title: Presence, distribution, and diversity of iron-oxidizing bacteria at a landfill leachate-impacted groundwater surface water interface.
abstract: We examined the presence of iron-oxidizing bacteria (IOB) at a groundwater surface water interface (GSI) impacted by reduced groundwater originating as leachate from an upgradient landfill. IOB enrichments and quantifications were obtained, at high vertical resolution, by an iron/oxygen opposing gradient cultivation method. The depth-resolved soil distribution profiles of water content, Fe(2+), and total Fe indicated sharp gradients within the top 10 cm sediments of the GSI, where the IOB density was the highest. In addition, the vertical distribution of iron-reducing bacteria at the same sampling site mirrored the IOB distribution. Clone libraries from two separate IOB enrichments indicated a stratified IOB community with clear differences at short vertical distances. Alpha- and Betaproteobacteria were the dominant phylotypes. Clones from the near-surface sediment (1-2 cm below ground surface) were dominated by members of the Bradyrhizobiaceae and Comamonadaceae; clones from the deeper sediments were phylogenetically more diverse, dominated by members of the Rhodocyclaceae. The iron deposition profiles indicated that active iron oxidation occurred only within the near-to-surface GSI sediments. The match between the iron deposition profiles and the IOB abundance profiles strongly hints at the contribution of the IOB community to Fe oxidation in this Fe-rich GSI ecosystem.
authors.affiliation: Department of Civil and Environmental Engineering, University of Connecticut, Storrs, CT, USA.
authors.forename: Ran
authors.initials: R
authors.lastname: Yu
authors.forename: Ping
authors.initials: P
authors.lastname: Gan
authors.forename: Allison A
authors.initials: AA
authors.lastname: Mackay
authors.forename: Shouliang
authors.initials: S
authors.lastname: Zhang
authors.forename: Barth F
authors.initials: BF
authors.lastname: Smets
mesh_terms: D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification*; D001673:Biodegradation, Environmental; D004269:DNA, Bacterial / Q000235:genetics; D005296:Ferrous Compounds / Q000378:metabolism*; D005618:Fresh Water / Q000382:microbiology*; D015723:Gene Library; D019015:Geologic Sediments / Q000382:microbiology; D010084:Oxidation-Reduction; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012037:Refuse Disposal; D012987:Soil; D014871:Water Microbiology; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D004269:DNA, Bacterial; D005296:Ferrous Compounds; D012336:RNA, Ribosomal, 16S; D012987:Soil; D014874:Water Pollutants, Chemical