title: Population structure of microbial communities associated with two deep, anaerobic, alkaline aquifers.
abstract: Microbial communities of two deep (1,270 and 316 m) alkaline (pH 9.94 and 8.05), anaerobic (Eh, -137 and -27 mV) aquifers were characterized by rRNA-based analyses. Both aquifers, the Grande Ronde (GR) and Priest rapids (PR) formations, are located within the Columbia River Basalt Group in south-central Washington, and sulfidogenesis and methanogenesis characterize the GR and PR formations, respectively. RNA was extracted from microorganisms collected from groundwater by ultrafiltration through hollow-fiber membranes and hybridized to taxon-specific oligonucleotide probes. Of the three domains, Bacteria dominated both communities, making up to 92.0 and 64.4% of the total rRNA from the GR and PR formations, respectively. Eucarya comprised 5.7 and 14.4%, and Archaea comprised 1.8% and 2.5%, respectively. The gram-positive target group was found in both aquifers, 11.7% in GR and 7.6% in PR. Two probes were used to target sulfate- and/or metal-reducing bacteria within the delta subclass of Proteobacteria. The Desulfobacter groups was present (0.3%) only in the high-sulfate groundwater (GR). However, comparable hybridization to a probe selective for the desulfovibrios and some metal-reducing bacteria was found in both aquifers, 2.5 and 2.9% from the GR and PR formations, respectively. Selective PCR amplification and sequencing of the desulfovibrio/metal-reducing group revealed a predominance of desulfovibrios in both systems (17 of 20 clones), suggesting that their environmental distribution is not restricted by sulfate availability.
authors.affiliation: Department of Civil Engineering, Northwestern University, Evanston, Illinois 60208, USA.
authors.forename: N K
authors.initials: NK
authors.lastname: Fry
authors.forename: J K
authors.initials: JK
authors.lastname: Fredrickson
authors.forename: S
authors.initials: S
authors.lastname: Fishbain
authors.forename: M
authors.initials: M
authors.lastname: Wagner
authors.forename: D A
authors.initials: DA
authors.lastname: Stahl
mesh_terms: D000693:Anaerobiosis; D003901:Desulfovibrio / Q000145:classification* / Q000235:genetics; D004783:Environmental Microbiology; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction