Biogeochemistry of Isoprenoid Production and Anaerobic Hydrocarbon Biodgeradation

Open Access
Dawson, Katherine Strigari
Graduate Program:
Doctor of Philosophy
Document Type:
Date of Defense:
April 11, 2011
Committee Members:
  • Jennifer Macalady, Dissertation Advisor
  • Jennifer Macalady, Committee Chair
  • Katherine Haines Freeman, Committee Chair
  • Christopher Howard House, Committee Member
  • John Michael Regan, Committee Member
  • archaeal lipids
  • halophilic archaea
  • coal bed methane
  • hydrocarbon biodegradation
  • anaerobic
  • isoprenoids
This dissertation is an exploration of microbial isoprenoid production and destruction by anaerobic hydrocarbon biodegradation. Isoprenoids are methyl-branched hydrocarbons, and include biomarkers from all three domains of life such as archaeal lipids, hopanoids, and sterols. Isoprenoid production was examined through variation in the molecular structure of archaeal lipids across a hypersaline gradient (Chapter 5). This study identified unsaturated analogues of archaeol in four halophilic archaeal strains and revealed an increase in the percentage of unsaturated lipids with increasing salinity. Anaerobic isoprenoid biodegradation was examined through the enrichment of bacteria under anaerobic conditions utilizing pristane as a carbon source (Chapter 2). Further analysis of anaerobic degradation utilized 13C-labelled phytane as a stable isotope tracer (Chapter 3). In both cases, a microbial community dominated by denitrifying Beta- and Gammaproteobacteria was responsible for the degradation of pristane and phytane. Environmental anaerobic hydrocarbon degradation was examined through the analysis of in situ microbial communities associated with the transformation of coal to methane (Chapter 4). Through FISH and 16S rRNA tag pyrosequencing a coal transformation pathway ending in acetoclastic/methylotrophic methanogenesis was identified in the Cook Inlet Basin, Alaska. These studies demonstrate the microbial impact on hydrocarbon production and alteration, which influences the transition over geologic time scales from biomolecules to biomarkers in the sedimentary record.