Carbon Metabolism

Interest in the potential response of global primary production to changes in atmospheric CO₂ has stimulated much research into the physiology and ecology of C₄ versus C₃ photosynthesis in higher plants.  In contrast, the corresponding research questions for marine phytoplankton, which account for 40% of global primary production, have received little attention. Our central hypothesis is that marine diatoms and potentially other marine phytoplankton possess a unicellular C₄ pathway for inorganic carbon acquisition and that this pathway is important in determining the response of marine primary production to variable CO₂ as well as interpretation of ¹³C signals in marine organic matter.  Preliminary work has demonstrated that a C₄ pathway is present in the marine diatom Thalassiosira weissflogii but there is controversy over the magnitude of carbon flux through a C₄ organic pool to RubisCO.  Why diatoms might posses a C₄ pathway in addition to a carbon concentrating mechanism (CCM) has also been questioned.  Using membrane inlet mass spectrometry we have found that diatoms store CO₂ in the form of organic carbon and that this pool can be influenced by inhibitors of the key C₄ pathway enzymes, phosphoenolpyruvate carboxylase (PEPCase) and phosphoenolpyruvate carboxykinase (PEPCKase).  These observations support the view that T. weissflogii concentrates carbon through a C₄ pathway.

 

Below is the most recent annual report regarding this work.