Environmental availability of Lucinid symbionts

Loripes orbiculatus, a member of the species-rich chemosymbiotic bivalve family Lucinidae, can be found throughout the Mediterranean and has a well-studied environmentally-acquired symbiont population of Ca. Thiodiazotropha symbionts.We used 16S rRNA gene amplicon surveys to search for such reservoirs near L. orbiculatus within the Mediterranean. We report low relative abundance of Ca. Thiodiazotropha in an environmental setting, with mucus tubes formed by L. orbiculatus, and seagrass samples having higher abundance than background pore water and sediment samples. We also report that L. orbiculatus releases significant symbiont gene copies under certain experimental conditions. This research reinforces the significance of both seagrass and lucinids in their role in the Lucinid symbiont acquisition and life cycle. Sequencing was performed at the Joint Microbiome Facility of the Medical University of Vienna and the University of Vienna under the project IDs JMF-1902-4 and JMF-2001-3.