Identification of a c-di-GMP-Regulated Polysaccharide Locus Governing Stress Resistance and Biofilm and Rugose Colony Formation in Vibrio vulnificus

Abstract

As an etiological agent of bacterial sepsis and wound infections, Vibrio vulnificus is unique among the Vibrionaceae. Its continued environmental persistence and transmission are bolstered by its ability to colonize shellfish, form biofilms on various marine biotic surfaces, and generate a morphologically and physiologically distinct rugose (R) variant that yields profuse biofilms. Here, we identify a c-di-GMP-regulated locus (brp, for biofilm and rugose polysaccharide) and two transcription factors (BrpR and BrpT) that regulate these physiological responses. Disruption of glycosyltransferases within the locus or either regulator abated the inducing effect of c-di-GMP on biofilm formation, rugosity, and stress resistance. The same lesions, or depletion of intracellular c-di-GMP levels, abrogated these phenotypes in the R variant. The parental and brp mutant strains formed only scant monolayers on glass surfaces and oyster shells, and although the R variant formed expansive biofilms, these were of limited depth. Dramatic vertical expansion of the biofilm structure was observed in the parental strain and R variant, but not the brp mutants, when intracellular c-di-GMP levels were elevated. Hence, the brp-encoded polysaccharide is important for surface colonization and stress resistance in V. vulnificus, and its expression may control how the bacteria switch from a planktonic lifestyle to colonizing shellfish to invading human tissue.

Capsular polysaccharide production and serum survival of Vibrio vulnificus are dependent on antitermination control by RfaH

“…There is at least one additional target of RfaH in V. vulnificus as an ops element was also identified within the brp operon . This set of genes encodes functions required for rugosity and production of the exopolysaccharide associated with rugose cells, and transcription of the brp genes was found to be highly up‐regulated in rugose compared to opaque and translucent variants . Eventual characterization of RfaH control of rugosity in V. vulnificus would require construction of an rfaH mutant beginning with a rugose parent rather than the opaque one used here and assessment of the effects of this defect on brp operon transcription and rugose exopolysaccharide production.…”

LuxR Homologue SmcR Is Essential for Vibrio vulnificus Pathogenesis and Biofilm Detachment, and Its Expression is Induced by Host Cells

“…There are several lines of evidence supporting the idea that V. vulnificus bacteria embed themselves in oyster tissues and form biofilms to colonize and to persist in oysters as a primary infection route of the pathogen (46,47). Recently, scanning electron microscopy analysis revealed V. vulnificus biofilm structures formed on oyster shells (48). Therefore, the data obtained in this study in which biofilms rather than planktonic cells were used in mouse infection experiments could be more realistic and reliable ( Fig.…”

Genome Sequence of the Human-Pathogenic Bacterium Vibrio vulnificus Type Strain ATCC 27562

“…These genes have long been reported by many research papers (1,9,15). Overall, as this strain has long been used in the labs all over the world, the genome sequence of Vibrio vulnificus ATCC 27562 T provides an excellent foundation for disease control and comparative and basic research.…”