Award: OCE-1031271

During this project, we have explored the fundamental biochemistry of marine microbial organisms and the way in which those microbial communities can affect the chemistry of the ocean. Specifically, we focused on proteins, a class of compounds that are responsible for catalyzing the fundamental biochemical reactions inside cells. We have, for the first time, generated vertical profiles of the concentrations of a number of important proteins in the ocean and these profiles have revealed previously unseen details regarding how the ocean operates. Many of the proteins that we are particularly interested in require a metal atom to be part of their structure (metalloproteins or metalloenzymes). Such metalloproteins are often found as part of a reaction sequence involving oxidation/reduction reactions and are therefore fundamental to the generation and transformation of energy. For example, photosynthesis and nitrate reduction, two processes that are important in our study area of the tropical Pacific Ocean, require metals (iron, manganese and copper). In some instances, organisms find it difficult to obtain enough of these metals to satisfy their metabolic needs, resulting in growth or activity limitation. The tropical Pacific is an example of a location where photosynthesis is iron-limited. Our proteomic results were able to detect which regions were limited by nitrogen, iron and phosphorus using biomarkers, which are molecule that are diagnostic of microbial cellular metabolism. Wealso examined the metal requirements of aerobic heterotrophic organisms (ones that degrading existing organic matter for energy), particularly for zinc. This is because several important classes of proteins involved in degradation, notably proteases and phosphatases, require zinc to function properly at the pH of seawater. We observed a stimulatory response of zinc on the activity of phosphatases in sediment trap experiments, which implies there could be zinc limitation of these microbial remineralization processes and has implications for carbon cycling in the oceans. Finally, we also hypothesized that metal limitation of protein function might affect the behavior of the toxic element mercury in the ocean. We found evidence that the transformation of mercury into the form that bioaccumulates in fish is connected to the activity of group of proteins that are related to vitamin B12, a cobalt containing biomolecule. A connection to proteins that use B12 has been observed in laboratory studies, but this is the first time that field data have suggested a similar connection. Thus, our research on this project has developed novel biochemical methods to study the oceans and has provided fundamental information on the healthy function of the ocean, as well as processes that could if disturbed, represent a threat to the health of people. Last Modified: 12/29/2013 Submitted by: Carl H Lamborg