PhD project strategic theme: Biosciences for renewable resources and clean growth

Photosynthesis is the primary means by which energy enters living organisms and ecosystems. However, organisms that rely on solar energy to carry out cellar processes (phototrophs) sacrifice overall solar-to-biomass conversion in favour of other survival strategies. There are many physical known mechanisms behind this energy loss, but one of the least well understood is the apparent export of energetic electron carriers out of photosynthetic microorganisms, a phenomenon referred to as (exo)electrogenesis.

Understanding exoelectrogenesis is important at a fundamental level, to better understand the biological process that sustains life on Earth. Additionally, understanding this pathway has ramifications for the intelligent design of semi-artificial photosynthetic devices for solar electricity and solar fuel production. Biophotovoltaic devices employ photosynthetic microorganisms to produce electricity from water and sunlight. Unlike conventional photovoltaics, biophotovoltaics do not rely on expensive or extracted materials, however they currently have a limited power output due to inefficient "wiring" between cell and electrode. Similarly, photomicrobial fuel cells employ phototrophic microorganisms to generate liquid fuels from sunlight, water and other simple chemicals, a technology that is much needed in the global transition away from fossil fuels. These technologies rely on the transfer of electrons between electrodes and cells, and a better understanding of this process is essential to overcoming their current limitations.

In the study of extracellular electron transfer, electrochemical techniques are favoured for their ability to probe the thermodynamics and kinetics of electron transfer events. Electrochemistry has proven powerful in studying systems intended for biophotovoltaic application and can be used to infer mechanism of electron transfer to a sub-second temporal resolution. However, it is limited in its ability to provide visual information on the processes involved in electron transfer or resolve these processes spatially. Fluorescence microscopy techniques are well suited to addressing this gap, as they can provide visual information on subcellular systems at increasingly high temporal and spatial resolution.

The project will focus on the visualisation and characterisation of the photosynthetic biofilm-electrode interface during charge transfer processes, exploring the use of chemical biology and electrochemical methods such as in situ confocal fluorescence, total internal reflection fluorescence and Raman microscopy. This will be complemented by the use of super resolution microscopy techniques such as structured illumination microscopy. The aim will be to gain a better understanding of the poorly defined biological phenomenon of light-induced current generation by photosynthetic biofilms, and ultimately to rationally enhance the 'wiring' between the biofilm and the electrode. The project will be highly interdisciplinary and will involve chemical and biophysical characterisations of both synthetic (dyes and electrode materials) and biological systems (proteins, sub-cellular components and bioengineered cells).