Biogenesis of outer membrane vesicles in Serratia marcescens is thermoregulated and can be induced by activation of the Rcs phosphorelay system

MCMAHON, KENNETH J. ; CASTELLI, MARÍA EUGENIA; GARCÍA VÉSCOVI, ELEONORA; FELDMAN, MARIO

JOURNAL OF BACTERIOLOGY

AMER SOC MICROBIOLOGY

Año: 2012

0021-9193

Outer membrane vesicles (OMVs) have been identified in a wide range of bacteria, yet little isknown of their biogenesis. It has been proposed that OMVs can act as long range toxin deliveryvectors and as a novel stress response. We have found that the formation of outer membranevesicles in the Gram negative opportunistic pathogen Serratia marcescens is thermoregulated,with a significant amount of OMVs produced at 22 or 30 oC, and negligible quantities formed at37 oC under laboratory conditions. Inactivation of the synthesis of the enterobacterial commonantigen (ECA) resulted in a hyper-vesiculation phenotype, supporting the hypothesis that OMVsare produced in response to stress. We demonstrate that the phenotype can be reversed to WTlevels upon the loss of the Rcs-phosphorelay response regulator RcsB, but not RcsA, suggestinga role for the Rcs-phosphorelay in the production of OMVs. MS-fingerprinting of the OMVprovided evidence of cargo selection within wild-type cells suggesting a possible role of SerratiaOMV in toxin delivery. In addition, OMV associated cargo proved toxic upon injection into thehaemocoel of Galleria melonella larvae. These experiments demonstrate that OMV are theresult of a regulated process in Serratia and suggest that OMV could play a role in virulence.