Project: Collaborative Research: Assessing the role of compound-specific phosphorus hydrolase transformations in the marine phosphorus cycle

Acronym/Short Name:P-hydrolase
Project Duration:2017-09 - 2022-08

Description

NSF Award Abstract:
Phosphorus (P) is an essential building block for life. Because P is in short supply over vast areas of the ocean, P availability may control biological productivity, such as photosynthesis and carbon fixation, which has implications for uptake of the greenhouse gas carbon dioxide and thus climate regulation. Marine microorganisms must satisfy their nutritional requirement for P by obtaining it from seawater, where P is present in a variety of chemical forms, from simple phosphate ions (Pi) to complex dissolved organic phosphorus (DOP) molecules. The concentration of DOP vastly exceeds Pi over most ocean areas, therefore DOP is a critically important source of P for marine microbial nutrition and productivity. However, much remains unknown about the contribution of specific DOP compounds to the P nutrition, productivity, and structure of marine microbial communities. In this project, the investigators will conduct field experiments in the Atlantic Ocean and perform a series of controlled laboratory studies with pure enzymes and microbial cultures to determine how and to what extent different DOP compounds are degraded to Pi in the marine environment. Furthermore, the contribution of these compound-specific DOP molecules to microbial P nutrition, carbon fixation, and community structure will be determined, thus advancing the current state of knowledge regarding the factors that control the activity and distribution of microbial species in the ocean, and the ocean?s role in the climate system. This project will support two female junior investigators, a postdoctoral researcher, and graduate and undergraduate students. The undergraduate students will be recruited from the Marine Sciences program at Savannah State University, an Historically Black Colleges and Universities. In addition, results will be incorporated into new hands-on K-12 educational tools to teach students about microbial P biogeochemistry, including a digital game and formal lesson plans with hands-on demos. These tools will be validated with K-12 educators and will be widely accessible to the public through various well-known online platforms. These activities will thus reach a broad audience including a significant fraction of underrepresented groups.

P is a vital nutrient for life. Marine microorganisms utilize P-hydrolases, such as alkaline phosphatase (AP), to release and acquire phosphate (Pi) from a wide diversity of dissolved organic P (DOP) compounds, including P-esters (P-O-C bonds), phosphonates (P-C), and polyphosphates (P-O-P). Compound-specific DOP transformations have the potential to exert critical and wide-ranging impacts on marine microbial ecology (e.g. variable DOP bioavailability among species), biogeochemistry (e.g. P geologic sequestration via formation of calcium Pi), and global climate (e.g. aerobic production of the greenhouse gas methane by dephosphorylation of methylphosphonate). However, the mechanisms and comparative magnitude of specific DOP transformations, in addition to their relative contributions to microbial community-level P demand, productivity, and structure, are not completely understood. This study will fill these knowledge gaps by tracking the fate of specific DOP pools in the marine environment. Specifically, this project will test four hypotheses in the laboratory using recombinant enzymes and axenic cultures representative of marine eukaryotic and prokaryotic plankton from high and low nutrient environments, and in the field using observational and experimental approaches along natural Pi gradients in the Atlantic Ocean. In particular, the investigators will reveal potential differences in the hydrolysis and utilization of specific DOP compounds at the community- (bulk enzymatic assays), taxon- (cell sorting of radiolabeled cells in natural samples), species- (axenic cultures) and molecular-levels (pure enzyme kinetic studies and cell-associated proteomes and exoproteomes). Results from our proposed work will provide a robust understanding of the enzymatic basis involved in the transformation of specific forms of DOP and create new knowledge on the relative contribution of these specific P sources to Pi production, marine microbial nutrition, community structure, primary productivity, and thus global carbon cycling and climate. In particular, our refined measurements of the concentration of bioavailable DOP and our unique estimates of DOP remineralization fluxes will provide critical new information to improve models of marine primary production and P cycling.


DatasetLatest Version DateCurrent State
In vivo fluorescence and flow cytometry cell counts from dissolved organic phosphorus (DOP) hydrolysis experiments with marine cyanobacterium Synechococcus laboratory cultures (WH8102 and WH5701) from 2018-20232024-06-06Final no updates expected
Laboratory-cultured Synechococcus (WH8102 and WH5701) MUF-P hydrolysis inhibition by dissolved organic phosphorus (DOP) from experiments between 2018-20232024-06-06Final no updates expected
Laboratory-cultured Synechococcus (WH8102 and WH5701) growth (vivo fluorescence) on dissolved organic phosphorus (DOP) from experiments between 2018-20232024-06-03Final no updates expected
Hydrolysis rates from dissolved organic phosphorus (DOP) hydrolysis experiments with marine cyanobacterium Synechococcus laboratory cultures (WH8102 and WH5701) from 2018-20232024-05-28Final no updates expected
Dissolved organic phosphorus (DOP) hydrolysis rates from Ruegeria pomeroyi laboratory cultures2023-06-09Final no updates expected
Optical density and cell counts from flow cytometry of Ruegeria pomeroyi laboratory cultures2023-06-09Final no updates expected
Concentrations of particulate phosphate in seawater collected during R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in the Spring of 20192021-11-02Data not available
Phytoplankton and heterotrophic bacterial cell abundance over the incubation period ​in bioassay experiments with seawater from R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in Spring of 20192021-11-02Data not available
Alkaline phosphatase activity over bioassay experiments with seawater from R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in Spring of 20192021-11-02Data not available
Phytoplankton and heterotrophic bacterial cell abundance in seawater collected during R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in the Spring of 20192021-11-02Data not available
Concentrations of particulate phosphate in treatments amended with dissolved organic phosphate compounds in bioassay experiments (incubation 48h) with seawater from R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in Spring of 2019 2021-11-02Data not available
Alkaline phosphatase activity (APA) Michaelis-Menten kinetic parameters (Vmax and Km) in both whole and filtered seawater collected during R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in the Spring of 20192021-11-02Data not available
Concentrations of soluble reactive phosphate in treatments amended with dissolved organic phosphate compounds in bioassay experiments (incubation 48h) with seawater from R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in Spring of 2019 2021-11-02Data not available
Bioavailability factor of polyphosphate, nucleotides (ATP and AMP) and phosphonate in seawater collected during R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in the Spring of 20192021-11-02Data not available
Bioavailability factor of polyphosphate, nucleotides, and methyl phosphonate in bioassay experiments with seawater from R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in Spring of 2019 2021-11-02Data not available
Turnover time and uptake rates of phosphate in treatments amended with dissolved inorganic and organic phosphate compounds in bioassay experiments (incubation 48h) with seawater from R/V Savannah cruise SAV-19-02 in the NW Atlantic Ocean in Spring 2019 2021-11-02Data not available

People

Lead Principal Investigator: Julia Diaz
University of Georgia (UGA)

Principal Investigator: Solange Duhamel
Lamont-Doherty Earth Observatory (LDEO)

Contact: Julia Diaz
University of Georgia (UGA)


Data Management Plan

DMP_Diaz_Duhamel_OCE-1736967_1737083.pdf (71.13 KB)
02/09/2025