Each year microbes in the ocean convert about half of the 50-90 billion tons of
carbon from carbon dioxide, a greenhouse gas, into a dissolved organic form. Much of this dissolved organic matter (DOM) is stored for months, or even years, in the upper waters of the ocean before being turned back into carbon dioxide. In waters that are very low in other nutrients necessary to support life in the oceans, this “semi-labile” DOM is an important source of nutrients and energy. In this project, we’re investigating why some organic matter lasts as long as it does in the oceans and how microbes use this material to sustain themselves.
Our project is designed to isolate, cultivate and characterize microbes that drive
semi-labile DOM cycling, and to develop model systems to explore the physiology, ecology and biogeochemistry of DOM turnover in nutrient-poor waters. Another major goal is to define aspects of the chemical make-up of semi-labile DOM. Major components of DOM will be purified and characterized, then used as substrates in high throughput culture screens. This project is primarily focused on the polysaccharide fraction of semi-labile DOM. We will use chromatography to separate and purify major DOM polysaccharides that will be characterized by mass spectrometry and nuclear magnetic resonance spectroscopy. We will also characterize the genomes and transcriptomes of the DOM-degrading bacterial isolates, to identify the major metabolic pathways involved in its degradation and oxidation. Our approach will leverage the microbiology to elucidate details of DOM-degradation biochemistry, and conversely will use DOM chemical characterization and manipulation, to test hypotheses about the microbial oxidation and turnover of DOM.
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