The Translocation and Assembly Module (TAM) of Is Essential for Stress Resistance and Host Infection.

Translocation and assembly module (TAM) is a protein channel known to mediate the secretion of virulence factors during pathogen infection. is a Gram-negative bacterium that is pathogenic to a wide range of farmed fish and other hosts including humans. In this study, we examined the function of the two components of the TAM, TamA and TamB, of (named and , respectively). TamA was found to localize on the surface of and be recognizable by TamA antibody. Compared to the wild type, the and knockouts, TX01Δ and TX01Δ, respectively, were significantly reduced in motility, flagella formation, invasion into host cells, intracellular replication, dissemination in host tissues, and inducing host mortality. The lost virulence capacities of TX01Δ and TX01Δ were restored by complementation with the and genes, respectively. Furthermore, TX01Δ and TX01Δ were significantly impaired in the ability to survive under low pH and oxidizing conditions, and were unable to maintain their internal pH balance and cellular structures in acidic environments, which led to increased susceptibility to lysozyme destruction. Taken together, these results indicate that TamA and TamB are essential for the virulence of and required for to survive under stress conditions.