Interactions between different strains of Vibrio alginolyticus and hemolymph fractions from adult Mytilus edulis.

The juvenile-bivalve pathogen Vibrio alginolyticus NCMB 1339 was toxic, in vitro, to hemocytes from adult Mytilus edulis. Toxicity was mediated by both washed bacterial cells and culture supernates. Washed cells of an environmental isolate of V. alginolyticus, Strain PS-1, were 2.5 times less toxic to Mytilus hemocytes, but this strain did produce a lethal extracellular factor(s) in broth culture, albeit at lower levels than V. alginolyticus NCMB 1339. Hemolymph fractions from Mytilus exerted a reciprocal toxic effect on the bacteria. Hemocytes were responsible for most of this bacteriocidal activity and toxic oxygen intermediates were involved in the phagocytic defense mechanisms of these cells.