Unusual ultrastructure of bacterial endosymbionts in the bivalve Thyasira sarsi from Central Skagerrak

An ultrastructural investigation was made of the symbiotic bacteria in the gills of the bivalve Thyasira sarsi from the Central Skagerrak. The bacteria were characterized by sulphur globules in the periplasmic space and by peripheral intracellular membrane stacks. Apart from the membrane system they were very similar to previously described sulphur-oxidizing symbionts of the same species from Bergen, Norway. Stable carbon isotope data and lack of C1 -metabolism enzymes gave additional evidence for sulphur-oxidizing symbionts in T. sarsi in the Skagerrak, too