Meeting Abstract

P3.186  Friday, Jan. 6  Bacterial endosymbionts in the gorgonian Leptogorgia virgulata and their potential role in spicule formation. KINGSLEY, R.J.*; ARMISTEAD, B.E; HOOPER, C.W.; OSZUSTOWICZ, A.L.; PALMER, A.D.; University of Richmond, Richmond VA; University of Richmond, Richmond VA; University of Richmond, Richmond VA; University of Richmond, Richmond VA; University of Richmond, Richmond VA rkingsle@richmond.edu

Leptogorgia virgulata is a gorgonian species lacking endosymbiotic zooxanthellae. Their possible relationship with symbiotic bacteria however, has not been previously studied. We are particularly interested in urease-producing bacteria, which could be involved in a pH regulatory mechanism in the calcifying tissues of L. virgulata. Like all calcifying systems, calcium carbonate spicule formation in L. virgulata causes a drop in pH, which must be quickly neutralized to prevent decalcification. We propose that bacterial urease catalyzes the hydrolysis of urea to ammonia and carbon dioxide. The subsequent formation of ammonium and bicarbonate ions would rapidly raise the pH, sustaining spicule formation. DGGE analysis shows a highly diverse microbial community within L. virgulata. The community structure varies depending on the different tissue types. Sequencing data illustrates the presence of at least one urease-producing strain of bacteria living in the L. virgulata tissue. Scanning electron microscopy also reveals the presence of bacteria in tissues. Preliminary stable isotope data indicates that bacteria are not a source of nutrition however; nitrogenous products appear to be transferred from bacteria to gorgonian host. These findings support our hypothesis that L. virgulata harbors endosymbiotic bacteria that may be involved in spicule calcification.