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dc.contributor.advisorMichael J. Follows.en_US
dc.contributor.authorRao, Deepa,Ph.D.Massachusetts Institute of Technology.en_US
dc.contributor.otherJoint Program in Oceanography/Applied Ocean Science and Engineering.en_US
dc.contributor.otherMassachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciences.en_US
dc.contributor.otherWoods Hole Oceanographic Institution.en_US
dc.date.accessioned2020-10-08T21:29:52Z
dc.date.available2020-10-08T21:29:52Z
dc.date.copyright2020en_US
dc.date.issued2020en_US
dc.identifier.urihttps://hdl.handle.net/1721.1/127908
dc.descriptionThesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), May, 2020en_US
dc.descriptionCataloged from the official PDF of thesis.en_US
dc.descriptionIncludes bibliographical references (pages 161-183).en_US
dc.description.abstractHighly productive marine microbial communities in the coastal Southern Ocean sustain the broader Antarctic ecosystem and play a key role in Earth's climate via the biological pump. Regional phytoplankton growth is primarily limited by iron and co-limited by cobalamin (vitamin B₁₂), a trace cobalt-containing organometallic compound only synthesized by some bacteria and archaea. These micronutrients impact primary production and the microbial ecology of the two keystone phytoplankton types: diatoms and Phaeocystis antarctica. This thesis investigates microbe-driven cobalamin cycling in Antarctic seas across multiple spatiotemporal scales. I conducted laboratory culture experiments with complementary proteomics and transcriptomics to investigate the B₁₂-ecophysiology of P. antarctica strain CCMP 1871 morphotypes under iron-B₁₂ co-limitation.en_US
dc.description.abstractWe observed colony formation under higher iron treatments, and a facultative use of B₁₂-dependent (MetH) and B₁₂-independent (MetE) methionine synthase isoforms in response to vitamin availability, demonstrating that this strain is not B₁₂-auxotrophic. Through comparative 'omics, we identified a putative MetE protein in P. antarctica abundant under low B₁₂, which is also found in other marine microbes. Across Antarctic seas, community-scale cobalt and B₁₂ uptake rates were measured by ⁵⁷Co radiotracer incubation experiments and integrated with hydrographic and phytoplankton pigment data. I observed significant correlations between uptake fluxes and environmental variables, providing evidence for predominantly diatom-driven uptake of these micronutrients in warmer, fresher surface waters with notable regional differences.en_US
dc.description.abstractTo date, this work is the most comprehensive attempt to elucidate the processes governing the co-cycling of cobalt and B₁₂ in any marine system. At the ecosystem-scale, I developed and tested a hypothesis of micronutrient-driven community dynamics through a trait-based model with cross-feeding interactions. The model demonstrates how the observed seasonal succession of springtime P. antarctica from solitary to colonial cells, bacterioplankton, and summertime diatoms may be explained by the microbial cycling of iron, dissolved organic carbon, and B₁₂. Overall, this dissertation provides new information about the micronutrient-driven ecology of Antarctic marine microbes and adds to our understanding of the interconnections between organismal life cycle, trace metals, and trace organics in marine environments.en_US
dc.description.statementofresponsibilityby Deepa Rao.en_US
dc.format.extent183 pagesen_US
dc.language.isoengen_US
dc.publisherMassachusetts Institute of Technologyen_US
dc.rightsMIT theses may be protected by copyright. Please reuse MIT thesis content according to the MIT Libraries Permissions Policy, which is available through the URL provided.en_US
dc.rights.urihttp://dspace.mit.edu/handle/1721.1/7582en_US
dc.subjectJoint Program in Oceanography/Applied Ocean Science and Engineering.en_US
dc.subjectEarth, Atmospheric, and Planetary Sciences.en_US
dc.subjectWoods Hole Oceanographic Institution.en_US
dc.titleCharacterizing cobalamin cycling by Antarctic marine microbes across multiple scalesen_US
dc.typeThesisen_US
dc.description.degreePh. D.en_US
dc.contributor.departmentJoint Program in Oceanography/Applied Ocean Science and Engineeringen_US
dc.contributor.departmentMassachusetts Institute of Technology. Department of Earth, Atmospheric, and Planetary Sciencesen_US
dc.contributor.departmentWoods Hole Oceanographic Institutionen_US
dc.identifier.oclc1197629828en_US
dc.description.collectionPh.D. Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution)en_US
dspace.imported2020-10-08T21:29:51Zen_US
mit.thesis.degreeDoctoralen_US
mit.thesis.departmentEAPSen_US


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