Simple Summary
Vibrio mediterranei is associated with vibriosis in cultured bivalves, yet how environmental conditions govern its virulence remains unrevealed. We compared the pathogenicity of V. mediterranei strains toward razor clam (Sinonovacula constricta) juveniles after growth in 2216E and TCBS media. TCBS-grown bacteria caused up to 98.9% juvenile mortality, whereas 2216E-grown bacteria induced less mortality. Profiling of extracellular proteins identified 646 and 399 differentially expressed proteins in DT07 and DT02, with enrichment in secretion-related and cell envelope processes and in the two-component system, and in the two-component system, while RNA sequencing revealed 3276 and 2084 differentially expressed genes, dominated by carbon metabolism, flagellar assembly, membrane transport, and signal transduction. Linking both datasets through KEGG Orthology identifiers pointed to the two-component system (ko02020) as the most prominently represented shared pathway, with fliC, tolC and crp coupling transcriptional change to extracellular protein abundance. These results indicate that medium composition shifts the virulence of V. mediterranei in association with two-component signaling, associated with motility, extracellular protein abundance, and metabolic adaptation, and provides a candidate target for functional validation in bivalve aquaculture.
Abstract
Vibrio mediterranei is an emerging pathogen causing vibriosis outbreaks in marine bivalves, yet the molecular mechanisms by which environmental conditions modulate its virulence remain poorly understood. Here, we combined in vivo infection assays with integrated transcriptomic and extracellular products (ECPs) proteomic analyses to dissect how culture medium composition shapes the virulence of V. mediterranei toward razor clam (Sinonovacula constricta) juveniles. All tested strains caused markedly elevated juvenile mortality when cultured in TCBS medium (up to 98.9%, p < 0.0001), whereas strains grown in 2216E caused low mortality (0–3.3%), and no mortalities were recorded in the bacteria-free seawater control. Comparative ECPs proteomics identified 646 and 399 differentially expressed proteins (DEPs) in DT07 and DT02, respectively, enriched in cell envelope-related processes and in the composition of the extracellular protein fraction, the two-component system (TCS), and oxidative pathways, while transcriptomics revealed 3276 and 2084 differentially expressed genes (DEGs) dominated by carbon and energy metabolism, flagellar assembly, membrane transport, and signal transduction. Cross-omics integration via KEGG Orthology identifiers identified that the TCS (ko02020) was among the most prominent pathways linking the transcriptomic and ECPs proteomic layers, with glnA, pstS, crp, fliC, and tolC detected at both levels. fliC, tolC and crp were consistently detected at both two layers, linking transcriptional reprogramming to extracellular protein abundance. These findings implicated two-component signaling in the increased virulence of V. mediterranei in TCBS medium associated with motility, extracellular abundance, and metabolic adaptation, providing a framework for hypothesis-driven validation linking environmental cues to pathogenic potential in shellfish-associated Vibrios.