title: Anoxic iron cycling bacteria from an iron sulfide- and nitrate-rich freshwater environment.
abstract: In this study, both culture-dependent and culture-independent methods were used to determine whether the iron sulfide mineral- and nitrate-rich freshwater nature reserve Het Zwart Water accommodates anoxic microbial iron cycling. Molecular analyses (16S rRNA gene clone library and fluorescence in situ hybridization, FISH) showed that sulfur-oxidizing denitrifiers dominated the microbial population. In addition, bacteria resembling the iron-oxidizing, nitrate-reducing Acidovorax strain BrG1 accounted for a major part of the microbial community in the groundwater of this ecosystem. Despite the apparent abundance of strain BrG1-like bacteria, iron-oxidizing nitrate reducers could not be isolated, likely due to the strictly autotrophic cultivation conditions adopted in our study. In contrast an iron-reducing Geobacter sp. was isolated from this environment while FISH and 16S rRNA gene clone library analyses did not reveal any Geobacter sp.-related sequences in the groundwater. Our findings indicate that iron-oxidizing nitrate reducers may be of importance to the redox cycling of iron in the groundwater of our study site and illustrate the necessity of employing both culture-dependent and independent methods in studies on microbial processes.
authors.affiliation: Department of Microbiology, Institute for Water and Wetland Research, Radboud University Nijmegen Nijmegen, Netherlands.
authors.forename: Suzanne C M
authors.initials: SC
authors.lastname: Haaijer
authors.forename: Gijs
authors.initials: G
authors.lastname: Crienen
authors.forename: Mike S M
authors.initials: MS
authors.lastname: Jetten
authors.forename: Huub J M
authors.initials: HJ
authors.lastname: Op den Camp