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Project Progress

For geochemical processes and biosignatures, Aubrey Zerkle made great progress in understanding trace metal limitation during nitrogen-fixation by cyanobacteria. This work has disproven the hypothesis by Anbar and Knoll (2002) that the Proterozoic ocean was limited by Mo, as well as discovered a novel negative _15N isotope signature for increased Fe-availability in the rock record. Also, Vyllinniskii Cameron made important efforts in understanding trace metal content and acquisition by hydrothermal microorganisms. The work has shown that these species probably do not release metal-binding ligands.

Undergraduate Chris Urban has shown that Barite is actively dissolved by sulfate-reducing bacteria, which may be an important sink for methane in deep sea sediments. Undergraduate student Jenny Vrentas has found that different vitamins act as controls on isotopic fractionation during methanogenesis. We are also moving forward with studies of microbial microcosms as models for the oceans through time, and efforts are currently geared towards understanding the transition from anoxygenic photosynthetic communities to oxygenic photosynthetic communities on early Earth.

In our efforts to link geochemistry with phylogenetics, Jen Biddle has made insights in the microbiology of deeply buried marine sediments in areas of anaerobic methane oxidation using FISH-SIMS and culturing techniques. Jim Moran has made further progress with efforts to develop a method for the capture and isotopic analysis of rRNA. Aubrey Zerkle has investigated the coevolution of microbial metal use and carbon isotope signatures with changing environmental conditions through time.

I have also made some progress redefining the Tree of Life by developing a method for building Prokaryotic trees based entirely on Gene Order. Additionally, we have created consensus phylogenetic trees based on the combined gene content of groups of individual prokaryotes.