Detection of virulence factors and quorum sensing signal molecules of aquatic bacteria from Yellow River carp

Abstract:

[Background] Aquatic pathogens restrict the healthy development of aquaculture; quorum sensing is closely related to the production of virulence factors. The characteristics of virulence factors regulated by quorum sensing is worthy of further study. [Objective] To explore the relationship between quorum sensing and bacterial diseases of Yellow River carp, and clarify the influence of quorum sensing on the characteristics of virulence factors. [Methods] The 16S rRNA gene was sequenced and the phylogenetic tree was constructed to determine the evolutionary status of the selected strains. The activity of extracellular protease was detected by skim milk plate method and azo casein method. The bacterial biofilm forming ability was determined by crystal violet staining. The producing ability of AI-2 and AHLs was determined by reporter strain BB170 and CV026, respectively. The effects of exogenous HSLs on extracellular protease ability and biofilm formation ability were detected. [Results] Hafnia sp. Z11 and Aeromonas sp. Z12 were evidenced with high levels of extracellular protease activity and biofilm formation ability, and could secrete AHLs signal molecules, which were density dependent. High concentration of C4-HSL and C6-HSL could increase the extracellular protease activity and biofilm formation activity of strain Z11 and Z12, respectively. [Conclusion] High concentration of quorum sensing factors (AHLs) can promote the extracellular protease activity of Hafnia sp. Z11 and Aeromonas sp. Z12, suggesting that the quorum sensing of these two bacteria may affect their virulence.