title: Hexavalent chromium reduction under fermentative conditions with lactate stimulated native microbial communities.
abstract: Microbial reduction of toxic hexavalent chromium (Cr(VI)) in-situ is a plausible bioremediation strategy in electron-acceptor limited environments. However, higher [Cr(VI)] may impose stress on syntrophic communities and impact community structure and function. The study objectives were to understand the impacts of Cr(VI) concentrations on community structure and on the Cr(VI)-reduction potential of groundwater communities at Hanford, WA. Steady state continuous flow bioreactors were used to grow native communities enriched with lactate (30 mM) and continuously amended with Cr(VI) at 0.0 (No-Cr), 0.1 (Low-Cr) and 3.0 (High-Cr) mg/L. Microbial growth, metabolites, Cr(VI), 16S rRNA gene sequences and GeoChip based functional gene composition were monitored for 15 weeks. Temporal trends and differences in growth, metabolite profiles, and community composition were observed, largely between Low-Cr and High-Cr bioreactors. In both High-Cr and Low-Cr bioreactors, Cr(VI) levels were below detection from week 1 until week 15. With lactate enrichment, native bacterial diversity substantially decreased as Pelosinus spp., and Sporotalea spp., became the dominant groups, but did not significantly differ between Cr concentrations. The Archaea diversity also substantially decreased after lactate enrichment from Methanosaeta (35%), Methanosarcina (17%) and others, to mostly Methanosarcina spp. (95%). Methane production was lower in High-Cr reactors suggesting some inhibition of methanogens. Several key functional genes were distinct in Low-Cr bioreactors compared to High-Cr. Among the Cr resistant microbes, Burkholderia vietnamiensis, Comamonas testosterone and Ralstonia pickettii proliferated in Cr amended bioreactors. In-situ fermentative conditions facilitated Cr(VI) reduction, and as a result 3.0 mg/L Cr(VI) did not impact the overall bacterial community structure.
authors.affiliation: ENIGMA - Ecosystems and Networks Integrated with Genes and Molecular Assemblies Program, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America ; Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America.
authors.forename: Anil C
authors.initials: AC
authors.lastname: Somenahally
authors.affiliation: ENIGMA - Ecosystems and Networks Integrated with Genes and Molecular Assemblies Program, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America ; Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America.
authors.forename: Jennifer J
authors.initials: JJ
authors.lastname: Mosher
authors.affiliation: Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America ; Institute for Environmental Genomics, Department of Botany, University of Oklahoma, Norman, Oklahoma, United States of America.
authors.forename: Tong
authors.initials: T
authors.lastname: Yuan
authors.affiliation: ENIGMA - Ecosystems and Networks Integrated with Genes and Molecular Assemblies Program, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America.
authors.forename: Mircea
authors.initials: M
authors.lastname: Podar
authors.affiliation: ENIGMA - Ecosystems and Networks Integrated with Genes and Molecular Assemblies Program, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America ; Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America ; Joint Biological Sciences Institute, University of Tennessee, Knoxville, Tennessee, United States of America.
authors.forename: Tommy J
authors.initials: TJ
authors.lastname: Phelps
authors.affiliation: ENIGMA - Ecosystems and Networks Integrated with Genes and Molecular Assemblies Program, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America ; Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America ; Joint Biological Sciences Institute, University of Tennessee, Knoxville, Tennessee, United States of America.
authors.forename: Steven D
authors.initials: SD
authors.lastname: Brown
authors.affiliation: ENIGMA - Ecosystems and Networks Integrated with Genes and Molecular Assemblies Program, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America ; Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America.
authors.forename: Zamin K
authors.initials: ZK
authors.lastname: Yang
authors.affiliation: ENIGMA - Ecosystems and Networks Integrated with Genes and Molecular Assemblies Program, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America ; Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America ; Department of Civil & Environmental Engineering, University of Tennessee, Knoxville, Tennessee, United States of America ; Department of Earth & Planetary Sciences, University of Tennessee, Knoxville, Tennessee, United States of America ; Department of Microbiology, University of Tennessee, Knoxville, Tennessee, United States of America ; Joint Biological Sciences Institute, University of Tennessee, Knoxville, Tennessee, United States of America.
authors.forename: Terry C
authors.initials: TC
authors.lastname: Hazen
authors.affiliation: ENIGMA - Ecosystems and Networks Integrated with Genes and Molecular Assemblies Program, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America ; Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America.
authors.forename: Adam P
authors.initials: AP
authors.lastname: Arkin
authors.affiliation: ENIGMA - Ecosystems and Networks Integrated with Genes and Molecular Assemblies Program, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America ; Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America ; Joint Biological Sciences Institute, University of Tennessee, Knoxville, Tennessee, United States of America.
authors.forename: Anthony V
authors.initials: AV
authors.lastname: Palumbo
authors.affiliation: ENIGMA - Ecosystems and Networks Integrated with Genes and Molecular Assemblies Program, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America ; Institute for Environmental Genomics, Department of Botany, University of Oklahoma, Norman, Oklahoma, United States of America.
authors.forename: Joy D
authors.initials: JD
authors.lastname: Van Nostrand
authors.affiliation: ENIGMA - Ecosystems and Networks Integrated with Genes and Molecular Assemblies Program, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America ; Institute for Environmental Genomics, Department of Botany, University of Oklahoma, Norman, Oklahoma, United States of America.
authors.forename: Jizhong
authors.initials: J
authors.lastname: Zhou
authors.affiliation: ENIGMA - Ecosystems and Networks Integrated with Genes and Molecular Assemblies Program, Lawrence Berkeley National Laboratory, Berkeley, California, United States of America ; Biosciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States of America ; Joint Biological Sciences Institute, University of Tennessee, Knoxville, Tennessee, United States of America.
authors.forename: Dwayne A
authors.initials: DA
authors.lastname: Elias
mesh_terms: D001105:Archaea / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D001419:Bacteria / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D001673:Biodegradation, Environmental / Q000187:drug effects; D019149:Bioreactors / Q000382:microbiology; D002857:Chromium / Q000378:metabolism* / Q000633:toxicity; D004305:Dose-Response Relationship, Drug; D005285:Fermentation / Q000187:drug effects*; D060587:Groundwater / Q000737:chemistry / Q000382:microbiology; D019344:Lactic Acid / Q000494:pharmacology*; D010084:Oxidation-Reduction / Q000187:drug effects; D014874:Water Pollutants, Chemical / Q000378:metabolism* / Q000633:toxicity
chemical_list: D014874:Water Pollutants, Chemical; D002857:Chromium; C074702:chromium hexavalent ion; D019344:Lactic Acid