PROBING THE EVOLUTION OF MICROBE-MINERAL INTERFACES IN ROCK-DOMINATED SYSTEMS

The activity of microbial organisms has profoundly affected the chemistry of the Earth's surface through at least the past 3.8 billion years. There is growing evidence that microbes sense and specifically interact with minerals of differing surface structure and chemical composition. This leads to preferential mineral colonization and dissolution, and the formation of mineral products not predicted from known reaction pathways. In turn, changes in mineralogy and surface chemistry trigger changes in the microbial community composition and modes of microbial growth, resulting in a complex co-evolution of biogeochemical systems over time. Remarkably, many controls and feedbacks between microbial activity and mineral chemistry remain unexplored. One of the major challenges in this area of research is the development of appropriate tools that can interrogate these interfaces at the molecular level. However, using a variety of surface-sensitive x-ray spectroscopic techniques, we can successfully elucidate how bacterial and mineral surfaces, and the complex interfaces between them, control the chemical dynamics of metals in the environment. From a biological perspective, one of the most important questions to be addressed is how fluids and rocks interact to form the basis for life throughout the subsurface of the earth. Yet by identifying the molecular mechanisms whereby microbial organisms harness solid-phase sources of energy, we may define one of the most common modes of metabolism in modern and ancient rock-dominated systems.