luxS mutants of Serratia defective in autoinducer-2-dependent ‘quorum sensing’ show strain-dependent impacts on virulence and production of carbapenem and prodigiosin

Abstract

The enzyme LuxS is responsible for the production of autoinducer-2 (AI-2), a molecule that has been implicated in quorum sensing in many bacterial species. This study investigated whether there is a luxS-dependent signalling system in the Gram-negative bacteria Serratia spp. Serratia marcescens is a broad-host-range pathogen and an important cause of nosocomial infections. Production of AI-2 activity was detected in S. marcescens ATCC 274 and Serratia ATCC 39006 and their luxS genes were sequenced. luxS mutants were constructed in these strains and were analysed to determine which phenotypes are regulated by luxS and therefore, potentially, by AI-2. The phenotypes of the luxS mutants included decreased carbapenem antibiotic production in Serratia ATCC 39006 and decreased prodigiosin and secreted haemolysin production in S. marcescens ATCC 274. The luxS mutant of S. marcescens ATCC 274 was also found to exhibit modestly reduced virulence in a Caenorhabditis elegans model. Finally, it was shown that the culture supernatant of a wild-type strain contains a signal, presumably AI-2, capable of complementing the prodigiosin defect of the luxS mutant of another strain, even when substantially diluted. It is concluded that luxS modulates virulence and antibiotic production in Serratia, in a strain-dependent manner, and that, for at least one phenotype, this regulation is via extracellular signalling.

The Serratia gene cluster encoding biosynthesis of the red antibiotic, prodigiosin, shows species- and strain-dependent genome context variation

“…Sma 274 has been tested for production of AHLs and the presence of smaI/R homologues (data not shown), and no AHL-dependent quorum-sensing system has been detected (data not shown). Recently, luxS, which is responsible for the production of Autoinducer-2 (AI-2), has been shown to regulate prodigiosin production via extracellular signalling in Sma 274 (Coulthurst et al, 2004). No evidence of an AHL-dependent quorum-sensing system controlling pigment biosynthesis has been found in any of the other 22 S. marcescens strains tested, of which seven are pigmented (data not shown), implying that quorum-sensing control of prodigiosin production is both highly strain dependent and comparatively rare.…”

The stationary phase sigma factor, RpoS, regulates the production of a carbapenem antibiotic, a bioactive prodigiosin and virulence in the enterobacterial pathogen Serratia sp. ATCC 39006

“…S39006 also produces the plant cell wall-degrading exoenzymes pectate lyase and cellulase, which contribute to potato rot (Crow, 2001;Slater et al, 2003). It demonstrates a broad-host-range capacity for pathogenesis and is virulent in the animal Caenorhabditis elegans (Coulthurst et al, 2004).…”

Overproduction of individual gas vesicle proteins perturbs flotation, antibiotic production and cell division in the enterobacterium Serratia sp. ATCC 39006

“…Prodiginines have anticancer, immunosuppressant and antimalarial properties and are of interest due to their pro-apoptotic activities (Hsieh et al, 2012;Marchal et al, 2014;Espona-Fiedler et al, 2012;Lu et al, 2012;Liu et al, 2013). S39006 is also a plant pathogen that produces plant cell wall degrading enzymes such as pectinases and cellulases (Fineran et al, 2005(Fineran et al, , 2007 but is also capable of killing the nematode worm Caenorhabditis elegans (Coulthurst et al, 2004;Wilf et al, 2011). Many of these phenotypes, including production of gas vesicles, are regulated in a manner dependent on cell concentration through the SmaIR quorum sensing system (Fineran et al, 2005;Ramsay et al, 2011).…”