A dual symbiosis shared by two mussel species, Bathymodiolus azoricus and Bathymodiolus puteoserpentis (Bivalvia: Mytilidae), from hydrothermal vents along the northern Mid‐Atlantic Ridge

Abstract

Bathymodiolus azoricus and Bathymodiolus puteoserpentis are symbiont-bearing mussels that dominate hydrothermal vent sites along the northern Mid-Atlantic Ridge (MAR). Both species live in symbiosis with two physiologically and phylogenetically distinct Gammaproteobacteria: a sulfur-oxidizing chemoautotroph and a methane-oxidizer. A detailed analysis of mussels collected from four MAR vent sites (Menez Gwen, Lucky Strike, Rainbow, and Logatchev) using comparative 16S rRNA sequence analysis and fluorescence in situ hybridization (FISH) showed that the two mussel species share highly similar to identical symbiont phylotypes. FISH observations of symbiont distribution and relative abundances showed no obvious differences between the two host species. In contrast, distinct differences in relative symbiont abundances were observed between mussels from different sites, indicating that vent chemistry may influence the relative abundance of thiotrophs and methanotrophs in these dual symbioses.

Evidence for hydrogen oxidation and metabolic plasticity in widespread deep-sea sulfur-oxidizing bacteria

“…Our analyses also show that these two SUP05 lineages cluster closely with all previously identified SUP05 populations and fall into two cooccurring distinct subclades, similar to sequences retrieved from the African Shelf Namibian Upwelling zone and from the Saanich Inlet OMZ. The closest relatives of the GB SUP05 are the SUP05 SI-1 lineage (GB-1) (9) and symbionts of Bathymodiolus mussels from hydrothermal vents (GB-2) (23,24). High-throughput sequencing of the SSU rRNA gene amplicons from the GB water column indicate that GB-1 and -2 dominate the deep waters of the GB (>1,700 m), comprising up to 30% of the microbial community (Fig.…”

Molecular evidence of digestion and absorption of epibiotic bacterial community by deep-sea crab Shinkaia crosnieri

“…The hydrothermal vent mussels Bathymodiolus azoricus and B. puteoserpentis are nutritionally sustained by chemolithoautotrophic and methanotrophic endosymbionts (Duperron et al, 2006;Petersen et al, 2011). When 13 C enrichment was evaluated in 13 C-labelled bicarbonate tracer experiments using living B. azoricus individuals, the 13 C enrichment level in the gill containing thioautotrophic endosymbionts was the highest among all tissues, whereas the 13 C enrichment level of tissues, including the digestive system, was slightly higher compared with that of muscles (Riou et al, 2008).…”

Influence of CH<sub>4</sub> and H<sub>2</sub>S availability on symbiont distribution, carbon assimilation and transfer in the dual symbiotic vent mussel <i>Bathymodiolus azoricus</i>

“…Phylogenetic analyses show that the two Mytilid species share the same 16S rRNA phylotype of sulphide-oxidizing γ -proteobacteria, but harbour two distinct strains (Won et al, 2003). Duperron et al (2006) found that the MOB 16S rRNA phylotype was also shared between the two mussel species, and that vent chemistry could affect the relative abundance of SOB and MOB. The volume occupied by each type of symbiont present within V. Riou et al: Bathymodiolus azoricus' carbon fixation by chemosynthesis a bacteriocyte, quantified using 3D fluorescence in situ hybridization (FISH) technique, varies from vent site to vent site between B. azoricus specimens (Halary et al, 2008).…”