Astrobiology research in J. Hayes' lab continues to focus on novel applications of isotopic biogeochemistry. Research on the C-isotopic measurement of SSU ribosomal RNA genes has borne its initial fruit, providing a technique that can provide both phylogenetic and physiological information on organisms present in natural ecosystems. Collaboration in measuring bacterial fractionations of hydrogen isotopes (with L. Jahnke of the NASA/Ames Astrobiology team) led to an extensive paper describing the sources of H used in biosynthesis of lipids by the aerobic methanotroph, Methylococcus capsulatus, and the isotopic fractionations associated with its biosynthetic pathways. In collaboration with new team member Roger Summons, Hayes' lab has completed H-isotopic analyses of an extensive series of oils from Australia. The results suggest that hydrogen isotopic compositions of sedimentary hydrocarbons are minimally affected by diagenetic processes and so can be used to resolve mixtures of sedimentary compounds with distinct biological sources.
Our newest team member, Roger Summons, conducts research on the chemical and isotopic characterization and biogeochemical significance of lipids from cultured microbes, environmental samples and their fossil analogues in ancient sedimentary environments. In collaboration with L. Jahnke (NASA Ames) and others, Summons is currently analyzing the lipids of a number of new isolates of thermophilic and hyperthermophilic bacteria, greatly extending our understanding of the variety and complexity of extremophile lipid biosignatures. Preliminary research has begun on organic-rich, low maturity sediments that span both the Precambrian-Cambrian (Oman) and Permo-Triassic (Australia) boundaries, with the goal of detecting molecular biomarkers that might be diagnostic for biogeochemical processes.