Themes and Sessions

16a: Microbial Cycling of Toxic Elements (eg. As, Se, Hg, Te) in Extreme Environments
Convenors: Tamar Barkay, Andreas Kappler
Keynote: Jonathan Lloyd (University of Manchester)
Orals: Mon PM
Posters: Thu AM
Microbial interaction with toxic elements is a well developed field of research due to the toxicity of these elements to living organisms. This topic is of particular interest to microbial ecologists and geologists as toxic elements impact microbial community structure and function and microbes affect the redox state and chemical properties of the elements. While research on microbe-toxic elements interactions have progressed for decades, the study of these interactions in extreme environments has only recently begun, even though such environments are often characterized by elevated concentrations of such elements. Thus, microbes and communities in environments characterized by high temperature and salinity and low pH have been exposed to toxic elements throughout the course of their evolution. This long term relationships imply that (i) novel modes of microbial interactions with toxic elements may be found in extreme environments, and (ii) the evolutionary origin for the mechanisms that govern toxic element transformations might be found in extreme environments. This session will be comprised of presentations that summarize current studies that address these issues.
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16b: Pathways and Regulation of Energy and Carbon Transfer in Deep-Sea Extreme Environments
Convenors: Stefan Sievert, Nadine Le Bris
Keynote: Costantino Vetriani (Rutgers University)
Orals: Tue AM
Posters: Thu PM
Some of the most extreme environments on Earth are found in the deep-ocean (hydrothermal vents, methane and hydrocarbon seeps, hypersaline lakes). They exhibit tremendous variability in a number of physico-chemical parameters, including temperature, pH, gas (H₂S, CO₂, CO, O₂) and heavy metal concentrations, and other potentially harmful chemicals. Yet they are among the most productive marine environments. Key processes sustaining deep-sea chemosynthetic communities have been highlighted (chemolithoautotrophy, symbiosis) but the wide range of biogeochemical pathways arising from the variety of redox conditions, and the complexity of energy transfer mechanisms from molecules to organisms remain to be described. Availability of chemical substrates and energy budgets, diversity of carbon fixation pathways, adaptability of symbioses, interactions between invertebrates and biogeochemical processes, and large-scale impact of these processes are major issues for which recent interdisciplinary studies and new analytical capabilities have allowed significant advances. These new insights provide a better understanding of the underlying mechanisms sustaining the high productivities of these ecosystems and their potential impact on global element cycling.
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16c: Production and Consumption of Methane and Higher Alkanes in Extreme Environments
Convenors: Samantha (Mandy) Joye, Jean-Luc Charlou
Keynotes: Alexander Bradley (Harvard University) , Katharina Ettwig (Radboud University Nijmegen)
Orals: Mon AM
Microbially-mediated production and/or consumption of methane and higher alkanes occurs, often at high rates, in a variety of extreme environments, including cold seeps, hydrothermal vents, terrestrial hot springs, and saline lakes. The alkanes in such systems are derived from either microbial, thermogenic or abiogenic processes. Alkane cycling often involves complex microbial communities which may foster interactions between alkane consuming microbiota and partner microorganisms. The emission of alkanes, especially methane, from aquatic habitats can impact on global climate, making this a topic of widespread interest. This session will bring together are microbiologists, biogeochemists, and modelers to describe the patterns and controls of alkane cycling in extreme environments with the hope of identifying patterns and themes that occur across systems.
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16d: Exobiology: Are any Terrestrial Extremophiles Plausible Proxies for Hypothesized Microbial Life on Venus, Mars, or the Jovian Planets and their Satellites (E.g., Titan, Europa, Callisto, Enceladus)?
Convenors: Mary Voytek, David DesMarais
Keynote: David Des Marais (NASA Ames Research Center)
Orals: Mon PM
Posters: Thu PM
Investigations of contemporary microbial communities can guide our exploration of Earth's early biosphere as well as our search for life elsewhere in the solar system. Life as we know it requires liquid water. Evidence for the presence or past activity of water has been detected on several planetary bodies besides Earth. Accordingly our search for signs of past or present life elsewhere in the Solar System is enhanced by studies of the biogeochemistry, microbiology and biosignatures of extreme environments on Earth such as those in the subsurface, in hot springs and in frozen deposits. Recent Mars missions are providing additional clues to help focus such Earth-based studies. This session explores a broad range of topics including prebiotic chemical evolution, quantifying the habitability of environments, biogeochemical cycles, biosignatures, and the roles played by mineralization in biological evolution and the preservation of biosignatures.
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16e: Biogeochemistry and Biology of CO₂ and pH Extremes
Convenors: Antje Boetius, Fumio Inagaki
Keynote: James P. Barry (MBARI)
Orals: Wed AM
Posters: Thu AM
Among the different extreme environments on Earth, those varying in CO₂ concentration pose a variety of challenges for different life forms. In this session, we would like to invite presentations dealing with field based and experimental studies on aquatic/sedimentary ecosystems and biogeochemical functioning under CO₂ and pH extremes. How are CO₂ concentrations and corresponding pH levels affecting the habitability of an ecosystem? What are threshold levels for changes in organism performance, community structure, biodiversity, and metabolic functioning? By which mechanisms can organisms adapt to or counteract the effect of CO₂ and pH extremes? What are the peculiarities of carbon cycling and other biogeochemical processes in such extreme environments? One focus of the session will be how extreme CO₂ and pH environments can serve as natural analogues, e.g. acidic CO₂ vents for CO₂ leakage from carbon dioxide capture and storage in the terrestrial subsurface and/or deep-sea, or for different levels of ocean acidification; and high pH vents for unique carbonate habitats for microbial life formed by serpentinization.
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16f: Life in the Deep Dark Subsurface Biosphere
Convenors: Peter Girguis, Julie Huber
Keynote: Everett Shock (Arizona State)
Orals: Tue PM
Posters: Thu PM
Recent studies show that oceanic crust and sediments host extensive but poorly characterized microbial communities. Data suggest these are the largest microbial communities on Earth, and accordingly, there is continuing debate about the extent and impact of this deep biosphere. This session will examine these issues, highlighting results of novel and interdisciplinary approaches to studying the subsurface biosphere, and examining the role of interdisciplinary approaches to studying microbial processes. This session will specifically focus on the recent and significant advances that provide insight into the physiological potential and activity of these communities. These and other findings have been enabled by recent advances in techniques and technologies, from metagenomics to bioenergetic modeling, and will constitute the basis of our discussion.
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16g: You Call This a Living?: The Microbial Ecology and Biogeochemistry of the Atacama Desert and Antarctic Dry Valleys
Convenors: Brent C. Christner, Jacek Wierzchos
Keynote: Alison E. Murray (Desert Research Institute)
Orals: Tue PM
This session will lay emphasis on new research conducted in two of the driest regions on Earth. Life requires liquid water as a solvent for biochemical reactions, for mass transfer, and to establish electrochemical gradients. High solute concentrations, absorption of water to solid surfaces, and subfreezing temperatures are all factors that result in decreased water activity. As such, studies of microorganisms and communities inhabiting temperate and polar deserts provide model systems for examining the limits of microbial metabolism under conditions of low water availability. An overarching goal of this session is to connect common microbial strategies for survival in these seemingly disparate environments.
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17j: The Genomics of Geochemistry
Convenor: Greg Dick
Keynote: Kenneth Nealson (University of Southern California)
Orals: Thu AM
Posters: Wed AM
The availability of thousands of microbial genome sequences and a growing number of metagenomes is opening new views into how and why microorganisms drive elemental cycles. However, significant challenges remain in interpreting this data and translating it into geochemical implications. This session will highlight how genomics is transforming our understanding of microbial biogeochemistry, not only through sequencing of single organisms but also sequencing of mixed communities (metagenomics) and via methods such as transcriptomics and proteomics that address genome dynamics. Contributions that intimately link these emerging approaches to biogeochemical processes are encouraged.
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19i: Bioenergetics in Geochemical Modeling
Convenors: Doug LaRowe, Andy Dale
Keynote: Qusheng Jin (University of Oregon)
Orals: Thu PM
Posters: Wed AM
Biogeochemical reactions are often described in geochemical reaction-transport models using kinetic terms that have Monod-style hyperbolic expressions for promotion or inhibition of microbially-mediated reaction pathways. However, there is a growing interest in developing more rigorous thermodynamically based approaches to describe which processes dominate in coupled biogeochemical reaction networks. On such approach involves the hypothesis that a particular metabolic reaction is catalyzed only when the available Gibbs energy in a given environment exceeds the energy required to synthesize biochemical energy in the form of ATP. Furthermore, the fact that the energy requirements for a variety of microbes and the terminal electron acceptors that they use differ suggests that the extent of the thermodynamic driving force on rates of reaction rates is also likely to vary. This session will survey the current state-of-the-art of the treatment of thermodynamics in biomass-explicit and –implicit microbially-mediated reaction networks and consider the possibilities for developing more nearly universal biogeochemical rate laws which can be incorporated into geochemical models.
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