title: Intracellular Oceanospirillales inhabit the gills of the hydrothermal vent snail Alviniconcha with chemosynthetic, γ-Proteobacterial symbionts.
abstract: Associations between bacteria from the γ-Proteobacterial order Oceanospirillales and marine invertebrates are quite common. Members of the Oceanospirillales exhibit a diversity of interactions with their various hosts, ranging from the catabolism of complex compounds that benefit host growth to attacking and bursting host nuclei. Here, we describe the association between a novel Oceanospirillales phylotype and the hydrothermal vent snail Alviniconcha. Alviniconcha typically harbour chemoautotrophic γ- or ε-Proteobacterial symbionts inside their gill cells. Via fluorescence in situ hybridization and transmission electron microscopy, we observed an Oceanospirillales phylotype (named AOP for ‘Alviniconcha Oceanospirillales phylotype’) in membrane-bound vacuoles that were separate from the known γ- or ε-Proteobacterial symbionts. Using quantitative polymerase chain reaction, we surveyed 181 Alviniconcha hosting γ-Proteobacterial symbionts and 102 hosting ε-Proteobacterial symbionts, and found that the population size of AOP was always minor relative to the canonical symbionts (median 0.53% of the total quantified 16S rRNA genes). Additionally, we detected AOP more frequently in Alviniconcha hosting γ-Proteobacterial symbionts than in those hosting ε-Proteobacterial symbionts (96% and 5% of individuals respectively). The high incidence of AOP in γ-Proteobacteria hosting Alviniconcha implies that it could play a significant ecological role either as a host parasite or as an additional symbiont with unknown physiological capacities.
authors.forename: R A
authors.initials: RA
authors.lastname: Beinart
authors.forename: S V
authors.initials: SV
authors.lastname: Nyholm
authors.forename: N
authors.initials: N
authors.lastname: Dubilier
authors.forename: P R
authors.initials: PR
authors.lastname: Girguis
mesh_terms: D000818:Animals; D044822:Biodiversity; D060026:Endophytes / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D020563:Gammaproteobacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D005880:Gills / Q000382:microbiology / Q000502:physiology; D008969:Molecular Sequence Data; D010802:Phylogeny; D012908:Snails / Q000382:microbiology* / Q000502:physiology; D013559:Symbiosis