Projects

Recruitment to the NRPDTP and iCASE programmes are now open. The deadline for applications is the 27th November 2017.

02 / 10 / 2017

Discovering how microbes and minerals interact during biological metal respiration (CLARKE_U18DTP)

how to apply

In many lake and marine sediments bacteria can respond to oxygen limiting conditions by using solid minerals and metals as electron acceptors. Unlike most metabolic reactions, this reduction of extracellular mineral substrates must take place outside the cell. This requires electrons generated inside the cell cytoplasm to move across the outer membrane and into the extracellular mineral. The model organism Shewanella oneidensis assembles electron channels in the outer membrane that all electrons to flow through a series of cytochrome proteins onto the cell exterior. The electrons accumulate on the cell surface in exposed cytochromes that, by an unknown mechanism, pass the electrons to mineral substrates.

Electron transfer between cytochrome and mineral involves organic flavin molecules, but it is not clear if these are prosthetic cytochrome cofactors, or transient electron shuttles between microbe and mineral. This PhD will uncover the role of flavins in this electron exchange and so determine the mechanism of mineral reduction in Shewanella. From the onset of the project conditions have been found where cytochromes bind flavin tightly. The student will use a range of cellular labeling methods to determine whether these conditions occur in Shewanella under physiologically relevant conditions. The student will also purify the flavin bound form of the cytochrome and use a range of structural and spectroscopic techniques, including fluorescence and X-ray crystallography, to determine how the flavin bound cytochrome differs from the flavin-free form. By combing both microbiological and biochemical experiments the student will find how Shewanella is capable of reducing minerals.