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Our research

How do bacteria control electron flow inside the cell and how can we tap into this reducing power for biotechnological purposes?

In the Fixen lab, we are working to understand intracellular electron flow in the anoxygenic phototroph, Rhodopseudomonas palustris, by characterizing components of electron transfer and how they are regulated by changes in the environment.


Redox regulation of metabolism in an anoxygenic phototroph

Under anaerobic conditions, Rhodopseudomonas palustris (R. pal) generates energy from light using one of the simplest forms of photosynthesis, cyclic photophosphorylation, and it can modulate the components of its photosystem in response to changes in light intensity. We have found that the intracellular redox status of R. pal is altered in response to low light intensity. This has put us in a position to study mechanisms by which redox status can modulate central metabolism and product formation without the complication of reactive oxygen species. In collaboration with scientists at the Pacific Northwest National Laboratory (PNNL) and the Environmental Molecular Sciences Laboratory user facility at PNNL, we are using proteomic approaches to identify redox sensitive proteins in R. pal. From initial results, we have evidence that several enzymes that are important for bioenergy production may be sensitive to redox regulation. These could be targets for optimization of pathways important for bioenergy production.

The role of electron carrier proteins in an anoxygenic phototroph

In order to understand intracellular electron flow, we must understand the role and regulation of electron carrier proteins. Some of these electron carrier proteins, such as ferredoxin and flavodoxin, act as “wires” in the cell, carrying electrons from an electron donor to an electron acceptor. Other electron carrier proteins, such as thioredoxin and glutaredoxin, act as posttranslational regulators of metabolic pathways in response to cellular redox status. The Fixen lab is working to understand how these electron carrier proteins function in an anoxygenic phototroph by understanding their regulation and role as the cellular redox status changes.

Harnessing aromatic compound degradation for bioremediation and improved bioconversion of lignocellulosic biomass

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