PostDoctoral Research Fellowship

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.