Microbial Ion Accumulation and Mineral Formation in the Weathering Environment

细菌是地球上最早的生命，出现在地球历史的第一个十亿年。从那时起，细菌已经广泛分布在地球表面，包括土壤，风化岩石和沉积物，湖泊，河流和海洋。地球生物学研究表明，细菌在地球表面的元素循环中起着重要作用，特别是通过细胞壁表面与外部环境中溶解的离子相互作用，产生各种次生矿物，如氧化物，硫化物，碳酸盐和硅酸盐。本研究利用XRD、SEM、TEM和EDX等方法，对分布于日本九州南部鹿儿岛县的各种风化沉积物（伊藤火山碎屑流存款、赤穗屋火山灰存款、海门岳火山灰存款、樱岛火山灰存款）中的细菌-矿物相互作用进行了研究。本研究的结果表明，这些风化沉积物含有大量的球形至杆状细菌（10^7 <$10^8个细胞/g），这些细菌被无序的次生矿物覆盖或装饰，表现出细纤维材料的聚集体。能谱分析表明，次生矿物主要由铝、硅、铁组成，其化学成分介于水铝英石、绿脱石和硬绿泥石之间。这些化学特征明显不同于与细菌表面产物共存的无机次生产物水铝英石和埃洛石。这强烈地表明，风化沉积物中的大多数细菌积累Al、Si和Fe离子，并在其细胞表面产生硅酸盐矿物。

Bacteria are the earlist life of the Earth, appearing within the first billion years of the Earth's history. Scince then, bacteria have been widely distributed on the Earth's surface including soils, weathered rocks and sediments, lakes, rivers, and oceans. Geobiological studies have shown that bacteria play an important role in elemental circulation over the Earth's surface, especially through the interactions of cell wall surfaces with dissolved ions in the external environments producing various secondary minerals such asoxides, sulfides, carbonates, and silicates. This study focused on such bacteria - mineral interaction in various weathered sediments (Ito pyroclastic fllow deposit, Akahoya volcanic ash deposit, Kaimondake volcanic ash deposit, Sakurajima volcanic ash deposit) distributed in Kagoshima prefecture, Southern Kyushu, Japan, using XRD, SEM, TEM, and EDX. Results of this study indicated that these weathered sediments contain great amounts of spherical to rod-shaped bacteria (10^7〜10^8 cells/g) covered or decorated with poorly ordered secondary minerals exhibiting aggregates of fine fibrous materials. EDX confirmed that the secondary minerals consisted mainly of Al, Si, and Fe, corresponding to chemical compositions among allophane, nontronite, and chamosite. These chemical characteristics are apparently different from those of abiogenie secondary products such as allophane and halloysite co-existing with the products on the bacterial surfaces. This strongly indicates that the most of bacteria in the weathered sediments acculucate Al, Si, and Fe ions and produce silicate minerals on their cell surfaces.