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Executive Summary

Project Summary

Low temperature is a predominant environmental characteristic of interstellar space, our solar system, including most of the planets and their satellites, and asteroids and meteors. An understanding of the impact of low temperatures on the responses and evolution of biological organisms is, thus, integral to our knowledge of Astrobiology. The research that we propose will explore multiple aspects of microbial adaptation to low temperatures. One major line of investigation will be to conduct structural and functional genomic and proteomic analyses of bacteria that have been isolated from the Arctic and Antarctic permafrost. What genes and proteins enable the permafrost bacteria to inhabit these subfreezing environments? Do they have specific “freezing tolerance” genes and proteins, or “specialized alleles” of commonly found bacterial genes, or both? How is expression of the bacterial genome affected by low temperatures and other conditions that “hitchhiker” bacteria might encounter during travel through space on natural objects or spacecraft? In a second line of investigation, we will directly examine, through “test-tube evolution” experiments, bacterial adaptation to low temperatures. The studies will provide insight into how an organism, with a given complement of genes, can cross niche barriers that are defined by decreasing temperatures. And finally, we will use the information gained to explore the potential development of “signatures” for the presence of life in cold environments including Earth and other bodies such as Mars and Europa.

The proposed studies will provide significant new information relating to multiple goals outlined in the “Astrobiology Roadmap” including: Explore how life evolves on the molecular, organism and ecosystem levels (goal 3); Determine how the terrestrial biosphere has co-evolved with the Earth (goal 4); Establish limits for life in environments that provide analogues for condition on other worlds (goal 5); Determine how to recognize the signature of life on other worlds (goal 7); and Understand the response of terrestrial life to conditions in space or on other planets (goal 10). Moreover, the proposed studies address one of the perceived gaps in the current NAI research program, namely, “provide understanding of the response of life to the space environment, from gene expression to microbial evolution.” Finally, there are significant potential practical applications of the work ranging from the identification of genes that may be used to confer improved environmental stress tolerance in crop plants to the discovery of enzymes uniquely suited to catalysis at low temperature, a characteristic of importance in numerous biotechnology applications.

The proposed lines of interrelated investigations call for a broad range of expertise. Consequently, we have assembled a group of investigators with diverse backgrounds, training and research interests. The areas of expertise include microbial ecology (Tiedje, Sepulveda), the isolation and characterization of permafrost bacteria (Gilichinsky, Tiedje), permafrost geology and geochemistry (Gilichinsky), molecular genetics and gene regulation (Kathariou, Thomashow), evolution and population genetics (Lenski, Bennett), cryobiology and mechanisms of freezing tolerance (McGrath, Thomashow), proteomics and protein evolution (Lubman, Goldstein), and structural genomics (Branscomb, Hawkins, Predki). As the proposed lines of research develop, we anticipate that the Center will evolve, bringing in new investigators to provide expertise to attack the next generation of questions. For instance, the structural genomic and gene expression profiling studies will lead to lines of investigation focused on specific genes with the objectives of establishing their roles in cold tolerance; determining their modes of action; and developing hypotheses as to how the genes evolved. While the current Center investigators are well qualified to conduct these lines of research, it may, perhaps, become evident that adding an investigator with expertise in using X-ray crystallography and/or NMR-spectroscopy to determine protein structure-function relationships would strengthen the research efforts.

We also envision that additional lines of investigation will evolve out of our interactions with researchers in other Centers of the Astrobiology Institute. For instance, among our objectives are to conduct experiments to determine how bacterial gene expression and evolution are affected by conditions that relate to the space environment. Our major focus will be on cold temperatures. However, it seems likely that it would be of interest and importance to other Center members to understand how microorganisms react, in terms of gene expression and evolution, to other environmental conditions of space such as the Martian atmosphere and regolith or perhaps microgravity and solar radiation. We view the defining of mutual research interests and development of collaborative Center research efforts to address fundamental questions in astrobiology to be an underlying goal of our program.