Life in Extreme Environments/Early Life
David Fike, Washington University

Biogeochemistry is the study of the cycling of chemical elements and compounds between the living and nonliving parts of an ecosystem. The carbon and sulfur biogeochemical cycles play a predominant role in regulating Earth’s climate and redox conditions over geological time (GARRELS and LERMAN, 1981). Microbial ecosystems, through their metabolic activity and interconnected metabolic networks, have profoundly impacted Earth surface conditions over Earth history (RAYMOND and BLANKENSHIP, 2008). While we have no direct record of the earliest organisms, we have hints of their metabolic activity through geochemical and isotopic biosignatures preserved in ancient sediments dating back over 3 billion years (NEALSON & RYE, 2003). We can increase our understanding of these ancient ecosystems by investigating modern environments (e.g., hydrothermal systems, acidic lakes, anoxic fjords) that are geochemically similar to the conditions that are inferred to have characterized the early Earth (MARTIN et al., 2008). By investigating the metabolic and phylogenetic diversity in these modern “extreme” environments, we can piece together information about the functioning of the earliest ecosystems on the planet and how these ecosystems and metabolic networks have evolved in time along with the changing Earth.

References
Garrels, R. M. and Lerman, A., 1981. Phanerozoic cycles of sedimentary carbon and sulfur. Proceedings of the National Academy of Sciences USA 78.

Martin, W., Baross, J., Kelley, D., and Russell, M. J., 2008. Hydrothermal vents and the origin of life. Nature Reviews Microbiology 6, 805 - 814.

Nealson K. H. & Rye R. 2003. Evolution of metabolism. In: Schlesinger WH (ed) Treatise on Geochemistry, v. 8. Elsevier Science Limited, Amsterdam, pp 41-61.

Raymond, J. and Blankenship, R. E., 2008. The origin of the oxygen-evolving complex. Coordination Chemistry Reviews 252, 377 - 383.

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