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不均匀的，微生物发生的可变性不能简单地用细胞与矿物表面之间的静电相互作用来解释。一些研究表明，溶液化学、表面涂层和表面粗糙度等其他因素也会改变附着行为。PI先前对石油污染含水层中地下微生物定植的研究表明，微生物在不同矿物表面的原位分布部分与矿物的营养成分有关。微生物优先定植和破坏含有微量营养物质的硅酸盐矿物，如磷和铁，以微量磷灰石和铁氢氧化物的形式存在（Rogers等，1998;2001）。然而，目前尚不清楚附着点的矿物学是富含营养的包裹体还是硅酸盐基质。也不知道这些内含物是否只影响最初的附着，或者它们是否影响永久附着、随后的生长和定植以及表面蚀刻。本研究的目的是研究含营养物包裹体对微生物表面附着的影响。具体来说，本研究将研究长石中的磷灰石和氧化铁包裹体如何影响微生物附着。据推测，微生物会优先附着在这些包裹体的表面上，使硅酸盐接地块变得贫瘠。内含物可以通过增加表面电荷或对营养物或终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附着在组成不均匀的硅酸盐岩石上的特征。实验室实验将用于检查静态（无流动）条件下的附着力，并将近似“最大”初始附着力。纯菌株培养，包括金属还原地杆菌和产甲烷菌和原生厌氧菌群，将用于实验中，以表征由于特定类型的相互作用、竞争和/或共生而导致的附着行为的任何变化。这些实验中使用的固相将包括含有P和Fe矿物包裹体的长石，以及不含这些营养相的对照物。耐热玻璃还将生产含有分散的P和Fe以及含P和Fe矿物的玻璃。玻璃将充当“人造”岩石，用来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，细胞是否普遍存在斑点行为。对于所有的附着实验，下伏的地表矿物学/成分将被映射并与附着模式相关联。最后，使用同一套固体的现场微观环境将与本地财团在原位反应。假定微生物附着在矿物表面是发生大量矿物蚀刻所必需的，现场结果将用于将附着与原位观察到的微生物风化过程联系起来。

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.