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Unraveling the Unseen Players in the Ocean - A Field Guide to Water Chemistry and Marine Microbiology
Published on: November 5, 2014
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Cryptic carbon and sulfur cycling between surface ocean plankton
Bryndan P Durham1, Shalabh Sharma2, Haiwei Luo2
1Department of Microbiology, University of Georgia, Athens, GA 30602;
Summary
Marine bacteria metabolize half of ocean carbon via dissolved organic carbon (DOC). Researchers identified 2,3-dihydroxypropane-1-sulfonate (DHPS) as a key metabolite exchanged between diatoms and bacteria, impacting carbon and sulfur cycles.
Area of Science:
- Marine microbial ecology
- Biogeochemical cycles
- Phytoplankton-bacteria interactions
Background:
- Marine bacteria consume roughly half of carbon fixed by phytoplankton, mediated by dissolved organic carbon (DOC).
- The chemical complexity of marine DOC and limited knowledge of trophic interactions hinder understanding of this crucial carbon cycle link.
- Identifying key metabolites exchanged between phytoplankton and bacteria is essential for understanding marine carbon cycling.
Purpose of the Study:
- To investigate metabolite exchange between marine plankton using a bacterial-diatom model system.
- To identify specific compounds mediating trophic interactions between diatoms and bacteria.
- To elucidate the role of novel metabolites in marine biogeochemical cycles.
Main Methods:
- Utilized transcriptional patterns in a co-culture system of a Roseobacter bacterium and the diatom Thalassiosira pseudonana.
- Employed vitamin B12 auxotrophy as a sensitive assay for metabolite exchange.
- Analyzed gene expression, quantified metabolite abundance in diatom cytosol and seawater, and performed transcript analysis on North Pacific samples.
Main Results:
- Identified 2,3-dihydroxypropane-1-sulfonate (DHPS) as a highly upregulated metabolite (up to 374-fold) in bacteria co-cultured with diatoms.
- DHPS was found to be a major component of T. pseudonana cytosol and abundant in a North Pacific diatom bloom.
- Evidence of DHPS catabolism by Roseobacter populations was observed in North Pacific samples, suggesting its role in the marine food web.
- Genes for DHPS catabolism have limited distribution, indicating targeted metabolite provisioning by T. pseudonana.
Conclusions:
- DHPS is a significant diatom-derived metabolite that serves as a key link in trophic interactions between diatoms and bacteria.
- Bacterial transformation of DHPS represents a previously unrecognized, substantial contribution to marine carbon and sulfur cycles.
- This finding highlights the potential for other important, yet unidentified, metabolites to play critical roles in ocean biogeochemistry.
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