title: Independent phylogenetic origins of methanotrophic and chemoautotrophic bacterial endosymbioses in marine bivalves.
abstract: The discovery of bacterium-bivalve symbioses capable of utilizing methane as a carbon and energy source indicates that the endosymbionts of hydrothermal vent and cold seep bivalves are not restricted to sulfur-oxidizing chemoautotrophic bacteria but also include methanotrophic bacteria. The phylogenetic origin of methanotrophic endosymbionts and their relationship to known symbiotic and free-living bacteria, however, have remained unexplored. In situ localization and phylogenetic analysis of a symbiont 16S rRNA gene cloned from the gills of a recently described deep-sea mussel species demonstrate that this symbiont represents a new taxon which is closely related to free-living, cultivable Type I methanotrophic bacteria. This symbiont is distinct from known chemoautotrophic symbionts. Thus, despite compelling similarities between the symbioses, chemoautotrophic and methanotrophic symbionts of marine bivalves have independent phylogenetic origins.
authors.affiliation: Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138.
authors.forename: D L
authors.initials: DL
authors.lastname: Distel
authors.forename: C M
authors.initials: CM
authors.lastname: Cavanaugh
mesh_terms: D000818:Animals; D001419:Bacteria / Q000145:classification* / Q000235:genetics; D001483:Base Sequence; D005075:Biological Evolution; D049872:Bivalvia / Q000382:microbiology* / Q000648:ultrastructure; D004275:DNA, Ribosomal / Q000235:genetics; D005880:Gills / Q000382:microbiology / Q000648:ultrastructure; D017403:In Situ Hybridization; D008772:Methylococcaceae / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification / Q000648:ultrastructure; D008969:Molecular Sequence Data; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013559:Symbiosis
chemical_list: D004275:DNA, Ribosomal; D012336:RNA, Ribosomal, 16S