Endolithic microbial ecosystems: Molecular phylogenetic composition, ecology and geobiology
Endolithic ecosystems were studied from three distinct areas: the Rocky Mountain region and Yellowstone National Park of the USA, and Shark Bay in Western Australia. Morphologically similar to endolithic communities from previous studies, Rocky Mountain communities provide insight into endolithic ecology. Novel endolithic communities were discovered in Yellowstone geothermal environments. Electron microscopic analysis indicated Yellowstone communities are subject to mineralization and fossilization. Remnants of such fossils might provide clues about ancient life analogous to those provided by fossil stromatolites, structures preserved throughout much of the & sim;4 billion year geological record and considered analogs of a few extant examples. Stromatolites have been popularly considered geological evidence for oxygenic photosynthesis. Here I present the first comprehensive analysis of living Shark Bay stromatolite communities. Results suggest microorganisms other than cyanobacteria dominate these communities and probably contribute to their formation. Therefore, fossil stromatolites cannot be taken alone as evidence for oxygenic photosynthesis. Phylogenetic and statistical comparison of endolithic communities from this study and a previous study of Antarctic communities help support the principle that patterns of microbial diversity are governed by similar principles observed in macro-ecological systems. Results also provide insight into geobiological processes that shape the biosphere and help us understand the history of life on Earth and possibly elsewhere in the Solar System.