A trigger phosphodiesterase modulates the global c-di-GMP pool, motility and biofilm formation in Vibrio parahaemolyticus.

Abstract

Vibrio parahaemolyticus cells transit from free swimming to surface adapted lifestyles, such as swarming colonies and three-dimensional biofilms. These transitions are regulated by sensory modules and regulatory networks that involve the second messenger cyclic dimeric guanosine monophosphate (c-di-GMP). In this work, we show that a previously uncharacterized c-di-GMP phosphodiesterase (VP1881) from V. parahaemolyticus plays an important role in modulating the c-di-GMP pool. We found that the product of VP1881 promotes its own expression when the levels of c-di-GMP were low or when the phosphodiesterase was catalytically inactive. This behavior has been observed in a class of c-di-GMP receptors called Trigger phosphodiesterases, hence we named the product of VP1881 TpdA, for Trigger phosphodiesterase A. The absence of tpdA showed a negative effect on swimming motility while its overexpression from an IPTG inducible promoter showed a positive effect on both swimming and swarming motility, and a negative effect on biofilm formation. Changes in TpdA abundance altered the expression of representative polar and lateral flagellar genes as well as the biofilm related gene cpsA. Our results also revealed that autoactivation of the native PtpdA promoter is sufficient to alter c-di-GMP signaling responses such as swarming and biofilm formation in V. parahaemolyticus, an observation that could have important implications in the dynamics of this social behaviors. ImportanceC-di-GMP trigger phosphodiesterases (PDEs) could play a key role in controlling the heterogeneity of biofilm-matrix composition, a property that endows characteristics that are potentially relevant for sustaining integrity and functionality of biofilms in a variety of natural environments. Trigger PDEs are not always easy to identify based on their sequence, hence not many examples of these type of signaling proteins have been reported in the literature. Here we report on the identification of a novel trigger PDE in V. parahaemolyticus and provide evidence suggesting that its autoactivation could play an important role in the progression of swarming motility and biofilm formation, multicellular behaviors that are important for the survival and dissemination of this environmental pathogen.