|C-DEBI Newsletter – September 1, 2015
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Frontiers in Microbiology
Carbon fixation by basalt-hosted microbial communities
Beth N. Orcutt*, Jason B. Sylvan*, Daniel Rogers, Jennifer Delaney, Raymond W. Lee, Peter R. Girguis*
*C-DEBI Contribution 277
Oceanic crust is a massive potential habitat for microbial life on Earth, yet our understanding of this ecosystem is limited due to difficulty in access. In particular, measurements of rates of microbial activity are sparse. We used stable carbon isotope incubations of crustal samples, coupled with functional gene analyses, to examine the potential for carbon fixation on oceanic crust. Both seafloor-exposed and subseafloor basalts were recovered from different mid-ocean ridge and hot spot environments (i.e., the Juan de Fuca Ridge, the Mid-Atlantic Ridge, and the Loihi Seamount) and incubated with 13C-labeled bicarbonate. Seafloor-exposed basalts revealed incorporation of 13C-label into organic matter over time, though the degree of incorporation was heterogeneous. The incorporation of 13C into biomass was inconclusive in subseafloor basalts. Translating these measurements into potential rates of carbon fixation indicated that 0.1 – 10 nmol C g-1rock d-1 could be fixed by seafloor-exposed rocks. When scaled to the global production of oceanic crust, this suggests carbon fixation rates of 109 – 1012 g C yr-1, which matches earlier predictions based on thermodynamic calculations. Functional gene analyses indicate that the Calvin cycle is likely the dominant biochemical mechanism for carbon fixation in basalt-hosted biofilms, although the reductive acetyl-CoA pathway and reverse TCA cycle likely play some role in net carbon fixation. These results provide empirical evidence for autotrophy in oceanic crust, suggesting that basalt-hosted autotrophy could be a significant contributor of organic matter in this remote and vast environment.
Fluid mixing and the deep biosphere of a fossil Lost City-type hydrothermal system at the Iberia Margin
Frieder Klein, Susan E. Humphris, Weifu Guo, Florence Schubotz, Esther M. Schwarzenbach, and William D. Orsi*
*C-DEBI Contribution 272
Subseafloor mixing of reduced hydrothermal fluids with seawater is believed to provide the energy and substrates needed to support deep chemolithoautotrophic life in the hydrated oceanic mantle (i.e., serpentinite). However, geosphere-biosphere interactions in serpentinite-hosted subseafloor mixing zones remain poorly constrained. Here we examine fossil microbial communities and fluid mixing processes in the subseafloor of a Cretaceous Lost City-type hydrothermal system at the magma-poor passive Iberia Margin (Ocean Drilling Program Leg 149, Hole 897D). Brucite−calcite mineral assemblages precipitated from mixed fluids ca. 65 m below the Cretaceous paleo-seafloor at temperatures of 31.7 ± 4.3 °C within steep chemical gradients between weathered, carbonate-rich serpentinite breccia and serpentinite. Mixing of oxidized seawater and strongly reducing hydrothermal fluid at moderate temperatures created conditions capable of supporting microbial activity. Dense microbial colonies are fossilized in brucite−calcite veins that are strongly enriched in organic carbon (up to 0.5 wt.% of the total carbon) but depleted in 13C (δ13CTOC = −19.4‰). We detected a combination of bacterial diether lipid biomarkers, archaeol, and archaeal tetraethers analogous to those found in carbonate chimneys at the active Lost City hydrothermal field. The exposure of mantle rocks to seawater during the breakup of Pangaea fueled chemolithoautotrophic microbial communities at the Iberia Margin, possibly before the onset of seafloor spreading. Lost City-type serpentinization systems have been discovered at midocean ridges, in forearc settings of subduction zones, and at continental margins. It appears that, wherever they occur, they can support microbial life, even in deep subseafloor environments.
International Journal of Earth Sciences
Microbial abundance in lacustrine sediments: a case study from Lake Van, Turkey
Jens Kallmeyer, Sina Grewe, Clemens Glombitza, J. Axel Kitte
The ICDP “PaleoVan” drilling campaign at Lake Van, Turkey, provided a long (>100 m) record of lacustrine subsurface sedimentary microbial cell abundance. After the ICDP campaign at Potrok Aike, Argentina, this is only the second time deep lacustrine cell counts have been documented. Two sites were cored and revealed a strikingly similar cell distribution despite differences in organic matter content and microbial activity. Although shifted towards higher values, cell counts from Lake Potrok Aike, Argentina, reveal very similar distribution patterns with depth. The lacustrine cell count data are significantly different from published marine records; the most probable cause is differences in sedimentary organic matter composition with marine sediments containing a higher fraction of labile organic matter. Previous studies showed that microbial activity and abundance increase centimetres to metres around geologic interfaces. The finely laminated Lake Van sediment allowed studying this phenomenon on the microscale. We sampled at the scale of individual laminae, and in some depth intervals, we found large differences in microbial abundance between the different laminae. This small-scale heterogeneity is normally overlooked due to much larger sampling intervals that integrate over several centimetres. However, not all laminated intervals exhibit such large differences in microbial abundance, and some non-laminated horizons show large variability on the millimetre scale as well. The reasons for such contrasting observations remain elusive, but indicate that heterogeneity of microbial abundance in subsurface sediments has not been taken into account sufficiently. These findings have implications not just for microbiological studies but for geochemistry as well, as the large differences in microbial abundance clearly show that there are distinct microhabitats that deviate considerably from the surrounding layers.
Education & Outreach
UNOLS: Chief Scientist Training Cruise
The University-National Oceanographic Laboratory System (UNOLS) of the University of Delaware announces that a Chief Scientist Training Cruise will take place 17-23 November 2015. Focused on robotic and autonomous platforms, this cruise and a pre-cruise information workshop will begin
and end in Lewes, Delaware. The use of robotic and autonomous system aboard UNOLS vessels is
increasing. In addition to traditional shipboard operations, these systems require additional consideration in mission planning, deployment, monitoring, recovery, and communications. Along with providing background on planning shipboard field work, how to request research vessel time, and mechanics of leading a research cruise, the 2015 UNOLS Robotic Platforms Chief Scientist Training Cruise, sponsored by the National Science Foundation and the Office of Naval Research, will focus attention on integration of robotic platforms (i.e. ROV, AUV, UAV) into the training cruise. Small stipends are provided for participant travel costs, research supplies, and shipping. Space is limited. Applicants must be an employee or student (U.S. citizen) at a U.S. institution or a U.S. citizen working abroad. Application deadline: September 14, 2015.
Institute for Broadening Participation (IBP): Minorities Striving and Pursuing Higher Degrees of Success in GEO REU (MS PHD’S–GEO REU) Professional Development Program
Application deadline: September 14, 2015.
The Rolex Scholarships
Application deadline: December 15, 2015.
Simons Foundation: Early Career Investigator in Marine Microbial Ecology and Evolution Awards
The purpose of these awards is to help launch the careers of outstanding investigators who use quantitative approaches to advance our understanding of marine microbial ecology and evolution. Investigators with backgrounds in different fields or with an interest in collaborating with modelers or theorists are encouraged to apply. Investigators may focus directly on marine microbes or on fundamental problems that are highly relevant to understanding marine microbial ecosystems. Among other eligibility requirements, applicants must hold a tenure-track or tenured position (or equivalent) in a U.S. institution, and will have conducted research in such a position for at least two (and no more than eight) years. Applicants may be working in a related field, but must submit an innovative proposal for research that will advance understanding of marine microbial ecology and/or evolution. The deadline for receipt of letters of intent (LOI) is November 2, 2015.
NSF: Scholarships in Science, Technology, Engineering, and Mathematics (S-STEM)
Full proposal deadline: September 22, 2015.
NSF: Graduate Research Fellowship Program (GRFP)
NSF also encourages undergraduate seniors to apply. Application deadline (Geosciences; Life Sciences): October 26, 2015.
National Academies: Research Associateships for Graduate, Postdoctoral and Senior Researchers
There are four annual review cycles and the next closes November 01, 2015.
NSF: Earth Sciences Postdoctoral Fellowships (EAR-PF)
Full proposal deadline: January 12, 2016
NSF: Geobiology and Low-Temperature Geochemistry Program Solicitation
Proposals accepted anytime.
IODP-USSSP: Proposals for Pre-Drilling Activities and Workshops
The U.S. Science Support Program (USSSP) accepts proposals on a rolling basis for pre-drilling activities and semi-annually for workshops, related to the International Ocean Discovery Program (IODP).
Oregon Health & Science University, Institute of Environmental Health: Postdoctoral Position in Environmental & Biomolecular Systems
We seek postdoctoral (Ph.D.) candidates with multidisciplinary training in microbial biochemistry, bioinorganic chemistry, microbiology, (bio)geochemistry, environmental/aquatic chemistry or related fields and expertise with metals. Experience with bacterial culture, protein purification and analytical techniques such as ICP-MS, MIMS, x-ray absorption spectroscopy, electrochemical methods and/or UVVis spectroscopy is desired. As part of the NASA Astrobiology Institute Alternative Earths Research Center at the University of California Riverside, the successful candidate will study the biogeochemistry of enzymatic manganese oxide formation and fractionation of stable isotopes under different environmental conditions. The candidate should have experience and desire to work as part of a multidisciplinary team. The duties include research and publication; training, mentoring, and assisting students, postdocs, staff, etc.; care and maintenance of laboratory equipment and facilities; assisting with project reporting and development; participating in outreach activities; and serving as a liaison with the administration, other faculty and research groups. Some extended travel (including international travel) may be required. The candidate will join a unique, diverse, and highly interdisciplinary department in the Division of Environmental and Biomolecular Systems (EBS), Institute of Environmental Health. This position is located in Portland, Oregon at OHSU’s Marquam Hill Campus. The position is available immediately. Posted July 21, 2015.
Curtin University, Perth: PhD scholarships
Several PhD scholarships are available for national and international students (including fee waivers for exceptional scholars). Priority areas: Application of biomarkers (organic geochemistry), compound-specific isotope analysis, palaeogenomics and geomicrobiology. Please send Expression of interest, CV and names of three referees to: Professor Kliti Grice, K.Grice@curtin.edu.au and A/Professor Marco Coolen, Marco.Coolen@curtin.edu.au.
IODP/Texas A&M: Assistant Research Scientist – Expedition Project Manager/Staff Scientist – Borehole Geophysics
We will begin reviewing applications on September 15, 2015, but will continue to accept applications until candidates are selected for interviews.
All required application materials submitted by September 15, 2015 are ensured full consideration.
Ecole Polytechnique Federale Lausanne (EPFL) / Environmental Microbiology Laboratory (EML): Postdoctoral researcher position to investigate the microbial community in deep sulfidic boreholes in Finland
Start date: October 01, 2015.
Rice University: Wiess Post-Doctoral Research Fellowship in Earth and Planetary Science
The application deadline is November 1, 2015.
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