DARK LIFE: THE SURPRISING MICROBIOLOGY AND GEOMICROBIOLOGY OF CAVE ENVIRONMENTS

Hypogenic caves represent a unique habitat in which to study microbial ecology: they lack photosynthetic energy input, are geologically isolated from other ecosystems, and are extremely limited in the nutrients that are essential to growth (carbon, nitrogen and phosphorous). Yet not only do caves contain a remarkable and varied microbial ecosystem, but their very geologic isolation allows us to examine processes that cannot be studied elsewhere. The absence of disturbance (such as diurnal, seasonal or meterological) allows us to study ecosystems that have been in equilibrium for thousands of years, while the geologic isolation preserves the remnants of microbial metabolic activity that surface weathering would either conceal or remove. Our work studying the microbial processes occurring within caves has revealed the critical role that microorganisms play in speleogenesis and mineral deposition, the unique nutrient scavenging systems that allow growth despite the extreme starvation, and revealed aspects of microbial evolution and physiology that would be impossible to study in surface ecosystems. Such work has also revealed that many geologic processes, once considered inorganic in nature, may actually be driven by microbial metabolic processes.