title: Identification and isolation of a Castellaniella species important during biostimulation of an acidic nitrate- and uranium-contaminated aquifer.
abstract: Immobilization of uranium in groundwater can be achieved through microbial reduction of U(VI) to U(IV) upon electron donor addition. Microbial community structure was analyzed in ethanol-biostimulated and control sediments from a high-nitrate (>130 mM), low-pH, uranium-contaminated site in Oak Ridge, TN. Analysis of small subunit (SSU) rRNA gene clone libraries and polar lipid fatty acids from sediments revealed that biostimulation resulted in a general decrease in bacterial diversity. Specifically, biostimulation resulted in an increase in the proportion of Betaproteobacteria (10% of total clones in the control sediment versus 50 and 79% in biostimulated sediments) and a decrease in the proportion of Gammaproteobacteria and Acidobacteria. Clone libraries derived from dissimilatory nitrite reductase genes (nirK and nirS) were also dominated by clones related to Betaproteobacteria (98% and 85% of total nirK and nirS clones, respectively). Within the nirK libraries, one clone sequence made up 59 and 76% of sequences from biostimulated sediments but only made up 10% of the control nirK library. Phylogenetic analysis of SSU rRNA and nirK gene sequences from denitrifying pure cultures isolated from the site indicate that all belong to a Castellaniella species; nearly identical sequences also constituted the majority of biostimulated SSU rRNA and nirK clone libraries. Thus, by combining culture-independent with culture-dependent techniques, we were able to link SSU rRNA clone library information with nirK sequence data and conclude that a potentially novel Castellaniella species is important for in situ nitrate removal at this site.
authors.affiliation: University of Oklahoma, Department of Botany and Microbiology, Norman, OK 73019, USA.
authors.forename: Anne M
authors.initials: AM
authors.lastname: Spain
authors.forename: Aaron D
authors.initials: AD
authors.lastname: Peacock
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Istok
authors.forename: Mostafa S
authors.initials: MS
authors.lastname: Elshahed
authors.forename: Fares Z
authors.initials: FZ
authors.lastname: Najar
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Roe
authors.forename: David C
authors.initials: DC
authors.lastname: White
authors.forename: Lee R
authors.initials: LR
authors.lastname: Krumholz
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D020562:Betaproteobacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D003470:Culture Media; D000431:Ethanol / Q000378:metabolism; D005618:Fresh Water / Q000737:chemistry / Q000382:microbiology*; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D009566:Nitrates / Q000032:analysis / Q000378:metabolism; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D014501:Uranium / Q000032:analysis; D014876:Water Pollution; D014881:Water Supply
chemical_list: D001426:Bacterial Proteins; D003470:Culture Media; D009566:Nitrates; D000431:Ethanol; D014501:Uranium