| NSF Org: |
OPP Office of Polar Programs (OPP) |
| Recipient: |
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| Initial Amendment Date: | June 17, 2011 |
| Latest Amendment Date: | April 9, 2014 |
| Award Number: | 1103503 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Peter Milne
OPP Office of Polar Programs (OPP) GEO Directorate for Geosciences |
| Start Date: | January 15, 2012 |
| End Date: | December 31, 2014 (Estimated) |
| Total Intended Award Amount: | $138,540.00 |
| Total Awarded Amount to Date: | $197,140.00 |
| Funds Obligated to Date: |
FY 2014 = $58,600.00 |
| History of Investigator: |
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| Recipient Sponsored Research Office: |
San Diego CA US 92121-1118 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
San Diego CA US 92121-1118 |
| 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): |
ANT Organisms & Ecosystems, POST DOC/TRAVEL |
| 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): | 47.078 |
ABSTRACT
Conventional wisdom holds that the productivity of Antarctic phytoplankton is controlled by limitation of the trace metal Fe, provided there is sufficient light to support photosynthesis. This study involves the investigation of additional micronutrient (trace metal) requirements, specifically cobalamin (vitamin B12), for the growth of eukaryotic algae (e.g. diatoms, prymnesiophytes) commonly found in abundance in polar waters. Past approaches to this question have stressed either the biogeochemical understanding the marine chemistry and chemical transformation of physiologically active elements such as cobalt, or targeted biochemical and molecular biological studies of the metabolism of this micronutrient as utilized by phytoplankton. Both of these disciplinarily distinct approaches are needed to fully understand the effects trace metal limitation may have on community composition of phytoplankton in the Antarctic. In turn, understanding micronutrient controls on ecosystem productivity are needed to interpret carbon fixation and export rates of the marine carbon cycle in these highly productive waters, and how these may change .
A key aspect of the study is to derive specific protein biomarkers for vitamin B12 stress in vitro, and in turn use these to explore cobalamin stress in field situations. Using RNAi cell lines, the researchers will conduct physiological assays at low and high concentrations of vitamin B12 to follow expression profiles of two potential B12-trafficking proteins. These experiments should shed light on how these proteins are involved in acquisition and metabolism of B12. Additionally the subcellular localization of proteins involved in B12 metabolism will be studied using fluorescent fusion tags. High resolution transcriptomic analyses of Antarctic diatom cultures under high and low B12 concentrations will be performed to assess whether proteins are regulated by B12 availability.
PUBLICATIONS PRODUCED AS A RESULT OF THIS RESEARCH
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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.
Diatoms are an important group of photosynthetic organisms that inhabit the sunlit surface ocean across much of the globe. These microscopic organisms are responsible for a large portion of oxygen production on Earth and consume carbon dioxide in that process. In parts of the Southern Ocean around Antarctica, diatom growth can be limited by the availability of vitamin B12. Just like humans, these diatoms use B12 to conduct important chemical reactions that are required for survival and growth. Also like humans, diatoms can’t make their own B12 so rely on bacteria to produce it for them. Work conducted in this Fellowship has improved our understanding of how diatoms acquire the vitamin, what they use it for, and what processes determine when and where they can be B12 deficient in the ocean. By manipulating diatom genomes and measuring gene expression in diatoms under B12 starvation, we identified proteins involved in B12 uptake and those used to reduce B12 requirements. We also showed that the expression of diatom genes encoding these B12 starvation indicator proteins is high in Southern Ocean environments. Since bacteria are the ultimate source of B12 for diatoms, we designed an experiment to identify which bacteria produce and consume B12 in the Southern Ocean and how those bacteria interact with diatoms. This work showed that B12 limitation occurs seasonally in Southern Ocean diatoms and is driven by a series of tiered interactions between diatoms and bacteria that are structured, in part, by iron availability. The hypotheses and tools developed during this Fellowship will enable oceanographers to better understand when, where and why primary production is vitamin- limited in the ocean.
Last Modified: 04/01/2015
Modified by: Erin M Bertrand
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