Linking microbial metabolism and organic matter cycling through metabolite distributions in the ocean

Key players in the marine carbon cycle are the ocean-dwelling microbes that fix, remineralize, and transform organic matter. Many of the small organic molecules in the marine carbon pool have not been well characterized and their roles in microbial physiology, ecological interactions, and carbon cycling remain largely unknown. In this dissertation metabolomics techniques were developed and used to profile and quantify a suite of metabolites in the field and in laboratory experiments. Experiments were run to study the way a specific metabolite can influence microbial metabolite output and potentially processing of organic matter. Specifically, the metabolic response of the heterotrophic marine bacterium, Ruegeria pomeroyi, to the algal metabolite dimethylsulfoniopropionate (DMSP) was analyzed using targeted and untargeted metabolomics. The manner in which DMSP causes R. pomeroyi to modify its biochemical pathways suggests anticipation by R. pomeroyi of phytoplankton-derived nutrients and higher microbial density. Targeted metabolomics was used to characterize the latitudinal and vertical distributions of particulate and dissolved metabolites in samples gathered along a transect in the Western Atlantic Ocean. The assembled dataset indicates that, while many metabolite distributions co-vary with biomass abundance, other metabolites show distributions that suggest abiotic, species specific, or metabolic controls on their variability. On sinking particles in the South Atlantic portion of the transect, metabolites possibly derived from degradation of organic matter increase and phytoplankton-derived metabolites decrease. This work highlights the role DMSP plays in the metabolic response of a bacterium to the environment and reveals unexpected ways metabolite abundances vary between ocean regions and are transformed on sinking particles. Further metabolomics studies of the global distributions and interactions of marine biomolecules promise to provide new insights into microbial processes and metabolite cycling.

Department dc:contributor.department

Joint Program in Oceanography/Applied Ocean Science and Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2017

Author dc:creator

• Johnson, Winifred M., Ph. D. Massachusetts Institute of Technology

Advisor dc:contributor.advisor

• Elizabeth B. Kujawinski.

• Joint Program in Oceanography/Applied Ocean Science and Engineering.
• Earth, Atmospheric, and Planetary Sciences.
• Woods Hole Oceanographic Institution.

Statement dc:rights

• MIT theses are protected by copyright. They may be viewed, downloaded, or printed from this source but further reproduction or distribution in any format is prohibited without written permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/108909

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/108909