Mutational analysis of flagellum-independent surface spreading of Serratia marcescens 274 on a low-agar medium

Abstract

In a previous study (J. O'Rear, L. Alberti, and R. M. Harshey, J. Bacteriol. 174:6125-6137, 1992) we reported the isolation of several transposon mutants of Serratia marcescens 274 that were defective either in swarming alone or in both swimming and swarming motility. All the nonflagellate (Fla ؊ ) mutants, while defective in both types of motility, were able to spread rapidly on the surface of low-agar (0.35%) media. We show here that some of the swarming-defective mutants are defective in the production of serrawettin W1, an extracellular cyclic lipopeptide produced by S. marcescens 274. When combined with a Fla defect, the serrawettin (Swt) mutants are deficient in spreading on low-agar media. The spreading deficiency can be overcome by serrawettin supplied extracellularly. Introduction of Fla defects into chemotaxis mutants does not affect this mode of surface translocation. These results suggest that spreading may be a passive form of translocation. We also report that swarming defects in all mutants showing a Dps phenotype (able to swarm within the inoculated area but unable to move outward) in the earlier study can be overcome by changing the commercial source of agar.Serratia marcescens is a pigmented enteric bacterium found in variety of niches, which include soil, water, air, plants, and animals (9). It is also an opportunistic human pathogen, causing many nosocomial infections (7). S. marcescens is unique among enteric bacteria in many respects. It secretes extracellular chitinases, several proteases, a nuclease, and a lipase (13) and produces a wetting agent or surfactant called serrawettin, which helps in the colonization of surfaces (14,15,17). In keeping with its varied habitat, S. marcescens produces alternate forms of differentially flagellated cells which display different types of motility depending on whether the growth medium is liquid or solid (2). Nonflagellated cells of S. marcescens can also translocate (spread) efficiently over the surface of low-agar media (20).Surface colonization via swarming requires the flagellar apparatus as well the chemotaxis system (20). A large-scale transposon mutagenesis study of S. marcescens identified several additional functions that were needed for swarming (20). A sizable subset of the mutants showed a Dps phenotype (cells were capable of swarming but remained confined to the inoculated area, i.e., were unable to move outwards). A distinct group of the Dps mutants (DpsI) appeared not to produce the extracellular slime layer generally visible around the bacterial colony. We show here that some of the DpsI mutants as well as some Dis (completely defective in swarming) mutants are defective in the production of serrawettin W1, an extracellular cyclic lipopeptide (14, 24). Flagellum-independent spreading of S. marcescens 274 on the surface of low-agar media also requires serrawettin. Defects in chemotaxis functions, however, had no effect on this mode of surface colonization. Our results reveal the importance of bacterial surface layers (serrawettins, slim...

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

“…S. marcescens has been isolated from soil, water, plants and air (Grimont & Grimont, 1978). The ability of some S. marcescens strains to colonize a wide range of ecological niches has been linked to the production of a spectrum of extracellular products including chitinases, proteases, lipases, nucleases, bacteriocins, surfactants and wetting agents (Braun & Schmitz, 1980;Clegg & Allen, 1985;Hines et al, 1988;Matsuyama et al, 1995;Yanagida et al, 1986).…”

The Rap and Hor proteins of Erwinia, Serratia and Yersinia: a novel subgroup in a growing superfamily of proteins regulating diverse physiological processes in bacterial pathogens

“…The ability of Sma to cause disease and to inhabit a wide variety of ecological niches has been linked to the production of an array of extracellular products, including proteases, chitinases, nucleases, lipases, wetting agents, bacteriocins and the bright red pigment, 2-methyl-3-pentyl-6-methoxyprodigiosin or prodigiosin (Pig; Braun and Schmitz, 1980;Clegg and Allen, 1985;Yanagida et al, 1986;Hines, 1988;Matsuyama et al, 1995).…”

Identification and Characterization of the pswP Gene Required for the Parallel Production of Prodigiosin and Serrawettin W1 in Serratia marcescens

“…Genetic analysis of parallelism in production of these exolipids indicated an essential step in PCP-dependent systems that is common to biosynthesis of prodigiosin and serrawettin W1 by S. marcescens. (6) was used routinely in the genetic experiments as described previously (16). The bacteria grown on a peptone-glycerol (PG) agar medium (15) were examined for pigment production and wetting activity (spontaneous spreading of bacterial suspension on a glass slide) as described previously (7).…”