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Project Progress

Fogel and Ziegler established the isotopic biosignatures of bacteria and how these organisms transform primary, in this case photosynthetic, isotopic and protein signals into altered microbial biosignatures. We found that bacteria totally resynthesized and scrambled the isotopic patterns in amino acids. The process was rapid for soluble proteins, e.g. Rubisco. Bacteria proteins were mineralized and recycled as well. Our data shows that on very short time scales, hours to days to months, microbial products are formed and degraded. The biologically-resistant material gradually obtains an isotopic and chemical composition that has little resemblance to original biochemical compounds. Bacteria from the Archae and the Eubacteria were cultured at the Geophysical Laboratory by James Scott or at the American Type Culture Collection in collaboration with David Emerson. The work is continuing on several fronts: James Scott is actively seeking to determine the carbon isotope fractionation during acetogenesis. He has examined cultures of acetogens that have been grown heterotrophically and found that the cellular carbon is derived from components in the medium without major isotopic fractionation. Autotrophic cultures are being grown presently. More individual amino acid isotopic analyses are planned for the cultured microorganisms. We used SELDI technology to determine the nature of high molecular weight organic molecules found in oceanic and aquatic dissolved organic matter DOM to see whether we could detect large proteins or peptidoglycan fragments. The results of these experiments are as follows:
The molecular weight distribution of the samples was in the range of 800 to 6,000 daltons. No material was detected between 10,000 and 100,000 daltons. â?? A set of fourteen peaks was found in both the riverine and oceanic DOM (Figure 1).
â?? The riverine sample had the highest molecular weight peak at 6,000 daltons. This broad peak indicated a glycoprotein or other carbohydrate-bound moiety.
â?? The oceanic DOM sample had a series of molecular fragments in the range of 1,200 to 2,300 that were unique to this sample.
â?? Both samples had a suite of peaks that corresponded to a class of compounds with subunits in the range of 200-230 daltons.