| NSF Org: |
OCE Division Of Ocean Sciences |
| Recipient: |
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| Initial Amendment Date: | September 17, 2012 |
| Latest Amendment Date: | September 17, 2012 |
| Award Number: | 1226165 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Judith Pugh
gpugh@nsf.gov (703)292-7589 OCE Division Of Ocean Sciences GEO Directorate for Geosciences |
| Start Date: | March 1, 2013 |
| End Date: | February 28, 2015 (Estimated) |
| Total Intended Award Amount: | $170,000.00 |
| Total Awarded Amount to Date: | $170,000.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
Berkeley CA US 94705-2045 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
Cambridge MA US 02139-4308 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | OCE Postdoctoral Fellowships |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
In this project, the investigator combines field research and bioinformatics to describe and quantify Prochlorococcus mixotrophy in different cultured ecotypes as well as uncultivated populations and incorporate this into a global ecosystem model.
In order to understand and accurately predict the complex relationships between climate and the carbon cycle, climate models must account for the critical role of the microbes that mediate significant carbon reservoirs in the ocean. Current models do not reflect the important ecological or functional richness of marine microbial communities. One important marine bacterium that should be included in these models is the marine phototrophic cyanobacterium Prochlorococcus. It is the most abundant oxygenic phototroph in the world's tropical and subtropical oligotrophic oceans and is responsible for a sizable fraction of marine carbon fixation in these areas. This project will examine in detail one aspect of how this organism contributes to carbon cycling, through organic carbon uptake, which is more generally referred to as mixotrophy in phototrophic bacteria. This important process is poorly understood, and has not been incorporated into marine ecosystem and biogeochemistry models that describe carbon flow, even though it has been shown to be prevalent among certain marine phototrophs, especially Prochlorococcus.
The broader impacts include educational activities for undergraduates and K-12 students. Through the MIT summer research program for minority undergraduates, the investigator will develop programming and statistics curricula and work in the laboratory as a mentor to these students. Through the Edgerton Center's programs for K-12 education, the investigator will teach students about the importance of marine ecosystems in maintaining a healthy climate and what is being done to understand it better. In addition, research results will contribute to a better understanding of the future climate by providing an oceanic ecosystem model that includes an important process that has not previously been modeled, cyanobacterial mixotrophy.
This project is supported under the NSF Ocean Sciences Postdoctoral Research Fellowship (OCE PRF) program, with goals to support novel research by early career scientists and increase the diversity of the U.S. ocean sciences workforce and research community. With OCE-PRF support, this project will enable a promising early career researcher to establish themselves in an independent research career related to ocean sciences and broaden participation of under-represented groups in the ocean sciences.
PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
Project Outcomes
Marine picocyanobacteria are the most abundant primary producers in the world’s oceans. They account for a large part of marine carbon fixation, assimilation of carbon dioxide into cell material. This makes them incredibly important participants in the carbon cycle and thus in understanding climate change. Over the past two decades researchers have discovered that these photosynthetic bacteria can sometimes take up organic carbon (mixotrophy) in lieu of carbon dioxide. This means that they may transiently emit carbon dioxide, altering our perception of their role in carbon cycling and in the marine microbial community in general. This study aimed to characterize and quantify this trait in order to better understand carbon cycling in the oceans and evolution in ocean microbial communities.
This project characterized and quantified the genetic potential for organic carbon uptake among marine picocyanobacteria, using DNA sequencing data from sixty-seven laboratory strains and from marine samples from sixty-eight sites from around the world. The ocean samples covered four oceans and two major seas from up to three depths per site. Quantification of amino acid, peptide, and sugar transporters in this group of samples and genomes indicate that organic carbon uptake is a ubiquitous trait. The genes for uptake are found in all laboratory strains and in all of the environmental samples. This suggests that most, if not all, marine picocyanobacteria in the wild take up organic carbon.
Quantification of these genes also indicated that certain groups of marine picocyanobacteria have a capacity to take up a wider range of organic carbon compounds than others. Picocyanobacteria isolated from darker, higher nutrient, more variable environments had the capacity to take up more types of organic compounds. This tendency was validated by the environmental data, which showed that samples in coastal areas harbored picocyanobacteria with a wider variety of organic compound uptake genes compared to open ocean samples. Samples with higher nutrient concentrations along a nutrient gradient in the Pacific Ocean also contained genomes with higher numbers of organic compound uptake genes than samples with lower nutrient concentrations.
The differential genetic capacity for nutrient uptake among picocyanobacteria indicates that they evolved to take better advantage of organic compounds in environments where a variety of organic nutrients were more readily available (high nutrient environments and highly variable environments) and where light limitation made supplemental carbon and energy sources essential (low light environments). This suggests that the selection pressures for picocyanobacterial organic compound uptake differ from those that promote mixotrophy in larger photosynthetic organisms such as dinoflagellates, which often use mixotrophy in very low nutrient environments.
Outreach
The primary outreach project of this PI (Alexis Yelton) consisted of beginning a group for female marine scientists that seeks to make women in the field more visible, more connected to each other, and helps start a dialog to address the lack of promotion and retention of women in marine science. The group, the Society for Women in Marine Science (SWMS) held its first workshop in September 2014. This workshop brought together almost one hundred women from MIT, the Woods Hole Oceanographic Institution, the University of Rhode Island, Boston University, the US Geological Survey, the University of Massachusetts Boston, and the University of Massachusetts Dartmouth. At the workshop, the participants and speakers discussed challenges they faced in academia as well as solutions they had developed.
On October 10, 2015...
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