensing.We sequencedthegenomes ofAS-1andcomparedwith the complete genomes of AS-1 and the other 34 strains of S. marcescens. The luxI homologwas present on 25 complete genome sequences. The deducedamino acid sequences of the luxI homologwere dividedinto three phylogenetic classes. Incontrast, the pig gene clusterwas present in the genome of seven S.marcescens strains and only two strains, AS-1 and N4-5 contained both the luxI homolog and pig gene cluster in their genome. It is therefore assumed that prodigiosin production and its regulation by quorum sensing are not essential for the life cycle of S. marcescens.