Meeting Abstract

29.4  Wednesday, Jan. 5  Characterization of the Bacterial Properties that Impair Respiration in the Atlantic Blue Crab, Callinectes sapidus JOHNSON, N.G.*; BURNETT, L.E.; BURNETT, K.G.; College of Charleston; College of Charleston; College of Charleston ngjohnso@edisto.cofc.edu

In the blue crab Callinectes sapidus, injection with the bacterial pathogen Vibrio campbellii causes a decrease in oxygen consumption. Histological and physiological evidence suggests that the physical obstruction of hemolymph flow through the gill vasculature, caused by aggregations of bacteria and hemocytes, underlies the decrease in aerobic function associated with bacterial infection. We sought to elucidate the bacterial properties sufficient to induce a decrease in circulating hemocytes, reflecting hemocyte aggregation and decreased respiration. Lipopolysaccharide (LPS), the primary component of the Gram negative bacterial cell wall, is known to interact with crustacean hemocytes. Purified LPS was covalently bound to the surfaces of polystyrene beads, resembling bacteria in size. Injection of these “LPS beads” caused a decrease in circulating hemocytes comparable to that seen with V. campbellii injection, while beads alone failed to do so. These data suggest that a wide range of Gram negative bacteria could stimulate hemocyte aggregation. To test this hypothesis, crabs were injected with different bacterial species—six Gram negatives and one Gram positive—and their effects on circulating hemocytes were assessed. With one exception, all Gram negatives caused decreases in circulating hemocytes. Differences could be explained by variation in structure and content of LPS across bacterial species. However, LPS is not necessary to provoke the immune response, as Bacillus coral, which lacks LPS, caused a decrease in circulating hemocytes. To better understand the metabolic costs of mounting an immune response, future studies will explore the relationship between hemocyte aggregation and respiration. (NSF IOS-0725245)