Project: Marine biopolymers as tracers of major biogeochemical processes: Using proteomics and antibody-sensor technology

Description from NSF award abstract:
Recent advances in proteomics, biomarkers and biosensor technology sciences enable new approaches to understanding major biogeochemical processes. This project will examine the physicochemical reactivity of a model protein "RuBisCO" in seawater, and will quantify RuBisCO along ocean transect Line P (48 39.0N, 126 40.0 W to 50 00N, 145 00W) in the North Pacific Ocean. The project will use two independent methods that complement and validate each other: immune-sensors and multiple-reaction monitoring (MRM) mass spectrometry.

Chemical analyses have shown that a significant fraction of dissolved organic matter (DOM) in the ocean is in the form of proteins. Proteins are a rich source of biological information and their amino acid sequence provides a direct link to the coding DNA of an organism. Identification of proteins in DOM opens a window to understanding the complex sources and dynamics of biopolymeric material. Furthermore, proteins represent the catalytic potential and reactivity of an organism and, collectively, of an ecosystem. Most importantly, the information also provides a direct link between biological and phylogenetic presence and biogeochemistry. The distributions of proteins that are specific to major processes (e.g., RuBisCO to carbon fixation, nitrogenase to diazotrophy) can be used to infer information that has been hidden until now.

The PIs have recently demonstrated the deep distribution of RubisCO in the North Pacific and discovered this enzyme to be at high concentrations throughout the water column (to depths >3000 m) underlying highly productive equatorial and subpolar systems, and low concentrations under the oligotrophic subtropical gyre. This single protein represents ~2% of the largely unidentified dissolved organic nitrogen pool at depths >1000 m. The deep distribution of RuBisCO shows that hydrographic fronts in the surface ocean affect the distribution of recently-produced organic matter thousands of meters below the ocean surface, and the enzyme traces the transport of deep organic matter by the deep ocean circulation away from regions of input. These findings suggest that the identification and quantification of additional biomarker proteins will provide a powerful approach to understanding the associated biogeochemical pathways. While potentially transformative, the protocols need to be explored and validated.

In this study, the PIs will compare and validate their previous findings by understanding the physicochemical reactivity of RuBisCO (and therefore other proteins) in seawater samples in order to fully interpret and exploit the information held in protein distributions; and they will quantify RuBisCO at Line P in fresh samples using two independent and different methods that complement and validate each other: immunosensors and multiple-reaction monitoring (MRM) mass spectrometry in a coastal to open ocean transect.