MOLECULAR-IDENTIFICATION AND LOCALIZATION OF FILAMENTOUS SYMBIOTIC BACTERIA ASSOCIATED WITH THE HYDROTHERMAL VENT ANNELID ALVINELLA-POMPEJANA

Alvinella pompejana is a polychaetous annelid that inhabits high tempe rature environments associated with active deep-sea hydrothermal vents along the East Pacific Rise. A unique and diverse epibiotic microflor a with a prominent filamentous morphotype is found associated with the worm's dorsal integument. A previous study established the taxonomic positions of two epsilon proteobacterial phylotypes, 13B and 5A, which dominated a clone library of 16S rRNA genes amplified by PCR from the epibiotic microbial community of an A. pompejana specimen. In the pre sent study deoxyoligonucleotide PCR primers specific for phylotypes 13 B and 5A were used to demonstrate that these phylotypes are regular fe atures of the bacterial community associated with A. pompejana. Assayi ng of other surfaces around colonies of A. pompejana revealed that phy lotypes 13B and 5A are not restricted to A. pompejana. Phylotype 13B o ccurs on the exterior surfaces of other invertebrate genera and rock s urfaces, and phylotype 5A occurs on a congener, Alvinella caudata. The 13B and 5A phylotypes were identified and localized on A. pompejana b y in situ hybridization, demonstrating that these two phylotypes are, in fact, the prominent filamentous bacteria on the dorsal integument o f A. pompejana. These findings indicate that the filamentous bacterial symbionts of A. pompejana are epsilon Proteobacteria which do not hav e an obligate requirement for A. pompejana.