| Summary: | The response of global carbon and nitrogen cycles to future climate change is uncertain. In order to understand the impacts that future changes to climate will have on these cycles, a more detailed understanding of them is essential. This dissertation utilizes a combined approach of molecular biomarkers and proteomic investigations to elucidate historic source material contributions and microbial protein production to contribute to a more thorough understanding of the marine carbon and nitrogen cycles. The examination of molecular organic biomarkers throughout an Arctic sediment core showed the dominant input in the area was from marine sources with lower but steady contributions from terrestrial sources during the Holocene. Attempts to recover proteins from deeper sediments to correlate with lipid biomarkers were unsuccessful but led to the optimization of an extraction protocol for an added protein standard, bovine serum albumin, from sediments. An investigation into the expressed proteome of the heterotrophic marine bacterium, Ruegeria pomeroyi , under environmentally realistic carbon supply conditions during exponential and stationary growth phases identified over 2000 proteins. The most abundant proteins identified were responsible for porins, transport, binding, translation, and protein refolding and could represent potential biomarkers of bacterial processes and/or activity. A parallel study of R. pomeroyi , in which 13 C-labeled leucine was added to the culture during exponential growth phase, showed labeled incorporation ranging from 16 to 21% of the total proteins produced depending on growth phase. The widespread distribution of the label among the growth phases indicates active recycling by the bacteria. This study demonstrates a method through which bacterial protein synthesis can be tracked. A study of the marine diatom Thalassiosira pseudonana acclimated to iron replete or iron-limited conditions showed iron-limited organisms increased proteins involved in pathways associated with intracellular ...
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