Biochemistry of bacterial dissimilatory metal reduction

• Applicant: Professor Dr. Johannes Gescher
• Subject Area: Metabolism, Biochemistry and Genetics of Microorganisms
• Term: from 2009 to 2016
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 131646117

Dissimilatory metal reduction is a respiratory process that operates in various Bacteria and Archaea. These microorganisms are able to use oxidized metals like Fe(III), Mn(IV), Cr(VI), or U(VI) as terminal electron acceptors of their anaerobic electron transport chains. Shewanella oneidensis is one of the two model organisms to study this process. However, even after decades of research on dissimilatory metal reduction, the essential minimal protein set for the electron transport to metallic electron acceptors is still unknown. I am pursuing a novel synthetic biology based approach to tackle this problem. Therefore, the goal of the proposed study is to convert Escherichia coli into a dissimilatory metal reducer through expression of potential key genes from S. oneidensis. Using this technique we have already established a strain that is able to respire with chelated Fe(III) as terminal electron acceptor and have thereby shown the applicability of the method. Via the insertion of further genes for possible compounds of the electron transport chain from S. oneidensis we want to proceed to the next level, being to establish an electron transfer to crystalline iron and manganese forms. We will detect potential key players for the reduction chain to ferric iron and manganese using several parallel approaches, which include mass spectrometry, purification and following characterization as well as targeted gene deletions. A series of proof of principle experiments for the reduction chain to ferric iron were already conducted. These in vitro experiments revealed interprotein electron transfer reactions and were also verified by in vivo experiments. The designed E. coli strains are supposed to be further used to address questions of protein localization and complex formation and as a platform for heterologues expression of targets for further crystallization studies.

• DFG Programme: Research Grants