title: Bacterial symbionts of Bathymodiolus mussels and Escarpia tubeworms from Chapopote, an asphalt seep in the Southern Gulf of Mexico.
abstract: Chemosynthetic life was recently discovered at Chapopote, an asphalt hydrocarbon seep in the southern Gulf of Mexico. Preliminary morphological analyses indicated that one tubeworm and two mussel species colonize Chapopote. Our molecular analyses identified the tubeworm as Escarpia sp., and the mussels as Bathymodiolus heckerae and B. brooksi. Comparative 16S rRNA analysis and FISH showed that all three species harbour intracellular sulfur-oxidizing symbionts highly similar or identical to those found in the same host species from northern Gulf of Mexico (nGoM). The mussels also harbour methane-oxidizing symbionts, and these shared highly similar to identical 16S rRNA sequences to their nGoM conspecifics. We discovered a novel symbiont in B. heckerae, which is closely related to hydrocarbon-degrading bacteria of the genus Cycloclasticus. In B. heckerae, we found key genes for the use of aromatic compounds, and its stable carbon isotope values were consistently higher than B. brooksi, indicating that the novel symbiont might use isotopically heavy aromatic hydrocarbons from the asphalt seep. This discovery is particularly intriguing because until now only methane and reduced sulfur compounds have been shown to power cold-seep chemosynthetic symbioses. The abundant hydrocarbons available at Chapopote would provide these mussel symbioses with a rich source of nutrition.
authors.affiliation: Max Planck Institute for Marine Microbiology, Celsiusstr. 1, 28359 Bremen, Germany.
authors.forename: L
authors.initials: L
authors.lastname: Raggi
authors.forename: F
authors.initials: F
authors.lastname: Schubotz
authors.forename: K-U
authors.initials: KU
authors.lastname: Hinrichs
authors.forename: N
authors.initials: N
authors.lastname: Dubilier
authors.forename: J M
authors.initials: JM
authors.lastname: Petersen
mesh_terms: D000446:Aldehyde-Lyases / Q000032:analysis; D000818:Animals; D001419:Bacteria / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D018407:Bacterial Physiological Phenomena; D044822:Biodiversity; D049872:Bivalvia / Q000145:classification / Q000235:genetics / Q000382:microbiology*; D002247:Carbon Isotopes / Q000032:analysis; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis; D003576:Electron Transport Complex IV / Q000235:genetics; D060851:Gulf of America; D008969:Molecular Sequence Data; D010802:Phylogeny; D011077:Polychaeta / Q000145:classification / Q000235:genetics / Q000382:microbiology*; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013559:Symbiosis
chemical_list: D002247:Carbon Isotopes; D012336:RNA, Ribosomal, 16S; D003577:Cytochrome P-450 Enzyme System; D003576:Electron Transport Complex IV; D000446:Aldehyde-Lyases; C054540:hydroperoxide lyase