The host may digest the symbiont and absorb the released nutrients ( Kuwahara et al., 2007 Newton et al., 2007). magnifica revealed that they fix CO 2 via ribulose-1,5-bisphosphate carboxlase/oxygenase (RubisCO) and synthesize amino acids and other organic compounds, although no export system for these synthesized organic compounds to the host has been found ( Kuwahara et al., 2007 Newton et al., 2007). Genome analyses of symbionts of Calyptogena okutanii and C. They harbor thioautotrophic symbiotic bacteria in their gill epithelial cells and nutritionally depend on their symbionts because their digestive tracts are vestigial (Pennec et al., 1995). This indicates that the C i supply process to symbionts in the vacuole (symbiosome) in bacteriocytes is essential for symbiosis.ĭeep-sea clams belonging to the genus Calyptogena form dense communities on the deep-sea floor near hydrothermal vents and methane seeps ( Dover, 2000 Fisher, 1990). The present study showed that CA is abundant in the gill tissues of deep-sea symbiotic bivalves and specifically localizes in the cytoplasm of bacteriocytes of C. Western blot analysis and measurement of activity showed that CA was abundantly (26–72% of total soluble protein) detected in the gill tissues of not only Calyptogena clams but also deep-sea Bathymodiolus mussels that harbor thioautotrophic or methanotrophic symbiotic bacteria, but was not detected in a non-symbiotic mussel, Mytilus sp. okutanii, which showed that CA was exclusively localized in the symbiont-harboring cells (bacteriocytes) in gill epithelial cells. okutanii were used in western blot analysis and immunofluorescence staining of the gill tissues of C. Mouse monoclonal antibodies against the CA of C. okutanii, and the enzyme was purified by affinity chromatography. We found that acetazolamide-sensitive soluble CA was abundantly expressed in the gill tissue of C. We therefore analyzed mRNA sequences, proteins and CA activity in Calyptogena okutanii using expression sequence tag, SDS-PAGE and LC-MS/MS.
However, the localization of CA in gill tissue remains unknown. Carbonic anhydrase (CA) from the host catalyzes the reaction CO 2 + H 2O ↔ HCO 3 − + H +, and is assumed to facilitate inorganic carbon (C i) uptake and transport to the symbiont. The symbiont fixes CO 2 to synthesize organic compounds. Deep-sea Calyptogena clams harbor thioautotrophic intracellular symbiotic bacteria in their gill epithelial cells.
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