Phylogenetic diversity of the bacterial community from a microbial mat at an active, hydrothermal vent system, Loihi Seamount, Hawaii

C. L. Moyer, F. C. Dobbs and D. M. Karl

Department of Oceanography, School of Ocean and Earth Science and Technology, University of Hawaii, Honolulu, Hawaii 96822

(Received 26 September 1994; Accepted 9 January 1995>

Abstract

The phylogenetic diversity of small-subunit rRNA genes associated with the domain Bacteria was examined (by using previously defined operational taxonomic units [C. L. Moyer, F. C. Dobbs, and D. M. Karl, Appl. Environ. Microbiol. 60:871 879, 1994]; those for Pele's Vents Bacteria are hereafter abbreviated PVB OTUs) with samples from a microbial mat at an active, deep-sea hydrothermal vent system. A cluster of phylogenetically related PVB OTUs (OTUs 2, 3, 6, and 8) was closely affiliated with Thiovulum sp. contained within the e subclass of the class Proteobacteria and accounted for 60.5% of the small-subunit rRNA bacterial clone library from Pele's Vents. A second, smaller cluster of PVB OTUs (OTUs 1 and 11) was closely affiliated with Xanthomonas sp., contained within the γ subclass of the Proteobacteria and accounted for a total of 27.1% of the bacterial clone library. The remaining five PVB OTUs each accounted for 2.1% of the clones recovered and were affiliated with the following phylogenetic groups; PVB OTU 12 was a member of the Colwellia assemblage; PVB OTU 4 was loosely determined to be a member of the Thiothrix group, with the endosymbiotic bacteria from Bathymodiolus thermophilus and Calyptogena magnifica as the nearest relatives; PVB OTU 10B was a member of the Myxobacterium group; and PVB OTU 9A was a member of the Paraphyletic assemblage, with the Octopus Spring microbial mat type K clone as the closest known relative. PVB OTU 7 was determined to be a PCR-generated chimeric structure combined from two described phylotypes detected in this study, thereby decreasing the previously estimated number of major PVB OTUs from 12 to 11.