Identification of Mcp14320 as an L-aspartate chemoreceptor in marine pathogen Vibrio splendidus

Background Bacterial chemotaxis contributes to diverse physiological processes including nutrient acquisition, environmental sensing, and host–pathogen interactions, but the specific roles of individual chemoreceptors in mediating chemotaxis in Vibrio species remain incompletely characterized. Methods We identified and characterized Mcp14320, a putative TarH-type four-helix bundle (4HB) chemoreceptor in the marine pathogen Vibrio splendidus AJ01, using bioinformatic analysis, in-frame gene deletion, capillary and soft-agar gradient chemotaxis assays, recombinant expression and purification of its ligand-binding domain (rMcp14320-LBD), in vitro amino acid binding assays, and artificial infection of Manila clams ( Ruditapes philippinarum ) via adductor muscle injection. Results Bioinformatic analysis revealed that Mcp14320 possesses an N-terminal TarH ligand-binding domain with a 4HB fold. Deletion of mcp14320 abolished chemotaxis toward L-aspartate without affecting responses to the other 19 amino acids tested, and rMcp14320-LBD specifically bound L-aspartate in vitro . The mcp14320 deletion mutant exhibited no significant virulence attenuation compared with the wild-type strain ( P = 0.546). Conclusion The present results establish Mcp14320 as the first TarH-type 4HB chemoreceptor functionally characterized in a marine Vibrio species that mediates specific chemotaxis toward L-aspartate.