In my 1979 application to be a staff member of the Geophysical Laboratory, I wrote “Geochemists base much of their interpretations of sedimentary carbon on the premise that bacteria have little to do with changing or fractionating isotopes in sediments.” I proposed to examine the isotope fractionations in lipids from cultures of microbes, to isolate microbes from various environments, and to incubate samples in situ and follow changes in their chemistry and isotopic compositions. My early work in this area started with the microbes at Yellowstone National Park (see above; Estep, 1984 and Estep and Macko, 1984). Investigations with...

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