PHYLOGENETIC DIVERSITY OF ARCHAEA AND BACTERIA IN A DEEP SUBSURFACE PALEOSOL

A low-biomass paleosol 188 m below the ground surface at the Departmen t of Energy's Hanford Site in south-central Washington State was recov ered and maintained at the in situ temperature (17 degrees C) as an in tact core or homogenized sediment for 0, 1, 3, 10, and 21 weeks post-s ampling. Bacterial and archaeal 16S rRNA genes were amplified by PCR a nd cloned. Of 746 bacterial and 190 archaeal clones that were categori zed by restriction fragment length polymorphism (RFLP), 242 bacterial and 16 archaeal clones were partially sequenced and compared against t he small subunit ribosomal RNA database (RDP) and GenBank. Six bacteri al and 16 archaeal clones sequences, with little similarity to those i n public databases, were sequenced in their entirety, and subjected to more detained phylogenetic analysis. The most frequently occurring cl ones types were related to Pseudomonas, Bacillus, Micrococcus, Claviba cter, Nocardioides, Burkholderia, Comamonas, and Erythromicrobium. Clo ne sequences whose RDP similarity value was greater than or equal to 0 .6 consistently grouped with their nearest RDP neighbor during phyloge netic analysis. Six truly novel eubacterial sequences were identified; they consistently cluster with or near the Chloroflexaceae and sequen ces recovered from the Sargasso Sea. Sixteen unique archaeal RFLP grou ps were identified from 190 randomly-sampled clones. The novel archaea l rDNA clones formed a coherent clade along the major Crenarchaea bran ch containing all previously described mesophilic crenarchae clones, b ut remained firmly associated with 16S rDNA clones previously obtained from a thermal Fe/S spring in Yellowstone National Park. The wealth o f group-specific genetic information identified during this study will now allow us to address specific hypotheses related to in situ stimul ation of these deep subsurface microorganisms and changes in microbial community composition resulting from subsurface contamination or reme diation processes at the Hanford Site.