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Project Reports

• Biosignatures in Ancient Rocks

  The Biosignatures in Ancient Rocks group investigates the co-evolution of life and environment on early Earth using a combination of geological field work, geochemical analysis, genomics, and numerical simulation.

  ROADMAP OBJECTIVES: 1.1 3.2 4.1 4.2 4.3 5.1 5.2 5.3 6.1 6.2 7.1 7.2

• Survivability of Icy Worlds

  Survivability of Icy worlds (Investigation 2) focuses on survivability. As part of our Survivability investigation, we examine the similarities and differences between the abiotic chemistry of planetary ices irradiated with ultraviolet photons (UV), electrons, and ions, and the chemistry of biomolecules exposed to similar conditions. Can the chemical products resulting from these two scenarios be distinguished? Can viable microbes persist after exposure to such conditions? These are motivating questions for our investigation.

  ROADMAP OBJECTIVES: 2.2 3.2 5.1 5.3 7.1 7.2

• Ecology of Extreme Environments: Characterization of Energy Flow, Bioenergetics, and Biodiversity in Early Earth Analog Ecosystems

  The distribution of organisms and their metabolic functions on Earth is rooted, at least in part, to the numerous adaptive radiations that have resulted in the ability to occupy new ecological niches through evolutionary time. Such responses are recorded in extant organismal geographic distribution patterns (e.g., habitat range), as well as in the genetic record of organisms. The extreme variation in the geochemical composition of present day hydrothermal environments is likely to encompass many of those that were present on early Earth, when key metabolic processes are thought to have evolved. Environments such Yellowstone National Park (YNP), Wyoming harbor >12,000 geothermal features that vary widely in temperature and geochemical composition. Such environments provide a field laboratory for examining the tendency for guilds of organisms to inhabit particular ecological niches and to define the range of geochemical conditions tolerated by that functional guild (i.e., habitat range or zone of habitability). In this aim, we are examining the distribution and diversity of genes that encode for target metalloproteins in YNP environments that harbor geochemical properties that are thought to be similar to those that characterize early Earth. Using a number of newly developed computational approaches, we have been able to deduce the primary environmental parameters that constrain the distribution of a number of functional processes and which underpin their diversity. Such information is central to constraining the parameter space of environment types that are likely to have facilitated the emergence of these metal-based biocatalysts.

  ROADMAP OBJECTIVES: 3.2 3.3 3.4 4.1 4.2 5.1 5.2 5.3

• Biosignatures in Relevant Microbial Ecosystems

  PSARC is investigating microbial life in some of Earth’s most mission-relevant modern ecosystems. These environments include the extremely salty Dead Sea, the impact-fractured crust of the Chesapeake Bay impact structure, methane seeps on the ocean floor, deep ice in the Greenland ice sheet, and oxygen-free waters including deep subsurface groundwater. We target environments that, when studied, provide fundamental information that can serve as the basis for future solar system exploration. Combining our expertise in molecular biology, geochemistry, microbiology, and metagenomics, and in collaboration with some of the planet’s most extreme explorers, we are deciphering the microbiology, fossilization processes, and recoverable biosignatures from these mission-relevant environments.

  ROADMAP OBJECTIVES: 4.1 4.3 5.1 5.2 5.3 6.1 7.1 7.2

• Detectability of Life

  Detectability of Life investigates the detectability of chemical and biological signatures on the surface of icy worlds, with a focus on spectroscopic techniques, and on spectral bands that are not in some way connected to photosynthesis.Detectability of life investigation has three major objectives: Detection of Life in the Laboratory, Detection of Life in the Field, and Detection of Life from Orbit.

  ROADMAP OBJECTIVES: 1.2 2.1 2.2 4.1 5.3 6.1 6.2 7.1 7.2

• Mineralogical Traces of Early Habitable Environments

  The goal of our work is to understand how habitability (potential to support life) varies across a range of physical and chemical parameters, in order to support a long-term goal of characterizing habitability of environments on Mars. The project consists of two main components: 1. We are examining the interplay between physicochemical environments and associated microbial communities in a subsurface environment dominated by serpentinization (a reaction that involves water and crustal rocks, and which occurred on early Mars as indicated by observations of surface mineralogy). 2. We are working to understand how mineral assemblages can serve as a lasting record of prior environmental conditions, and therefore as indicators of prior habitability. This component directly supports the interpretation of mineralogy data obtained by the CheMin instrument on the Mars Science Laboratory.

  ROADMAP OBJECTIVES: 2.1 5.3

• Bacterial Steroids and Triterpenoids

  Methylococcus capsulatus is one of a handful of bacteria that are capable of producing both sterols and the sterol-like hopanoid lipids. In this project, we are studying the biosynthesis and function of both sterols and hopanoids of M. capsulatus in order to gain insight into the evolutionary and functional significance of these molecules in the bacterial domain.

  ROADMAP OBJECTIVES: 5.1 5.3

• Extremophile Ribosomes

  Diapausing embryos (resting eggs) from brachionid rotifers are able to withstand desiccation and thermal stress. Resting eggs can remain viable for decades, and develop normally once placed in a permissive environment that allows for hatching, growth and development. The exact mechanisms of resistance are not known, although several molecules have been suggested to confer protection during desiccation and thermal stress. In this study, we have identified by mass spectrometry two thermostable proteins, LEA (late embryogenesis abundant) and VTG (vitellogenin-like), found exclusively in the resting eggs of Brachionus manjavacas. This is the first observation that LEA proteins may play a role in thermostability and the first report of a VTG-like protein in the phylum Rotifera. These proteins exhibited increased expression in rotifer resting eggs when compared to amictic females. Our data suggest the existence of alternate pathways of desiccation and thermal resistance in brachionid rotifers.

  ROADMAP OBJECTIVES: 3.2 4.2 5.3

• Postdoctoral Fellow Report: Steven Mielke

  S. P. Mielke completed an NAI NASA Postdoctoral Program (NPP) fellowship during September 1, 2011 to February 29, 2012. His postdoctoral research has provided the basis for the project: “The Long-Wavelength Limit for Oxygenic Photosynthesis.” He continues this research as a Research Associate at Rockefeller University.

  ROADMAP OBJECTIVES: 3.2 4.2 5.1 5.3 6.2 7.2

• Stromatolites in the Desert: Analogs to Other Worlds

  In this task biologists go to field sites in Mexico to better understand the environmental effects on growth rates for freshwater stromatolites. Stromatolites are microbial mat communities that have the ability to calcify under certain conditions. They are believed to be an ancient form of life, that may have dominated the planet’s biosphere more than 2 billion years ago. Our work focuses on understanding these communities as a means of characterizing their metabolisms and gas outputs, for use in planetary models of ancient environments.

  ROADMAP OBJECTIVES: 4.1 4.2 5.2 5.3 6.1 6.2

• The Subglacial Biosphere – Insights Into Life-Sustaining Strategies in an Extraterrestrial Analog Environment

  Sub-ice environments are prevalent on Earth today and are likely to have been more prevalent the Earth’s past during episodes of significant glacial advances (e.g., snow-ball Earth). Numerous metabolic strategies have been hypothesized to sustain life in sub-ice environments. Common among these hypotheses is that they are all independent of photosynthesis, and instead rely on chemical energy. Recently, we demonstrated the presence of an active assemblage of methanogens in the subglacial environment of an Alpine glacier (Boyd et al., 2010). The distribution of methanogens is narrowly constrained, due in part to the energetics of the reactions which support this functional class of organism (namely carbon dioxide reduction with hydrogen and acetate fermentation). Methanogens utilize a number of metalloenzymes that have active site clusters comprised of a unique array of metals. During the course of this study, we identified other features that were suggestive of other active and potentially relevant metabolic strategies in the subglacial environment, such as nitrogen cycling. The goals of this project are 1) identifying a suite of biomarkers indicative of biological CH4 production 2). quantifying the flux of CH4 from sub-ice systems and 3). developing an understanding how life thrives at the thermodynamic limits of life. This project represents a unique extension of the ABRC and bridges the research goals of several nodes, namely the JPL-Icy Worlds team and the ASU-Follow the Elements team.

  ROADMAP OBJECTIVES: 2.1 2.2 5.1 5.2 5.3 6.1 6.2 7.1 7.2

• The Long Wavelength Limit for Oxygenic Photosynthesis

  Photosynthesis produces signs of life (biosignatures) on a planetary scale: atmospheric oxygen and the reflectance signature of photosynthetic pigments. Oxygenic photosynthesis is therefore a primary target in NASA’s search for life on habitable planets in other solar systems. An unanswered question is what the upper limit is to the photon wavelength at which oxygenic photosynthesis can remain viable. On other planets that have a parent star very different spectrally from our Sun, can we expect oxygen from plants of different colors from those on Earth?

  The cyanobacterium, Acaryochloris marina serves as a model organism for oxygenic photosynthesis adapted to low light and red-shifted light environments similar to what may be found on habitable planets orbiting M stars. Until A. marina was discovered in 1996, all known oxygenic photosynthesis relied on the pigment chlorophyll a (Chl a). A. marina instead uses chlorophyll d, which can absorb the far-red and near-infrared light in A. marina’s habitat. We use photoacoustics in the lab to measure the energy storage efficiency of A. marina with lasers, and molecular electrostatics modeling to surmise how replacement of Chl a by Chl d in A. marina affects arrangements within the photosystem molecules. We are finding that A. marina can perform oxygenic photosynthesis quite efficiently in its unique light niche.

  ROADMAP OBJECTIVES: 3.2 4.2 5.1 5.3 6.2 7.2

• Viral Ecology and Evolution

  This project is aimed at probing the occurrence and evolution of archaeal viruses in the extreme environments in the thermal areas in Yellowstone National Park. Viruses are the most abundant life-like entities on the planet and are likely a major reservoir of genetic diversity for all life on the planet and these studies are aimed at providing insights into the role of viruses in the evolution of early life on Earth.

  ROADMAP OBJECTIVES: 5.1 5.2 5.3 6.1 6.2

• Project 2F: Potential for Lithotrophic Microbial Oxidation of Fe(II) in Basalt Glass

  Ferrous iron (Fe(II)) can serve as an energy source for a wide variety of chemolithotrophic microorganisms (organisms that gain energy from metabolism of inorganic compounds). Fe(II) oxidation may have played a role in past (and possibly, present) life on Mars, whose crust is rich in primary Fe(II)-bearing silicate minerals, as well as Fe-bearing clay minerals formed during weathering of primary silicates. This project examined the potential for microbial oxidation of Fe(II) in basaltic glass. Recent research suggests that near‐surface hydrothermal venting may have occurred during past periods of active volcanic/tectonic activity on Mars. Such activities could have produced basalt glass phases that might have served as energy sources for chemolithotrophic microbial activity. Previous and ongoing NAI‐supported studies have shown that an established chemolithoautotrophic Fe(II)‐oxidizing, nitrate‐reducing culture can grow by oxidation of Fe(II) insoluble Fe(II)‐bearing phyllosilicate phases such as biotite and smectite. The initial goal of this project was to determine whether or not this culture is capable of oxidizing Fe(II) in basalt glass. In addition we tested basaltic glass oxidation by a culture of Desulfitobacterium frappieri, as previous studies demonstrated that D. frappieri is capable of nitrate-dependent oxidation of structural Fe(II) in smectite. Finally, in situ and enrichment culturing experiments were conducted to determine whether indigenous Fe(II)-oxidizing organisms in a groundwater iron seep were capable of colonization and oxidation of basaltic glass. The results of these experiments showed that while the various cultures were readily capable of smectite oxidation with nitrate, none were able to carry-out significant oxidation of Fe(II) in basalt glass. We speculate that Fe(II) atoms in the amorphous glass are somehow occluded and therefore not accessible to outer membrane cytochrome systems thought to be involved in extracellular Fe(II) oxidation.

  ROADMAP OBJECTIVES: 2.1 5.1 5.3

• Interdisciplinary Studies of Earth’s Seafloor Biosphere

  The remote deep sediment-buried ocean basaltic crust is Earth’s largest aquifer and host to the least known and potentially one of the most significant biospheres on Earth. CORK observatories have provided unparalleled access to this remote environment. They are enabling groundbreaking research in crustal fluid flow, (bio)geochemical fluid/crustal alteration, and the emerging field of deep crustal biosphere

  ROADMAP OBJECTIVES: 4.1 4.2 5.1 5.2 5.3 6.1 6.2 7.1 7.2

• Stoichiometry of Life – Task 1 – Laboratory Studies in Biological Stoichiometry

  This project component involves a diverse set of studies of various microorganisms with which we are trying to better understand how living things use chemical elements (nitrogen, phosphorus, iron, etc) and how they cope, in a physiological sense, with shortages of such elements. For example, how does the “elemental recipe of life” change when an organism is starved for phosphorus or nitrogen or iron? Is this change similar for diverse species of microorganisms? Furthermore, how does an organism shift its patterns of gene expression when it is starved by various nutrients? This will help in interpreting studies of gene expression in natural environments, including extreme environments relevant to astrobiology.

  ROADMAP OBJECTIVES: 5.2 5.3 6.1 6.2

• Measuring Interdisciplinarity Within Astrobiology Research

  To integrate the work of the diverse scientists working on astrobiology, we have harvested and analyzed thousands of astrobiology documents to reveal areas of potential connection. This framework allows us to identify crossover documents that guide scientists quickly across vast interdisciplinary libraries, suggest productive interdisciplinary collaborations, and provide a metric of interdisciplinary science.

  ROADMAP OBJECTIVES: 1.1 1.2 2.1 2.2 3.1 3.2 3.3 3.4 4.1 4.2 4.3 5.1 5.2 5.3 6.1 6.2 7.1 7.2

• Stoichiometry of Life, Task 2a: Field Studies – Yellowstone National Park

  Our stoichiometry studies are determining the relationships between the elemental compositions of organisms and the elemental compositions of their environments. We experimentally determine how changes in element availability (N, P, Fe) affect the community structure in hot spring ecosystems. We also use stable isotopes (¹⁵N and ¹³C) to trace which metabolisms actively utilize N and C and where in cells these elements are used. Recently, our team has shown for the first time that nitrogen (N₂) fixation can occur at temperatures >85oC (Loiacono et al. 2012). We are also developing robust environmental sensors for hot springs that reveal chemical and thermal gradients at scales similar to the observed spatial distributions in hot spring microbial communities.

  ROADMAP OBJECTIVES: 5.1 5.2 5.3 6.1 6.2 7.2

• Permafrost in Hawaii

  Permanent ice can be found on the Hawaiian Islands at extremely few locations and as a result of microclimates. Ice exists in the form of permafrost in craters near the summit of Mauna Kea and in form of ice lakes in lava tubes on Mauna Loa; they are the world’s most isolated ice caves. We investigate the microclimates on the high summits of the Hawaiian Islands that serve as possible analogues to Mars. Exploratory fieldwork has been carried out at four field sites and interdisciplinary collaborations have been developed.

  ROADMAP OBJECTIVES: 2.1 5.3 6.2

• Stoichiometry of Life, Task 2b: Field Studies – Cuatro Cienegas

  Cuatro Cienegas is a unique biological preserve in México (state of Coahuila) in which there is striking microbial diversity, potentially related to extreme scarcity of phosphorus. We aim to understand this relationship via field sampling of biological and chemical characteristics and a series of enclosure and whole-pond fertilization experiments. These studies help in identifying the element signatures that microbes develop when key nutrient elements are scarce. Furthermore, the chemical and physical environments of the desert aquatic habitats at Cuatro Cienegas are analogous to those that may have existed on Mars during times in its past when it was losing its own surface water. Thus, these data may help in interpreting information about element signatures obtained from the Curiosity rover as it explores Gale Crater.

  ROADMAP OBJECTIVES: 5.1 5.2 5.3 6.1 6.2

• Stoichiometry of Life – Task 2c – Field Studies – Other

  We continued analyses of organic matter in samples of porewaters from a deep ocean hydrothermal mound; concluded a study on element acquisition by biological soil crusts, and initiated a new study that may shed light on a recent hypothesis that floating pumice may have been a site for the origin of life. In this new study, the eruption of the Puyehue / Cordon Caulle volcano on 4 June 2011 near Bariloche, Argentina, provided a unique opportunity to investigate floating pumice as a unique habitat for microbial life. To assess this, we sampled floating pumice from various regional lakes to assess the make-up of the associated microbial communities using genomic techniques and to evaluate the use of key elements (nitrogen, phosphorus) by these microbes using chemical and isotopic methods.

  ROADMAP OBJECTIVES: 4.1 5.2 5.3 6.1

• Timescales of Events in the Evolution and Maintenance of Complex Life

  We are using natural occurring isotopes produced by long-lived radioactive decay to: provide high-precision dates on geological and biological processes and to trace the geochemical evolution of the oceans during key times in Earth history.

  ROADMAP OBJECTIVES: 4.1 5.3 6.1

• Stoichiometry of Life, Task 3b: Ancient Records – Genomic

  The goal of Task 3b is to bring the enormous and ever-increasing repository of genomic data, both from single organisms and natural environments, to bear on understanding the history of life on Earth. Team members bring together innovative, integrative methods for understanding the interaction and feedback between life and environment, in particular how nutrient and energy limitations shape evolution. These efforts are focused not only on ancient records, but also are playing an important role in understanding how life and environment co-evolve on the modern Earth.

  ROADMAP OBJECTIVES: 5.1 5.2 5.3

• Project 4E: Preliminary Studies of Fe Isotope Biogeochemistry in Fe-Rich Yellowstone National Park Hot Springs

  This preliminary project provided background information for future studies of the structure, function, and signatures (living and non-living) of Fe redox-based microbial life in the volcanic terrain of Yellowstone National Park (YNP). The focus on Fe redox-based systems stems from our expanding knowledge of the wide range of microbial energy metabolisms that are known to be associated with Fe redox transformations on Earth and potentially on other planets. Moreover, Fe redox transformations provide the potential for generation of mineralogical, isotopic, and organic biosignatures of past and present microbial life, which represent premier targets for testing the hypothesis that life currently exists or existed in the past on Mars. Preliminary data on Fe geochemistry and isotopic composition, and microbial community composition, was obtained for two contrasting Fe-rich springs in YNP: Chocolate Pots (CP), a warm, circumneutral environment that has formed on top of the Pleistocene-age Lava Creek Tuff, where a mixture of Fe-rich acid-sulfate geothermal fluids and neutral-pH groundwater from the Gibbon River catchment emerge to the surface; and The Gap site, a hot, acid-sulfate spring in the Norris Basin which supports active chemolithotrophic Fe(II) oxidation, analogous to other hot spring environments in YNP. The geochemical data demonstrated significant changes in aqueous Fe abundance and/or speciation along the flow paths at both sites, leading to accumulation of abundant Fe(III) oxides as well as aqueous Fe(III) at the acidic Gap site. A distinct separation in Fe isotope composition between aqueous Fe and deposited Fe(III) oxides (mainly amorphous Fe-Si coprecipitates) was also detected, with the oxide enriched in ⁵⁶Fe relative to ⁵⁴Fe as expected for redox-driven Fe isotope fractionation. However, the degree of fractionation was less the value of ca. 3 ‰ expected in closed system at isotope equilibrium. We suggest that internal regeneration of Fe(II) via dissimilatory Fe(III) reduction could enrich the aqueous Fe(II) pool in the heavy isotope, leading a much lower degree of Fe isotope fractionation – and hence a fundamentally different pattern of Fe isotope fractionation – than would occur in a strictly Fe(II) oxidation-driven reaction system. In support of this argument, an initial set of culturing experiments designed to recovery thermophilic Fe(III)-reducing organisms from CP and Gap materials resulted in the recovery of active Fe(III) reducers from both sites. In addition, preliminary pyrosequencing of ¹⁶S rRNA genes recovered from Gap solids provide evidence for Fe(III) reduction potential by the resident microflora. Particularly in the case of the Gap, sequences related to known Archaeal fermenters and elemental S/Fe(III) oxide reducers were abundant.

  ROADMAP OBJECTIVES: 2.1 5.1 5.3