Tailored extracellular electron transfer pathways enhance the electroactivity of Escherichia coli

Abstract

Extracellular electron transfer (EET) engineering in Escherichia coli holds great potential for bioremediation, energy and electrosynthesis applications fueled by readily available organic substrates. Due to its vast metabolic capabilities and availability of synthetic biology tools to adapt strains to specific applications, E. coli is of advantage over native exoelectrogens, but limited in electron transfer rates. We enhanced EET in engineered strains through systematic expression of electron transfer pathways differing in cytochrome composition, localization and origin. While a hybrid pathway harboring components of an E. coli nitrate reductase and the Mtr complex from the exoelectrogen Shewanella oneidensis MR-1 enhanced EET, the highest efficiency was achieved by implementing the complete Mtr pathway from S. oneidensis MR1 in E. coli. We show periplasmic electron shuttling through overexpression of a small tetraheme cytochrome to be central to the electroactivity of this strain, leading to enhanced degradation of the pollutant methyl orange and significantly increased electrical current to graphite electrodes.

Enzymatic and Microbial Electrochemistry: Approaches and Methods

“…Recently, Mouhib et al showed that the complete expression of the Mtr pathway together with periplasmic cytochromes can further enhance electron transfer in engineered E. coli . Conversely from the expression of Shewanella EET pathways, considerably less studies investigated the expression of the G.…”

“…116 Recently, Mouhib et al showed that the complete expression of the Mtr pathway together with periplasmic cytochromes can further enhance electron transfer in engineered E. coli. 117 Conversely from the expression of Shewanella EET pathways, considerably less studies investigated the expression of the G. sulfurreducens EET mechanism due to its higher complexity. Notably, Sekar et al reported the expression of G. sulfurreducens outer membrane cytochrome OmcS in cyanobacteria, enabling a 9-fold current increase.…”

Applying synthetic biology strategies to bioelectrochemical systems

“…They discovered that the highest EET efficiency was achieved by expressing the complete Mtr pathway from S. oneidensis and overexpression of periplasmic cytochromes is essential to the electroactivity of engineered E. coli . [ 43 ]…”

“…They discovered that the highest EET efficiency was achieved by expressing the complete Mtr pathway from S. oneidensis and over-expression of periplasmic cytochromes is essential to the electroactivity of engineered E. coli. [43] In addition to the Mtr pathway, Song and co-workers engineered E. coli with a porin membrane protein OprF from P. aeruginosa PAO1, which significantly improved its membrane permeability, resulting in a much higher current output in microbial fuel cells (MFCs). [44] Additionally, Jäntti and co-workers engineered E. coli with a mannose-binding Fim pili.…”

Implementation of a flavin biosynthesis operon improves extracellular electron transfer in bioengineered Escherichia coli

“…While these mechanisms equip Shewanella species with the efficient EET capabilities necessary for implementation in BES, S. oneidensis MR-1 and other native exoelectrogens are often lacking in their substrate spectrum and genetic amenability to realize specific BES applications. Therefore, E. coli has emerged as a promising alternative to native exoelectrogens for BES applications, and as a target for engineering to enable efficient EET [4,6,[15][16][17][18][19][20][21][22] . Over the past two decades, different [15] , overexpression of the full MtrCAB complex in the outer membrane [16] and co-expression of the inner membrane cytochrome CymA [18] , to the expression of both membrane-associated and periplasmic cytochromes [22] .…”