Vibrio parahaemolyticus outer membrane porin Vpa0810 regulates its biofilm formation and plays a vital role in its stresses tolerance.

Vibrio parahaemolyticus (V. parahaemolyticus), a Gram-negative halophilic bacterium, is a leading seafood-borne pathogen that can cause acute gastroenteritis. Outer membrane (OM) porins are involved in exporting extracellular polymeric substances, which is essential for biofilm formation. However, the contribution of porins to the biofilm formation of V. parahaemolyticus is still obscure. We recently found that a mutation in the DHH/DHHA1 family gene vp2835 enhances biofilm formation in V. parahaemolyticus but inhibits its motility. Here, we identified an OM porin gene, vpa0810, from Δvp2835 strain. The deletion of vpa0810 in the wild type strain resulted in the inhibition of both swarming and swimming motility, while reverted the motility defect of Δvp2835. The Δvpa0810 decreased its biofilm formation capability in both the wild type and the Δvp2835 strain. Additionally, the surface hydrophobicity, auto-aggregation, OM permeability, and exopolysaccharides (EPS) content were decreased in the Δvpa0810 strain. Interestingly, qRT-PCR results demonstrated that the genes involved in EPS synthesis (cpsA, scvE, and cpsF) and the porin gene ompW were significantly up-regulated in the Δvpa0810 strain, but down-regulated in the Δvp2835-Δvpa0810 double mutant. Furthermore, the deletion of vpa0810 compromised its ability to form biofilm on silicon wafers, glass, stainless-steel plates, as well as on shrimp and crab surfaces. The vpa0810 deletion mutation also reduced its stress tolerance to bile salt, low pH, low temperature, and the antibiotics colistin. In summary, our data suggest that Vpa0810 may regulate biofilm formation through EPS biosynthesis and exportation, which might provide a new target for developing control strategies against V. parahaemolyticus.