Characterization of bacterial processes in the subsurface and the atmosphere:

This dissertation describes research that seeks to expand understanding of bacterially-mediated biotransformation in subsurface groundwater and the atmosphere. In the first study a highly tetrachloroethene (PCE)-enriched culture, RU11/PCE was developed from contaminated aquifer materials. Denaturing gradient gel electrophoresis (DGGE), 16S rRNA clonal library analysis, and direct sequencing of 16S rRNA, sod and gyrB genes revealed a single bacterial species, Dehalococcoides, in the RU11/PCE culture. However, because the 16S rRNA, sod and gyrB genes of the Dehalococcoides spp. are highly conserved, the possibility that more than one strain of Dehalococcoides was present could not be conclusively eliminated. The reductive dehalogenase gene profile of the RU11/PCE culture was different than that of other previously reported Dehalococcoides pure cultures and unlike other chloroethene-respiring Dehalococcoides spp., RU11/PCE grew on PCE, TCE, cis-1,2-DCE or VC. The second study addressed the hypothesis that the air contains an active microbial ecosystem. Rotating bioaerosol bioreactors were manufactured to keep bacteria suspended in the presence of a volatile substrate while measuring their activity. A qPCR method was developed and used along with an ATP assay, microscopy, and plate counts to enumerate airborne bacteria. Although the gas-phase reactors could retain bacteria and volatile substrates for days, results using live aerosolized Xanthobacter autotrophicus and Bacillus subtilis indicated no growth. In tests with X. autotrophicus, no culturable cells were recovered under any condition. B. subtilis aerosols from dilute substrate yielded higher culturability than aerosols from distilled water with no TSB substrate. Lack of culturability occurred despite presence of airborne bacteria over time, as measured by qPCR and ATP. Techniques were also developed to characterize microbial communities in atmospheric samples. The bacterial components of a pooled sample of atmospheric water collected in the vicinity of Oklahoma City, OK were analyzed using DGGE and clone library analysis. From DGGE analysis, six out of eight strains detected belong to the phyla of Actinobacteria, Firmicutes, Proteobacteria and Bacteriodetes. In clone library analysis, 12 bacterial strains were identified (from 78 total) with dominant occurrence of the genera, Sphingomonas, Pedobacter, and Curtobacterium spp. The bacterial populations detected from the two methods were composed of strains of diverse origins.Ph.D.Includes bibliographical references (p. 162-179)by Eun Kyeu So