Bacterial warfare at the molecular level: Pseudoalteromonas sp. H2 disrupts Vibrio splendidus membrane integrity via ClpP-CheW2 regulation

Abstract

In mariculture ecosystems where Vibrio spp. are predominant pathogens, effective biocontrol through antagonistic probiotics remains an unresolved biological challenge. Here, the Pseudoalteromonas sp. H2 strain was first determined to inhibit Vibrio splendidus AJ01 growth through contact-dependent antagonism. Integrated analysis of ΔcheW2 differentially expressed genes and experimental validation confirmed that the coupling protein CheW2 negatively regulates outer membrane protein-encoding genes. The results of antagonism assays demonstrated that the chemotaxis protein CheW2 in V. splendidus AJ01 partially affected the antagonistic activity of Pseudoalteromonas sp. H2. Dual RNA-seq analysis during coculture revealed physiological/metabolic and transcriptional shifts in both bacteria. The results of in vivo and in vitro experiments confirmed that the serine protease ClpP regulated CheW2 protein levels through protein degradation, establishing a ClpP-CheW2 axis for regulating membrane integrity in V. splendidus AJ01. Crucially, the above results of dual RNA-seq analysis and experiments with the reporter strains constructed by the fusion of the ClpP promoter to the gfp gene revealed that coculture with Pseudoalteromonas sp. H2 attenuated the expression of clpP gene in V. splendidus AJ01. Taken together, these findings revealed a novel antagonistic strategy in which antagonistic bacteria manipulate gene expression in their competitor to facilitate a competitive advantage, providing new insights into niche adaptation.