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Project Progress

Molecular and Isotopic Approaches to Microbial Ecology and Biogeochemistry (dm)

The Harvard team has been working to develop techniques for the analysis of 13C in sub-nanomole quantities of nucleic acids. Thus far, we have demonstrated accurate analyses of sub-nanomole quantities of carbon in samples of nucleic acids and have gained experience with the isolation of native RNA from laboratory cultures and natural samples. Our goal is to use probe-capture techniques for the isolation of specific nucleic acids. At present, we can obtain high purity (i. e., capture of RNA from only a single species) or reasonable yield, but not both at the same time. We are continuing to pursue techniques with high genomic resolution and expect eventual success.

We have collaborated with NASA Ames in studies of the fractionation of hydrogen isotopes by methanotrophic bacteria. These organisms provide an ideal entry point to the study of unicellular systems because H can flow from only two possible sources, the C-H bonds of methane or the O-H bonds of water. Interactions with the Ames group also led to the identification of a series of cultures of sulfate-reducing bacteria. We have completed hydrogen-isotopic analyses of the lipids from these same samples. We have also worked with members of the Ames group in investigations of carbon-isotopic biogeochemical studies of hydrothermal vent microbial communities. Hayes has completed a major review entitled “Fractionation of the isotopes of carbon and hydrogen in biosynthetic processes.”

We are beginning to investigate how methane functioned in Earth’s early atmosphere, using detailed studies of how methanogenesis occurs in modern sediments, and working to calculate the rates of microbial reactions. We are also developing the ability to measure calcium isotopes with high precision to investigate biomineralization in Proterozoic sediments.