P-140 - Microbial electricity production: Biomolecular elucidation of extracellular electron transfer mechanisms of Geobacter metallireducens

Abstract

Geobacter bacteria have been inspiring the development of many biotechnological applications, particularly in the fields of bioenergy and bioremediation [1]. G. metallireducens (Gm) bacteria exhibit further interesting physiological features compared to G. sulfurreducens (Gs) [2], and despite the enormous potential for practical applications, much less is known about the structural and functional properties of Gm electron transfer components. In this work, a key cytochrome from G. metallireducens (PpcA) was studied in detail for the first time using complementary biochemical and biophysical techniques, including UV-visible, CD and NMR spectroscopy. The results showed that the cytochrome contains three low-spin c-type heme groups with His-His axial coordination, a feature also observed for its homologue in Gs. However, despite the high sequence homology between the two cytochromes, this study revealed important structural and functional differences that include the relative orientation of the hemes and working redox potential windows. Overall, the data obtained paved the way to understand the extracellular electron transfer mechanisms in G. metallireducens.