Regulatory effects of Shewanella putrefaciens isolated from shrimp Penaeus orientalis on the virulence factors of Vibrio parahaemolyticus and evaluation of the role of quorum sensing in virulence factors regulation

Abstract

As an aquatic pathogen widely present in aquatic food, Vibrio parahaemolyticus causes outbreaks of gastroenteritis across the globe. Virulence factors of V. parahaemolyticus increases with the amount of spoilage in aquatic organisms including shrimp, but mechanisms regulating its virulence factors are not well understood. In this study, five spoilage bacterial isolated from shrimp were investigated for their regulatory effects on the virulence factors including hemolysin and biofilm of V. parahaemolyticus. Among these isolates, Shewanella putrefaciens induced hemolytic activity in V. parahaemolyticus in a time-dose-temperature- dependent manner and we found the main component responsible for this effect to be the supernatant or cell free extract of S. putrefaciens. Total hemolytic activity, expression of the thermostable direct hemolysin gene tdh, and biofilm production of V. parahaemolyticus were significantly up-regulated by S. putrefaciens, but also by deletion of quorum-sensing luxM or luxS gene of V. parahaemolyticus. However, this regulation by S. putrefaciens was significantly impaired by deletion of luxM gene. but not by deletion of the luxS gene. Further study showed S. putrefaciens exhibited a strong degradation ability on signaling molecule AHL synthesized by the luxM enzyme. This study revealed a novel virulence regulatory mechanism that S. putrefaciens can significantly increases the virulence factors of V. parahaemolyticus via interfering luxM type quorum-sensing signaling pathway through its AHL-degradation ability.

https://ift.tt/2J4gaHe