Developing a population-state decision system for intelligently reprogramming extracellular electron transfer in Shewanella oneidensis

Abstract

The unique extracellular electron transfer (EET) ability has positioned electroactive bacteria (EAB) as a major class of cellular chassis for genetic engineering aimed at favorable environmental, energy, and geoscience applications. However, previous efforts to genetically enhance EET ability have often impaired the basal metabolism and cellular growth due to the competition for the limited cellular resource. Here, we design a quorum sensing-based population-state decision (PSD) system for intelligently reprogramming the EET regulation system, which allows the rebalanced allocation of the cellular resource upon the bacterial growth state. We demonstrate that the electron output from Shewanella oneidensis MR-1 could be greatly enhanced by the PSD system via shifting the dominant metabolic flux from initial bacterial growth to subsequent EET enhancement (i.e., after reaching a certain population-state threshold). The strain engineered with this system achieved up to 4.8-fold EET enhancement and exhibited a substantially improved pollutant reduction ability, increasing the reduction efficiencies of methyl orange and hexavalent chromium by 18.8- and 5.5-fold, respectively. Moreover, the PSD system outcompeted the constant expression system in managing EET enhancement, resulting in considerably enhanced electron output and pollutant bioreduction capability. The PSD system provides a powerful tool for intelligently managing extracellular electron transfer and may inspire the development of new-generation smart bioelectrical devices for various applications.

Biofilm Biology and Engineering of Geobacter and Shewanella spp. for Energy Applications

“…The presence of both IPTG and AHL activates MtrA expression, which restores the EET pathway and increases electricity output ( Hu et al, 2015 ). In another study, the lux QS system was used to construct a population-state decision system for intelligently reprogramming the EET regulation system ( Li F.-H. et al, 2020 ). The EET-related genes or pathways, such as cymA , shuttle exporter genes or flavin biosynthesis pathway, were located at the downstream of QS system and could be expressed at a certain population-state threshold.…”

“…This system permitted the bacterial growth first and then shifted the metabolic flux form bacterial growth to EET. The engineered strain exhibited a higher EET efficiency and an improved pollutant reduction ability ( Li F.-H. et al, 2020 ).…”

Electron shuttles enhanced the removal of antibiotics and antibiotic resistance genes in anaerobic systems: A review

“…In anaerobic biological treatment systems, the redox process based on extracellular electron transfer (EET) is the main metabolic pathway of microorganisms, and it has been demonstrated that the degradation of pollutants by microorganisms is greatly enhanced with the increase of their EET capacity ( Li F. H. et al, 2020 ). Traditionally, electron transfer in anaerobic systems is dependent on intermediates such as H 2 and formic acid and such electron transfer mechanisms are called interspecies hydrogen transfer (IHT) or mediated interspecies electron transfer (MIET) ( Liu et al, 2018 ; He et al, 2019 ), while the discovery of direct interspecies electron transfer (DIET) has provided new insights for enhanced anaerobic biological treatment ( Summers et al, 2010 ).…”

An electrogenetic toggle switch design

“…The rate at which the bacteria metabolise substrate is therefore correlated with their current output. Synthetic gene networks have been engineered to exploit this relationship in exoelectrogens such as Geobacter sulfurreducens ( 25 ) and Shewanella oneidensis ( 26 ), by controlling expression of enzymes involved in key metabolic pathways. These networks offer the synthetic biologist genetic control of the bacteria’s electronic output.…”