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Project Reports

• Life Underground

  Our multi-disciplinary team from the University of Southern California, California Institute of Technology, Jet Propulsion Lab, Desert Research Institute, Rensselaer Polytechnic Institute, and Northwestern University is developing and employing field, laboratory, and modeling approaches aimed at detecting and characterizing microbial life in the subsurface—the intraterrestrials. We posit that if life exists, or ever existed, on Mars or other planetary body in our solar system, evidence thereof would most likely be found in the subsurface. This study takes advantage of unique opportunities to explore the subsurface ecosystems on Earth through boreholes, mine shafts, sediment coring, marine vents and seeps, and deeply-sourced springs. Access to the subsurface—both continental and marine—and broad characterization of the rocks, fluids, and microbial inhabitants is central to this study. Our focused research themes require subsurface samples for laboratory and in situ experiments. Specifically, we are carrying out in situ life detection, culturing and isolation of heretofore unknown intraterrestrial archaea and bacteria using numerous novel and traditional techniques, and incorporating new and existing data into regional and global metabolic energy models.

  ROADMAP OBJECTIVES: 2.1 2.2 3.1 3.2 3.3 4.1 5.1 5.2 5.3 6.1 6.2 7.2

• Inv 1 – Geochemical Reactor: Energy Production at Water-Rock Interfaces

  INV 1 examines water-rock interactions in the lab and in the field, to characterize the geochemical gradients that could be present at water-rock interfaces on Earth and other worlds, taking into account different ocean and crustal chemistries. We have fully investigated serpentinization as the most likely of all possible environments for life’s emergence on Earth as well as other water-rich worlds – a key goal for astrobiology as stated in the NASA Astrobiology Roadmap 2008. (Russell, 2015). Serpentinization is now recognized as fundamental to delivering the appropriate chemical disequilibria at the emergence of life. And the fact that this process is likely inevitable on any icy, wet and rocky planet makes its study fundamental to emergence of life, habitability and habitancy. Nevertheless, notwithstanding the thermodynamic drives to CO₂ reduction during the process, great uncertainty exists over just what kind of organic molecules (if any) are delivered to the submarine springs and consequential precipitate mounds. In attempts to clarify what these might be we have undertaken thermodynamic modelling and experimental investigations of the serpentinization process.

  ROADMAP OBJECTIVES: 2.2 3.1 3.2 3.3 3.4 4.1

• Project 2: Cells as Engines and the Serpentinization Hypothesis for the Origin of Life

  All life is, and must be, “powered” since all of its most essential and distinguishing processes have to be driven “up-hill” against their natural thermodynamic direction. By the 2nd law of thermodynamics, however, a process can only be made to proceed up-hill by being mechanistically linked, via a molecular device functioning as an engine, to another, more powerful, process that is moving in its natural, down-hill direction. On fundamental principles, we argue, such engine-mediated conversion activities must also have been operating at, and indeed have been the cause of, life’s emergence. But what then were life’s birthing engines, what sources of power drove them, what did they need to produce, and how did they arise in an entirely lifeless world? Promising potential answers to these and other questions related to the emergence of life are provided by the Alkaline Hydrothermal Vent/serpentinization (“AHV”) hypothesis, whose original propounder and lead proponent, Dr. Michael Russell of JPL, is a co-investigator on this project. The goal of the project is specifically to clarify the essential mechanistic modus operandi of all molecular engines that power life, and to see how the most fundamental and prerequisite of these could have arisen, and operated, in the structures and flows produced by the serpentinization process. Importantly, candidate answers to these questions can be put to definitive laboratory tests.

  ROADMAP OBJECTIVES: 1.1 1.2 3.1 3.2 3.3 3.4

• Inv 2 – From Geochemistry to Biochemistry

  INV 2 focuses on experimentally simulating the geological disequilibrium in hydrothermal systems, and determining the role of minerals in harnessing these gradients toward the emergence of metabolism. Biology utilizes metals (to speed up reactions) and “engines” (such as electron bifurcators, to couple endergonic and exergonic reactions); these components in modern metabolism strongly resemble specific minerals found in hydrothermal environments. We focus on simulating these primordial geological components and processes that might have led to the beginning of metabolism in a seafloor system on a wet rocky planet.

  ROADMAP OBJECTIVES: 3.1 3.2 3.3 4.1 7.1

• Project 4: Co-Evolution of Escherichia Coli and Its Parasite Bdellovibrio Bacteriovorus: An Experimental Model for Eukaryogenesis

  This project seeks to address a long-standing question in the early evolution of life on Earth: how and why did simpler cell types (prokaryotes) transition into more complex (eukaryotic) cells (i.e. eukaryogeneis)? Because this conversion happened millions of years ago and left scant fossil evidence, we have been attempting to “re-create” a similar transformation in the lab that can be easily manipulated and studied in detail. A greater understanding of the events that ocurred both before and after eukaryogenesis will not only help NASA scientists predict what extraterrestrial life might look like, it will also help us understand how modern eukaryotic cells function and evolve.

  ROADMAP OBJECTIVES: 3.3 3.4 5.1 6.2

• High Temperature W/R Hosted Microbial Ecosystems in Yellowstone

  Geochemical data indicate that life on early Earth was dependent on chemical forms of energy. This attribute, when coupled with phylogenetic data indicating that early evolving forms of life were thermophilic, lead many astrobiologists to believe that life evolved in a high temperature environment and was dependent on chemical forms of energy to sustain its metabolism.

  Hydrothermal environments with temperatures >70ᵒC exclude life dependent on light energy, leaving only those life forms that can sustain themselves using chemical energy. The >14,000 hot springs in Yellowstone National Park therefore provide a unique field-based early Earth analog environment to examine the processes that sustain life dependent on chemical energy and to investigate the metabolic processes that sustain this life. Moreover, the chemical and physical variation present in these environments affords the opportunity to examine how this variation drove the diversification of life in these early Earth analog environments. RPL investigations in hot spring environments in Yellowstone in 2015 centered on answering questions related to the array of energy and carbon sources available to chemosynthetic life, the preferred carbon sources supporting this life, and the role of hydrogen transformation in the metabolisms of these organisms. By answering these interrelated questions, we will provide a framework by which we can use to begin to understand the processes that most likely sustained microbial life on the early Earth. Since it is possible, if not likely, that such processes would also sustain early life on other planetary bodies, this research has the potential to guide the search for life in non-Earth environments.

  ROADMAP OBJECTIVES: 3.2 3.3 4.1 5.2 5.3 6.1

• Project 7: Mining Archaeal Genomes for Signatures of Early Life: Comparison of Metabolic Genes in Methanogens

  Methanogens represent the largest diversity among the archaea and have the unique ability to generate methane from simple compounds such as carbon dioxide, acetate and methylamines which were common in the anaerobic environments of early Earth and perhaps Mars. Methane biosynthesis also requires the presence/uptake of important ions such as sulfates, sulfides, carbonates, phosphates, and various light metal ions. In this project, we are attempting to analyze the evolution of the methanogens’ central cellular functions of translation, transcription, replication, and metabolism. To accomplish this, we are constructing the metabolic and regulatory networks of Methanosarcina acetivorans, the most complex methanogen known, and using these models to establish a framework for studying the evolution of methanogens. Results will be tested through microfluidic studies using varying carbon and ion sources.

  ROADMAP OBJECTIVES: 1.1 2.1 3.1 3.2 3.3 3.4 4.1 4.2 5.1 5.2 5.3 6.1 6.2 7.1

• Physiology of Microbial Populations From W/R Hosted Ecosystems

  Microbial communities supported by chemical energy (chemotrophic communties) released through water / rock interactions are widespread in contemporary Earth environments, including the subsurface where light is excluded and in surface environments where physical or chemical conditions preclude photosynthetic metabolisms. Chemotrophic microorganisms are key targets of astrobiological investigation due to the strong likelihood that they predate photosynthetic metabolisms and because they can be physiologically tested to define the habitable limits for life on Earth, including those associated with extremes of temperature, pH, salinity, and energy availability. Research by RPL scientists is focused on identifying and characterizing the physiological strategies or mechanisms that allow life to persist under extreme conditions at the habitable limits. By combining this information with phylogenetic approaches, we aim to determine how and when these mechanisms evolved and what role they played in the diversification of early life. As such, this research effort is highly interdisciplinary and employs both traditional (e.g., activity assays, cultivation) and contemporary (genomics, transcriptomics, metabolomics) microbiological approaches in combination with geochemical approaches. In addition, RPL investigators are studying the evolution of these communities to hone in on the nature of key physiological processes (e.g., central carbon metabolism, nitrogen metabolism, and iron-sulfur metabolism) in chemotrophs prior to the onset of photosynthetic metabolisms. Field-based RPL investigations of microbial physiology in water/rock ecosystems to date have focused on populations inhabiting subglacial environments (cold-adaptation), hot springs (adaptation to acidity, high temperature), and subsurface peridotite environments (adapation to energy stress, nutrient stress, alkalinity).

  ROADMAP OBJECTIVES: 3.1 3.2 3.3 4.1 5.1 5.2 5.3