Interaction of the Pathogen Gaffkya homari with Natural Defense Mechanisms of Homarus americanus

Abstract

Infection of the lobster Homarus americanus with the bacterium Gaffkya homari invariably proved fatal. Very small numbers of this pathogen introduced into the hemolymph resulted in septicemia and death, i.e., a dose level as low as approximately five bacteria per lobster at a temperature of 15 C was sufficient to kill 90% of the lobsters in 17 days. The mean time to death was virtually constant, regardless of the dose, indicating a general lack of host defense against G. homari.Investigation of the interaction of G. homari with the defense factors apparent in lobster hemolymph (bactericidal, agglutinin, and phagocytic activities) helped to account for its pathogenicity. Gaffkya homari was unique among the microorganisms tested in that (1) it was resistant to the agglutinin (s); (2) its growth was stimulated by the hemolymph serum rather than inhibited or unaffected; (3) although it was phagocytized, the bacterium could overcome this effect and multiply in the hemolymph.