A regulatory hydrogenase gene cluster observed in the thioautotrophic symbiont of Bathymodiolus mussel in the East Pacific Rise

Abstract

The mytilid mussel Bathymodiolus thermophilus lives in the deep-sea hydrothermal vent regions due to its relationship with chemosynthetic symbiotic bacteria. It is well established that symbionts reside in the gill bacteriocytes of the mussel and can utilize hydrogen sulfide, methane, and hydrogen from the surrounding environment. However, it is observed that some mussel symbionts either possess or lack genes for hydrogen metabolism within the single-ribotype population and host mussel species level. Here, we found a hydrogenase cluster consisting of additional H2-sensing hydrogenase subunits in a complete genome of B. thermophilus symbiont sampled from an individual mussel from the East Pacific Rise (EPR9N). Also, we found methylated regions sparsely distributed throughout the EPR9N genome, mainly in the transposase regions and densely present in the rRNA gene regions. CRISPR diversity analysis confirmed that this genome originated from a single symbiont strain. Furthermore, from the comparative analysis, we observed variation in genome size, gene content, and genome re-arrangements across individual hosts suggesting multiple symbiont strains can associate with B. thermophilus. The ability to acquire locally adaptive various symbiotic strains may serve as an effective mechanism for successfully colonizing different chemosynthetic environments across the global oceans by host mussels.

Scallop-bacteria symbiosis from the deep sea reveals strong genomic coupling in the absence of cellular integration

“…puteoserpentis , and B . thermophilus ) inhabiting vents encode hydrogenases [ 74 , 86 , 87 ], whereas seep-dwelling clam Thyasira sp. and tubeworm S. annulatum lack these genes [ 6 , 24 ].…”

Insights into phage-bacteria interaction in cold seep Gigantidas platifrons through metagenomics and transcriptome analyses

“…Investigations from seven cold seep sediment sites have reported a broad range of archaeal and bacterial viruses, such as those for Bathyarchaeota, Methanomicrobia, Thaumarchaeota, Bipolaricaulota, Coatesbacteria, and Sumerlaeota 14 . Additionally, viruses of the Myoviridae, Siphoviridae, Podoviridae, and Microviridae families have been observed in various invertebrates, such as tube worms, sponges, and mussels 13 , 22 – 24 . These viruses serve as key agents in natural ecosystems through a range of interactions with their microbial hosts.…”