Microbial Diversity in Actively Forming Iron Oxides from Weathered Banded Iron Formation Systems

• Published in: Microbes and Environments Vol. 33; no. 4; pp. 385 - 393
• Main Authors: Gagen, Emma J., Levett, Alan, Shuster, Jeremiah, Fortin, Danielle, Vasconcelos, Paulo M., Southam, Gordon
• Format: Journal Article
• Language: English; Japanese
• Published: Japan Japanese Society of Microbial Ecology / Japanese Society of Soil Microbiology / Taiwan Society of Microbial Ecology / Japanese Society of Plant Microbe Interactions / Japanese Society for Extremophiles 2018; Japan Science and Technology Agency; the Japanese Society of Microbial Ecology (JSME)/the Japanese Society of Soil Microbiology (JSSM)/the Taiwan Society of Microbial Ecology (TSME)/the Japanese Society of Plant Microbe Interactions (JSPMI)
• Subjects: Anaerobic conditions; Anaeromyxobacter; Aridity; Bacteria; Biogeochemical cycle; Biogeochemical cycles; Biogeochemistry; Biological activity; canga; Caves; Cementation; Chemical precipitation; Cyanobacteria; Dissolution; Dissolving; Ecosystems; Heterotrophic organisms; Heterotrophs; Identification; Iron; iron duricrust; Iron ores; Iron oxides; Iron-oxidizing bacteria; Iron-reducing bacteria; Karijini; Leptothrix; Microorganisms; Microscopy; Minerals; Mining; National parks; Niches; Oxidation; Oxide minerals; Oxides; Oxidizing agents; Precipitates; Restoration; Sheaths; Karijini; Leptothrix; canga; iron duricrust; Anaeromyxobacter
• ISSN: 1342-6311; 1347-4405
• DOI: 10.1264/jsme2.ME18019

The surface crust that caps highly weathered banded iron formations (BIFs) supports a unique ecosystem that is a post-mining restoration priority in iron ore areas. Geochemical evidence indicates that biological processes drive the dissolution of iron oxide minerals and contribute to the ongoing evolution of this duricrust. However, limited information is available on present-day biogeochemical processes in these systems, particularly those that contribute to the precipitation of iron oxides and, thus, the cementation and stabilization of duricrusts. Freshly formed iron precipitates in water bodies perched on cangas in Karijini National Park, Western Australia, were sampled for microscopic and molecular analyses to understand currently active microbial contributions to iron precipitation in these areas. Microscopy revealed sheaths and stalks associated with iron-oxidizing bacteria. The iron-oxidizing lineages Sphaerotilus, Sideroxydans, and Pedomicrobium were identified in various samples and Leptothrix was common in four out of five samples. The iron-reducing bacteria Anaeromyxobacter dehalogens and Geobacter lovleyi were identified in the same four samples, with various heterotrophs and diverse cyanobacteria. Given this arid, deeply weathered environment, the driver of contemporary iron cycling in Karijini National Park appears to be iron-reducing bacteria, which may exist in anaerobic niches through associations with aerobic heterotrophs. Overall oxidizing conditions and Leptothrix iron-oxidizers contribute to net iron oxide precipitation in our sampes, rather than a closed biogeochemical cycle, which would result in net iron oxide dissolution as has been suggested for canga caves in Brazil. Enhancements in microbial iron oxide dissolution and subsequent reprecipitation have potential as a surface-crust-ecosystem remediation strategy at mine sites.