Mustoe George E
Geology Department, Western Washington University, Bellingham, WA 98225, USA.
Microorganisms. 2018 Jan 15;6(1):8. doi: 10.3390/microorganisms6010008.
A sandstone outcrop exposed to freshwater seepage supports a diverse assemblage of photosynthetic microbes. Dominant taxa are two cyanophytes ( sp., sp.) and a unicellular green alga ( sp.). Less abundant taxa include a filamentous green alga, , and the desmid . 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, 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.
一处暴露于淡水渗流的砂岩露头支撑着多种光合微生物群落。主要类群有两种蓝藻（属，属）和一种单细胞绿藻（属）。数量较少的类群包括一种丝状绿藻和鼓藻。通过测量叶绿素和脂质水平证明了生物活性。生物测定方法证实了这些微生物溶解和代谢来自含铁矿物中铁的能力。色谱分析表明柠檬酸可能是螯合剂；这种低分子量有机酸在砂岩的间隙流体中可检测到，测量值为0.0756毫克/毫升。使用模式生物菌株UTEX 650进行的生物测定表明，不同含铁矿物中铁的有效性各不相同。按铁有效性从高到低的顺序排列为：磁铁矿>褐铁矿>黑云母>菱铁矿>赤铁矿。选择黑云母进行详细研究，因为它是砂岩中最丰富的含铁矿物。扫描电子显微镜图像支持了微生物学证据，显示与其他硅酸盐矿物相对未受损的颗粒相比，黑云母发生了风化。
