Microbial participation in the formation of siliceous scale from geothermal waters and scale control

1.硅质结垢形成实验：在日本九州大分县的大竹地热发电厂进行了硅质矿床的研究。1994年6月至12月和1995年9月至12月分别将薄铜板浸入老化池的地热水中。测定了地热水的温度、pH和SiO2含量。硅质沉积物在平板上呈圆柱状生长。将板上的硅质沉积物从地热水中轻轻取出，立即放入液氮中，并在-20ºC下保存直至使用。矿物学研究：在显微镜下和x射线衍射分析下检查了硅质矿床。用x射线荧光测定化学成分。水垢由无机矿物相组成，形成于原位、井口和深部。微生物参与的调查：在铜板上形成的无定形二氧化硅中观察到许多棒状细菌细胞，在pH 7.2和85(]SY.+- . [)2 - C的条件下，在地热热水中发现更多。(1)溶菌酶和冻融法可稳定提取硅质沉积物中的大量基因组DNA。随着孵育时间的延长，单个铜板上形成的硅质沉积物体积和从硅质沉积物中提取的基因组DNA数量呈指数增长。(2)通过对PCR获得的部分16S rRNA基因进行克隆和测序，研究了这些DNA提取物的系统发育多样性。细菌群落主要由细菌域的三种系统发育类型组成。第1簇（8个无性系）与水仙属亲缘关系密切，第2簇（15个无性系）与水仙属亲缘关系密切。第三簇（2个克隆）与革兰氏阳性厌氧嗜热细菌序列同源。这些极度嗜热的细菌可能有助于无定形二氧化硅的快速聚集，并可能作为确定生物矿化过程中硅质矿床形成速率的参数。少

1.Experiments of siliceous scale formation : Studies on siliceous deposits were carried out at the Otake geothermal power plant, Oita prefecture, Kyushu, Japan. Thin copper plates were immersed in the geothermal water of the aging tank, from June to December, 1994 and from September to December, 1995. Temperatures, pH and SiO2 content of the geothermal water were measured. The siliceous deposits grew cylindrically on the plate. The siliceous deposit on the plate was gently removed from the geothermal water and placed immediately in liquid nitrogen and stored at -20ﾟC until use.2.Mineralogical studies : The siliceous deposits were examined under the microscope and by X-ray diffraction analysis. The chemical composition was determined by X-ray fluorescence. Scale consists of namy mineral phases, which formed in situ, in the well head and in depth.3.Investigation of microbial participation : Numerousrod-shaped bacterial cells were observed in amorphous silica formed on the copper plate pl … More aced in geothermal hot water, under conditions of pH 7.2 and 85(]SY.+-。[)2ﾟC.(1) Bulk genomic DNA in the siliceous deposit could be stably extracted using the lysozyme and freeze-thaw method. The volume of siliceous deposit formed on one copper plate and the amount of genomic DNA extracted from siliceous deposits was exponentially increased with the time of incubation.(2) The phylogenetic diversity in these DNA extracts was investigated by cloning and sequencing of partial 16S rRNA genes obtained by PCR.The bacterial community was composed mainly of three phylogenetic types in domain Bacteria. Cluster I (8 clones) was affiliated with the Aquificales and Cluster II (15 clones) was closely related to genus Thermus. Cluster III (2 clones), the sequences of which were homologous with Gram positive anaerobic thermophilic bacteria, was also detected.4.These extremely thermophilic bacteria may contribute to the rapid aggregation of amorphous silica and can probably serve as a parameter to determine the rate formation of siliceous deposit in the process of biomineralization. Less