The symbioses between the vestimentiferan tubeworms and their chemosynthetic partners (Gammaproteobacteria, Chromatiales and Sedimenticolaceae) hallmark the success of these organisms in hydrothermal vent and hydrocarbon seep deep-sea habitats. The fidelity of these associations varies, as both the hosts and the symbionts can be loose in partner choice. Some tubeworms may host distinct symbiont phylotypes, which often co-occur in a single host individual. To better understand the genetic basis for the promiscuity of tubeworm symbioses, we assembled and investigated metagenome-assembled genomes of two symbiont phylotypes (species, based on the average nucleotide identity < 95%) in Lamellibrachia anaximandri, a vestimentiferan endemic to the Mediterranean Sea, in individuals collected from Palinuro hydrothermal vents (Italy) and hydrocarbon seeps (Eratosthenes seamount and Palmahim disturbance). Using comparative genomics, we show that mainly mobilome and genes involved in defence mechanisms distinguish the symbiont genotypes. While many central metabolic functions are conserved in the tubeworm symbionts, nitrate respiration (Nar, Nap and Nas proteins) is modular, yet this modularity is not linked to phylotype, but rather to geographic location, potentially implying adaptation to the local environment. Our results hint that variation in a single moonlighting protein may be responsible for the fidelity of these symbioses.
Bibliographical noteFunding Information:
This research used samples and data provided by the E/V Nautilus Exploration Program: expeditions NA008, NA009, NA015 and NA019. The authors would like to thank all individuals who helped during the expedition, including on‐board technical and scientific personnel, and the captain and crew of the E/V Nautilus. This study is funded by the Israeli Science Foundation (ISF) Grant 913/19 to MRB and the Morris Kahn Marine Research Station. The authors also thank the anonymous reviewers for their constructive comments.
© 2021 Society for Applied Microbiology and John Wiley & Sons Ltd.
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics
- Agricultural and Biological Sciences (miscellaneous)