title: The impact of gamma radiation on sediment microbial processes.
abstract: Microbial communities have the potential to control the biogeochemical fate of some radionuclides in contaminated land scenarios or in the vicinity of a geological repository for radioactive waste. However, there have been few studies of ionizing radiation effects on microbial communities in sediment systems. Here, acetate and lactate amended sediment microcosms irradiated with gamma radiation at 0.5 or 30 Gy h(-1) for 8 weeks all displayed NO3 (-) and Fe(III) reduction, although the rate of Fe(III) reduction was decreased in 30-Gy h(-1) treatments. These systems were dominated by fermentation processes. Pyrosequencing indicated that the 30-Gy h(-1) treatment resulted in a community dominated by two Clostridial species. In systems containing no added electron donor, irradiation at either dose rate did not restrict NO3 (-), Fe(III), or SO4 (2-) reduction. Rather, Fe(III) reduction was stimulated in the 0.5-Gy h(-1)-treated systems. In irradiated systems, there was a relative increase in the proportion of bacteria capable of Fe(III) reduction, with Geothrix fermentans and Geobacter sp. identified in the 0.5-Gy h(-1) and 30-Gy h(-1) treatments, respectively. These results indicate that biogeochemical processes will likely not be restricted by dose rates in such environments, and electron accepting processes may even be stimulated by radiation.
authors.affiliation: Williamson Research Centre for Molecular Environmental Science and Research Centre for Radwaste and Decommissioning, School of Earth, Atmospheric, and Environmental Sciences, University of Manchester, Manchester, United Kingdom.
authors.forename: Ashley R
authors.initials: AR
authors.lastname: Brown
authors.affiliation: Williamson Research Centre for Molecular Environmental Science and Research Centre for Radwaste and Decommissioning, School of Earth, Atmospheric, and Environmental Sciences, University of Manchester, Manchester, United Kingdom.
authors.forename: Christopher
authors.initials: C
authors.lastname: Boothman
authors.affiliation: Dalton Cumbrian Facility, Westlakes Science and Technology Park, Cumbria, United Kingdom School of Chemistry, University of Manchester, Manchester, United Kingdom.
authors.forename: Simon M
authors.initials: SM
authors.lastname: Pimblott
authors.affiliation: Williamson Research Centre for Molecular Environmental Science and Research Centre for Radwaste and Decommissioning, School of Earth, Atmospheric, and Environmental Sciences, University of Manchester, Manchester, United Kingdom jon.lloyd@manchester.ac.uk.
authors.forename: Jonathan R
authors.initials: JR
authors.lastname: Lloyd
mesh_terms: D000085:Acetates / Q000378:metabolism; D000068016:Eubacteriales / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology / Q000528:radiation effects; D005285:Fermentation / Q000528:radiation effects; D005290:Ferric Compounds / Q000378:metabolism; D005720:Gamma Rays; D045302:Geobacter / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology / Q000528:radiation effects; D019015:Geologic Sediments / Q000382:microbiology*; D059014:High-Throughput Nucleotide Sequencing; D007773:Lactates / Q000378:metabolism; D059013:Microbial Consortia / Q000502:physiology* / Q000528:radiation effects*; D010084:Oxidation-Reduction; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S; D011850:Radioactive Waste
chemical_list: D000085:Acetates; D005290:Ferric Compounds; D007773:Lactates; D012336:RNA, Ribosomal, 16S; D011850:Radioactive Waste
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