Differential localization and bacteriostasis of Vibrio campbellii among tissues of the Eastern oyster, Crassostrea virginica

In bivalve mollusks the roles of individual tissues in antimicrobial defense remain unclear. In this study, Crassostrea virginica were injected in the adductor muscle with 105 live Vibrio campbellii. Major tissues were dissected at 10, 30, 60 or 120 min postinjection (PI); in each tissue undegraded (intact) bacteria were quantified by real-time PCR and culturable bacteria were enumerated by selective plating. At 10 min PI, accumulation of bacteria varied among tissues from approximately 2.4 × 103 (labial palps, digestive gland) to 24.2 × 103 (gonads) intact Vibrio g−1. Neither distribution nor accumulation of intact bacteria changed with time except in the hemolymph. In most tissues, more than 80% of intact bacteria were culturable at 10 min PI and culturability decreased with time. In contrast, only 19% of intact bacteria in gonadal tissue could be cultured at 10 min PI, pointing to a major role for the gonadal tissues in antibacterial defense of molluscs.