Elucidating factors necessary to transplant extracellular electron transfer pathways
It is so far not possible to reconstruct extended respiratory chains from native exoelectrogens in other organisms like Escherichia or Pseudomonas strains without tremendous losses regarding electron transfer rates. Hence, an understanding of fundamental parts of the electron transport chains or factors necessary to gain full activity of electron transfer chain components is missing. We hypothesize that this is mostly due to the fact that research regarding necessary components for extended electron transfer builds upon loss-of-function studies in the native exoelectrogenic organism and the subsequent transfer of only factors identified within these loss-of-function screens into the designated host organisms. We could already establish using a gain-of-function approach with a Shewanella oneidensis fosmid library expressed in an E. coli strain, that so far overseen factors seem to have massive influence on electron transfer kinetics. Moreover, we established that typical biotechnological chassis organisms have to be systematically adapted for an obligat respiratory anaerobic physiology. It is the aim of this research project to systematically identify factors necessary for the efficient reconstruction of extended electron transfer chains in typical biotechnological chassis strains. We will establish this by specifically designed gain of function screens and the identification of genomic alterations after specific selection experiments. In the end we aim for an E. coli strain containing the necessary elements for extended electron transfer to an electrode surface that conducts anode-assisted fermentations with competitive space-time-yields compared to established oxic production routines.We teamed up with engineering groups, that also submitted proposals within this priority programme, to establish not only optimized biocatalysts for electrode assisted fermentations but moreover identify limitations, best possible process conditions and reactor geometries for the realization of this sustainable way of biotechnological production.