Using cryo-EM and biophysics to understand how bacterial photosynthesis powers a range of cellular processes

Photosynthesis provides energy to sustain almost all known life and has enormous untapped potential for green biotechnology. However, to meet the growing demand mankind places on photosynthesis, we must improve phototrophic organisms' ability to use the energy of sunlight to produce useful products. Purple anoxygenic phototrophic bacteria are metabolically versatile organisms widely used in applications such as wastewater treatment and production of high-value chemicals. Energy to power these costly biochemical processes can be provided by photosynthesis, meaning these organisms are of interest for green biotechnology.

The structure and function of the light-harvesting complexes and the reaction centre, and the cytochrome bc1 complex have been the subject of intense study over many years, leading to a detailed molecular understanding of how these systems work in concert to provide energy for the cell. However, surprisingly little is known about how the photosynthetic electron transport chain is linked to other metabolic pathways, raising the question of how photosynthesis in these bacteria ultimately powers processes like carbon and nitrogen fixation.

This project will use a combination of biochemistry, spectroscopy, and cryogenic electron microscopy to understand how electrons are delivered to the photosynthetic electron transport chain from the environment, and then delivered to downstream cellular processes to produce useful products. Working in the model purple phototrophic bacterium Rhodopseudomonas palustris, the way in which electrons are delivered to the reaction centre from extracellular ferrous iron via membrane-spanning heme wires, and shuttled from the cytochrome bc1 complex to the dentification pathway via nitric oxide reductase will be investigated. Experiments will focus on the mobile electron carriers which "wire" the complexes together yet remain poorly understood. Therefore, detailed biochemical and structural studies of how these mobile electron carriers interact with their binding partners will begin to elucidate how a range of cellular processes are wired to photosynthesis