LExEn: Integrated Biogeochemical and Microbiological Studies of Cold, Anoxic Environments

University Of California-Irvine, Irvine CA

Investigators

Abstract

LExEn: Integrated Biogeochemical and Microbiological Studies of Cold, Anoxic Environments Although cold, anoxic marine sediments are a seemingly inhospitable location to support life, they are populated by microbes with unusual metabolic capabilities. They play a key role in the global cycling of organic matter today and in the past, and are also important for our understanding of life elsewhere in the Universe. Although previous studies have considered such environments, numerous questions still remain about the microbial communities and processes which occur there. The objectives of the current project are to further the understanding of the processes occurring in cold, anoxic systems, and to link the understanding of the processes with the microbial communities that participate. More specifically, this project will couple biogeochemical experiments performed at a permanently-cold, anoxic bay with sophisticated chemical analyses, culture-dependent and independent identification techniques, and laboratory-based studies of microbes isolated from the site, to provide a more comprehensive understanding of the microbiology and biogeochemistry of such globally-important environments. Specific Goals Include: 1. Determine the prokaryotic community structure of the study site (sediments of Skan Bay, AK). Several independent techniques will be utilized encompassing both culture-dependent (most-probable- number analysis, isolations) and culture-independent (complete depth-profile using 16SrRNA, DGGE, species-specific fluorescent probes, lipid biomarker analysis) identification techniques. 2. Determine the pathways and thermodynamics of carbon and energy flow at the site. Several independent approaches will be utilized including following natural isotopic variations (lipid biomarker isotope analysis - 2 H and 13 C, methane isotope analysis - 2 H and 13 C), utilizing isotope-labeled tracers (14 C-labeled methane, acetate, glucose), and determining depth profiles of important metabolites (CH4, SO4 2- , and H2). 3. Isolate and characterize novel psychrophilic and psychrotolerant prokaryotes, including methanogens, sulfate reducing bacteria, amino-acid degrading syntrophs, and methane oxidizers. 4. Integrate all laboratory and field studies with prior studies to develop a conceptual model of the microbial-biogeochemistry of cold, anoxic environments. This project will also yield insight into the formation and consumption of methane hydrates by microbes. This work should also lead to the isolation and characterization of several novel prokaryotes capable of growth at low temperature, including sulfate-reducing bacteria, methanogenic Archaea, methane-oxidizing Archaea, and amino-acid consuming syntrophs. In addition, this work will help to identify the mechanism and organisms responsible for anaerobic methane oxidation. Results of this work are expected to be broadly applicable to other extreme environments.