Ingalls, Anitra EHeal, Katherine2018-07-312018-07-312018Heal_washington_0250E_18390.pdfhttp://hdl.handle.net/1773/42503Thesis (Ph.D.)--University of Washington, 2018Organic molecules play a myriad of roles in the surface ocean. They are the building blocks of proteins, the alphabet of genetic information, and the language in which microorganisms communicate. The small biomolecules that are the readout of cellular activity, or metabolites, or are of particular interest. Some metabolites like compatible solutes fuel the microbial loop, while others like vitamins act as micronutrients to algae. In this dissertation, I aim to use liquid-chromatography mass-spectrometry (LC-MS) to observe pools of metabolites to answer long-standing questions in microbial ecology and organic matter cycling in the surface ocean, specifically tackling gaps in our knowledge regarding cobalamin (vitamin B12) and microbial metabolomics. In Chapters 2 and 3, I develop and utilize LC-MS techniques to directly measure cobalamin in dissolved and particulate organic matter. These chapters reveal an underappreciated chemical diversity of cobalamin and cobalamin-like compounds in marine systems, revealing that cyanobacteria produce a cobalamin-like compound, pseudocobalamin. I tie this chemical diversity to the biochemistry, ecology, and evolution of marine cobalamin producers in Chapter 3. In Chapters 4 and 5, I use an analytical technique to perform targeted and untargeted metabolomics. These techniques aim to identify and quantify the entire metabolome of an organism (as in Chapter 4) or community (as in Chapter 5). In a controlled laboratory setting, I harness metabolomics to understand how two species of diatoms experience cobalamin limitation; this work is presented in Chapter 4. In Chapter 5, I explore the whole community metabolome across a natural oceanographic gradient in temperature, salinity, and nutrients in the North Pacific Ocean. Here I offer some of the first observations of several metabolites in natural marine systems and hypothesize on their roles in microbial processing of organic matter.application/pdfen-USnoneCobalaminMarineMetabolomicsChemical oceanographyBiological oceanographyBiogeochemistryOceanographyThesis