Planktonic Archaeal Phosphorus Affinity and Apportionment (PAPAA)

• Applicant: Dr. Travis Meador
• Subject Area: Oceanography
• Term: from 2015 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 290341800

This project will investigate the pathways and fluxes of nutrient recycling in oceanic surface waters by quantifying the phosphate affinity as well as the release of organic phosphonates and phosphate esters by a model organism, Nitrosopumilus maritimus, a prolific planktonic archaeon. This organism plays a crucial role in the global nitrogen cycle, specializing in the conversion of recycled nitrogen (i.e., ammonia) to inorganic nitrite in order to generate energy, and in the global carbon cycle, assimilating inorganic carbon into biomass. Given the small biovolume of the cell, high phosphate uptake affinity and uptake capacity in combination with access to the dissolved organic phosphorous (DOP) pool may offer N. maritimus a competitive advantage in regions of the ocean subject to P limitation. The proposed study will assess the role of N. maritimus in the marine phosphorus cycle by quantifying the uptake and partitioning of P and by employing novel isolation and chemical characterization techniques to identify individual P-containing macromolecules. Specifically, I will optimize an existing method that capitalizes on the binding of P by an iron oxide resin to isolate DOP from seawater media, followed by subsequent structural elucidation and compound-specific quantification via tandem liquid chromatography mass spectrometry. The proposed DOP characterization method will allow, for the first time, identification of the macromolecular forms of organically-bound P and associated fluxes of these compounds. This information is essential for assessing DOP biosynthetic pathways and bioavailability, representing a caveat that has plagued previous microbiological and geochemical assessments of the spatial distribution and turnover of DOP in aquatic environments. In addition to these primary goals, combined results from this study will also provide estimates of cellular budgets and fluxes of carbon, nitrogen, and phosphorus in N. maritimus, which may occupy a distinct niche in the marine P cycle.

• DFG Programme: Research Grants