Bacteria associated with iron seeps in a sulfur-rich, neutral pH, freshwater ecosystem

Abstract

The freshwater nature reserve De Bruuk is an iron-and sulfur-rich minerotrophic peatland containing many iron seeps and forms a suitable habitat for iron and sulfur cycle bacteria. Analysis of 16S rRNA gene-based clone libraries showed a striking correlation of the bacterial population of samples from this freshwater ecosystem with the processes of iron reduction (genus Geobacter), iron oxidation (genera Leptothrix and Gallionella) and sulfur oxidation (genus Sulfuricurvum).Results from fluorescence in situ hybridization analyses with a probe specific for the beta-1 subgroup of Proteobacteria, to which the genera Leptothrix and Gallionella belong, and newly developed probes specific for the genera Geobacter and Sulfuricurvum, supported the clone library data. Molecular data suggested members of the epsilonproteobacterial genus Sulfuricurvum as contributors to the oxidation of reduced sulfur compounds in the iron seeps of De Bruuk. In an evaluation of anaerobic dimethyl sulfide (DMS)-degrading activity of sediment, incubations with the electron acceptors sulfate, ferric iron and nitrate were performed. The fastest conversion of DMS was observed with nitrate. Further, a DMS-oxidizing, nitrate-reducing enrichment culture was established with sediment material from De Bruuk. This culture was dominated by dimorphic, prosthecate bacteria, and the 16S rRNA gene sequence obtained from this enrichment was closely affiliated with Hyphomicrobium facile, which indicates that the Hyphomicrobium species are capable of both aerobic and nitrate-driven DMS degradation.

Diversity of the Sediment Microbial Community in the Aha Watershed (Southwest China) in Response to Acid Mine Drainage Pollution Gradients

“…It is possible that other environmental factors may have affected the abundance of Acidithiobacillus and Thiobacillus. Gallionella is an FeOB commonly detected in neutral environments (46)(47)(48); however, it exhibited very low abundance in neutral downstream samples from this study. Other FeOB, including Aciditerrimonas, Thermomonas, and Aquabacterium, were also detected at lower abundances in the current study.…”

Repeated Anaerobic Microbial Redox Cycling of Iron

“…These results are analogous to those of a previous experiment with natural-sediment microflora in which Fe went through a single cycle of Fe reduction and oxidation (60) and to those of experiments with cocultures of Geobacter bremensis (53) or Geobacter sulfurreducens (7) (neither of which reduce nitrate) and the lithoautotrophic nitrate-reducing, Fe(II)-oxidizing enrichment culture of Straub et al (52). Together these studies suggest that microbial Fe cycling communities are likely to be present and active in anoxic soil and sedimentary environments experiencing shifts in organic carbon and nitrate input, analogous to those known to be present in aerobic/anaerobic interfacial environments (6,8,23,47). When inputs of organic carbon are high compared to nitrate, organic carbon oxidation by nitratereducing bacteria exhausts available nitrate, thus allowing microbial Fe(III) reduction to become the predominant TEAP (4,32,34,57).…”

Use of stable isotope probing to identify bacterial species involved in CO₂ fixation in the water just below the oxycline of the meromictic Lake Suigetsu, Japan

“…3D). Surveys using molecular detection techniques revealed widespread distribution of bacteria belonging to the class Epsilonproteobacteria in various sulfur-rich environments such as a cave sulfidic spring, a hydrothermal vent, a redox cline in the stratified ocean and an iron seep area (Engel et al 2004, Nakagawa et al 2005, Grote et al 2008, Haaijer et al 2008. Some bacteria belonging to the class Epsilonproteobacteria grow chemolithotrophically using sulfur compounds as energy sources and/or electron acceptors (Nakagawa and Takaki 2009).…”