Microscale Mineralogic Controls on Microbial Attachment to Rock Surfaces: Implications for Microbial Mineral Dissolution

微生物普遍存在于浅层地下，附着在沉积物表面和水相中。当附着时，微生物可以改变附着点的地球化学微环境，改变矿物平衡并驱动风化反应。然而，沉积物颗粒上的微生物附着是异质的，微生物发生的变异性不能简单地用细胞和矿物表面之间的静电相互作用来解释。一些研究表明，其他因素，如溶液化学，表面涂层和表面粗糙度可以改变附着行为。PI先前对石油污染含水层地下微生物定植的研究表明，微生物在不同矿物表面的分布在原位，部分，微生物优先定植并破坏含有有限微量营养素的硅酸盐矿物，如P和Fe，以痕量磷灰石和羟基氧化铁的形式存在（Rogers等人，1998; 2001）。然而，目前尚不清楚附着点的矿物学是富含营养物的包裹体还是硅酸盐基质。也不知道，如果这些夹杂物的影响，只有最初的附件，或者如果他们影响永久性的附件，随后的增长和殖民化，和表面etching.The拟议的研究的目标是研究的营养矿物夹杂物对微生物表面附着的影响。具体来说，这项研究将探讨磷灰石和氧化铁夹杂物中的磷灰石影响微生物附着。据推测，微生物将优先附着在这些夹杂物的表面表达，使硅酸盐基质贫瘠。包裹体可能通过增加表面电荷或对营养物或末端电子受体的趋化行为来增加附着。拟议的研究将使用实验室实验来表征微生物对成分不均匀的硅酸盐岩石的附着。实验室实验将用于检查静态（无流动）条件下的附着，并将接近“最大”初始附着。纯菌株培养物，包括Geelimetallireducens和Methanosaeta concilii和天然厌氧聚生体，将用于实验中，以表征由于类型特异性相互作用、竞争和/或共生引起的附着行为的任何变化。在这些实验中使用的固相将包括含P和Fe矿物夹杂物的菱镁矿，以及没有这些营养相的对照。高硼硅玻璃还将生产含有分散的磷和铁以及包括磷和铁矿物的玻璃。玻璃将作为“人造”岩石，以测试细胞是否优先附着在内含物上，或者当营养物质分散时，斑块行为是否普遍。对于所有附着实验，将绘制底层表面矿物学/成分图并将其与附着模式相关联。最后，使用同一套固体的现场微观世界将与本地财团原位反应。据推测，微生物附着到矿物表面是必要的大量的矿物蚀刻发生，和现场的结果将被用来连接到微生物风化过程中观察到的原位附着。

Microorganisms are ubiquitous in the shallow subsurface, attached to sediment surfaces and in the aqueous phase. When attached, microorganisms can alter the geochemical microenvironments at the point of attachment, shifting mineral equilibria and driving weathering reactions. However, microbial attachment on sediment grains is heterogeneous and the variability of microbial occurrence cannot be simply explained by electrostatic interactions between the cell and the mineral surface. Several studies have shown that other factors such as, solution chemistry, surface coatings, and surface roughness can change attachment behavior.Previous research by the PI on subsurface microbial colonization in a petroleum-contaminated aquifer suggests that the distribution of microorganisms on different mineral surfaces in situ is related, in part, to the nutrient content of the mineral. Microorganisms preferentially colonize and destroy silicate minerals that contain limiting trace nutrients, such as P and Fe, occurring as trace apatite and iron oxyhydroxides (Rogers et al., 1998; 2001). It is still unclear, however, whether the mineralogy of the point of attachment is nutrient-rich inclusion or silicate matrix. Nor is it known if these inclusions impact only initial attachment, or if they influence permanent attachment, subsequent growth and colonization, and surface etching.The goal of the proposed research is to study the influence of nutrient-bearing mineral inclusions on microbial surface attachment. Specifically, this study will examine how apatite and iron oxide inclusions in feldspars influence microbial attachment. It is hypothesized that microorganisms will preferentially attach to surface expressions of these inclusions leaving the silicate groundmass barren. Inclusions may increase attachment through increased surface charge or chemotactic behavior to nutrients or terminal electron acceptors.The proposed research will use laboratory experiments to characterize microbial attachment to silicate rocks that are compositionally heterogeneous. Laboratory experiments will be used to examine attachment under static (no-flow) conditions and will approximate "maximum" initial attachment. Pure strain cultures, including Geobacter metallireducens and Methanosaeta concilii and native anaerobic consortia will be used in experiments to characterize any changes in attachment behavior due to type-specific interactions, competition, and/or symbiosis. The solid phases used in these experiments will consist of feldspars containing inclusions of P and Fe minerals, as well as controls without these nutrient phases. Pyrex glasses will also be manufactured containing dispersed P and Fe as well as, included P and Fe minerals. Glasses will serve as "artificial" rocks to test whether cells preferentially attach to inclusions or if patchy behavior is prevalent when nutrients are dispersed. For all attachment experiments the underlying surface mineralogy/composition will be mapped and correlated to attachment patterns. Finally, field microcosms using the same suite of solids will be reacted with the native consortia in situ. It is assumed that attachment of microbes to mineral surfaces is necessary for substantial mineral etching to occur, and field results will be used to link attachment to microbial weathering processes observed in situ.