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Acknowledgement to Reviewers of Microorganisms in 2017
Open AccessArticle

Biogenic Weathering: Solubilization of Iron from Minerals by Epilithic Freshwater Algae and Cyanobacteria

Geology Department, Western Washington University, Bellingham, WA 98225, USA
Microorganisms 2018, 6(1), 8; https://doi.org/10.3390/microorganisms6010008
Received: 8 December 2017 / Revised: 29 December 2017 / Accepted: 9 January 2018 / Published: 15 January 2018
A sandstone outcrop exposed to freshwater seepage supports a diverse assemblage of photosynthetic microbes. Dominant taxa are two cyanophytes (Oscillatoria sp., Rivularia sp.) and a unicellular green alga (Palmellococcus sp.). Less abundant taxa include a filamentous green alga, Microspora, and the desmid Cosmarium. Biologic activity is evidenced by measured levels of chlorophyll and lipids. Bioassay methods confirm the ability of these microbes to dissolve and metabolize Fe from ferruginous minerals. Chromatographic analysis reveals citric acid as the likely chelating agent; this low molecular weight organic acid is detectable in interstitial fluid in the sandstone, measured as 0.0756 mg/mL. Bioassays using a model organism, Synechoccus elongates strain UTEX 650, show that Fe availability varies among different ferruginous minerals. In decreasing order of Fe availability: magnetite > limonite > biotite > siderite > hematite. Biotite was selected for detailed study because it is the most abundant iron-bearing mineral in the sandstone. SEM images support the microbiologic evidence, showing weathering of biotite compared to relatively undamaged grains of other silicate minerals. View Full-Text
Keywords: algae; bioassay; biogenic weathering; biotite; chelation; cyanophyte; epilithic; iron minerals algae; bioassay; biogenic weathering; biotite; chelation; cyanophyte; epilithic; iron minerals
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Mustoe, G.E. Biogenic Weathering: Solubilization of Iron from Minerals by Epilithic Freshwater Algae and Cyanobacteria. Microorganisms 2018, 6, 8.

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