TY - JOUR
T1 - Environmental Acquisition of Thiotrophic Endosymbionts by Deep-Sea Mussels of the Genus Bathymodiolus
AU - Won, Yong Jin
AU - Hallam, Steven J.
AU - O'Mullan, Gregory D.
AU - Pan, Irvin L.
AU - Buck, Kurt R.
AU - Vrijenhoek, Robert C.
PY - 2003/11
Y1 - 2003/11
N2 - Deep-sea Bathymodiolus mussels, depending on species and location, have the capacity to host sulfur-oxidizing (thiotrophic) and methanotrophic eubacteria in gill bacteriocytes, although little is known about the mussels' mode of symbiont aequisition. Previous studies of Bathymodiolus host and symbiont relationships have been based on collections of nonoverlapping species across wide-ranging geographic settings, creating an apparent model for vertical transmission. We present genetic and cytological evidence for the environmental acquisition of thiotrophic endosymbionts by vent mussels from the Mid-Atlantic Ridge. Open pit structures in cell membranes of the gill surface revealed likely sites for endocytosis of free-living bacteria. A population genetic analysis of the thiotrophic symbionts exploited a hybrid zone where two Bathymodiolus species intergrade. Northern Bathymodiolus azoricus and southern Bathymodiolus puteoserpentis possess species-specific DNA sequences that identify both their symbiont strains (internal transcribed spacer regions) and their mitochondria (ND4). However, the northern and southern symbiont-mitochondrial pairs were decoupled in the hybrid zone. Such decoupling of symbiont-mitochondrial pairs would not occur if the two elements were transmitted strictly vertically through the germ line. Taken together, these findings are consistent with an environmental source of thiotrophic symbionts in Bathymodiolus mussels, although an environmentally "leaky" system of vertical transmission could not be excluded.
AB - Deep-sea Bathymodiolus mussels, depending on species and location, have the capacity to host sulfur-oxidizing (thiotrophic) and methanotrophic eubacteria in gill bacteriocytes, although little is known about the mussels' mode of symbiont aequisition. Previous studies of Bathymodiolus host and symbiont relationships have been based on collections of nonoverlapping species across wide-ranging geographic settings, creating an apparent model for vertical transmission. We present genetic and cytological evidence for the environmental acquisition of thiotrophic endosymbionts by vent mussels from the Mid-Atlantic Ridge. Open pit structures in cell membranes of the gill surface revealed likely sites for endocytosis of free-living bacteria. A population genetic analysis of the thiotrophic symbionts exploited a hybrid zone where two Bathymodiolus species intergrade. Northern Bathymodiolus azoricus and southern Bathymodiolus puteoserpentis possess species-specific DNA sequences that identify both their symbiont strains (internal transcribed spacer regions) and their mitochondria (ND4). However, the northern and southern symbiont-mitochondrial pairs were decoupled in the hybrid zone. Such decoupling of symbiont-mitochondrial pairs would not occur if the two elements were transmitted strictly vertically through the germ line. Taken together, these findings are consistent with an environmental source of thiotrophic symbionts in Bathymodiolus mussels, although an environmentally "leaky" system of vertical transmission could not be excluded.
UR - http://www.scopus.com/inward/record.url?scp=0242573192&partnerID=8YFLogxK
U2 - 10.1128/AEM.69.11.6785-6792.2003
DO - 10.1128/AEM.69.11.6785-6792.2003
M3 - Article
C2 - 14602641
AN - SCOPUS:0242573192
SN - 0099-2240
VL - 69
SP - 6785
EP - 6792
JO - Applied and Environmental Microbiology
JF - Applied and Environmental Microbiology
IS - 11
ER -