Feasting on Iron


Many species of bacteria use iron as an electron donor for lithotrophic growth and make significant contributions to biogeochemical mineral cycling. This presents a considerable physiological challenge. Rates of iron oxidation are poor and the reaction product ‘rust’ is toxic if produced internally. To overcome these challenges bacteria performing ferrophototrophy have evolved to couple Fe(II)-oxidation outside bacteria with C- and N-fixing pathways inside bacteria. Key to this process is a porin-cytochrome complex, PioAB, that spans the bacterial outermembrane. The complex performs Fe(II)-oxidation at the external cell surface and conducts the electrons released by that process to periplasmic electron acceptors. This project aims to resolve the molecular basis for PioAB Fe(II)-oxidation and electron import across bacterial outer membranes.

The project aims to:

– develop an experimentally verified model of the structure and thermodynamic landscape for electron transfer through PioAB


– reveal residues and cofactors critical to Fe(II)-oxidation by PioA:PioB

Methods including bacterial genetics, protein purification, spectroscopy, protein structure determination and enzyme assay will be used during the project which is supervised by Prof Julea Butt and Prof Tom Clarke. The Butt lab with its strong track record of combining biochemistry and spectroscopy to provide new insights into redox catalysis by metalloproteins will lead on biochemical, spectroscopic and kinetic studies. The Clarke lab has expertise in methods including X-ray diffraction and small angle scattering techniques to resolve protein structure and will lead on structural aspects of the project. Together as a team we hope to gain substantial new molecular understanding of an important contribution to bacterial metabolism.

Informal enquiries to Prof Julea Butt (j.butt@uea.ac.uk) are welcome.


Gupta et al Photoferrotrophs produce a PioAB electron conduit for extracellular electron uptake. mBIO (2019) 10:e02668-02619

Li et al His/Met heme ligation in the PioA outer membrane cytochrome enabling light-driven extracellular electron transfer by Rhodospeudomonas palustris TIE-1. Nanotechnology (2020) 31, 354002

White et al Mechanisms of bacterial extracellular electron exchange. Adv. Microb. Physiol. (2016) 68,87