Recent advances in the roles of minerals for enhanced microbial extracellular electron transfer

Abstract

Minerals are ubiquitous in the natural environment and have close contact with microorganisms. In various scenarios, microorganisms that harbor extracellular electron transfer (EET) capabilities have evolved a series of beneficial strategies through the mutual exchange of electrons with extracellular minerals to enhance survival and metabolism. These electron exchange interactions are highly relevant to the cycling of elements in the epigeosphere and have a profound significance in bioelectrochemical engineering applications. In this review, we summarize recent advances related to the effects of different minerals that facilitate the EET process and discuss the underlying mechanisms and outlooks for future applications. The promotional effects of minerals arise from their redox-active ability, electrical conductivity and photocatalytic capability. In mineral-promoted EET processes, various responses have concurrently arisen in microorganisms, such as stretching of electrically conductive pili (e-pili), upregulated expression of outer-membrane cytochromes (Cyts) and production of specific enzymes, and secretion of extracellular polymeric substances (EPSs). This review synthesizes the understanding of electron exchange mechanisms between microorganisms and minerals and highlights potential applications in development of renewable energy production and pollutant remediation, which are topics of particular significance to future exploitation of biotechnology.

Modular configurations of living biomaterials incorporating nano-based artificial mediators and synthetic biology to improve bioelectrocatalytic performance: A review

“…Transmittance-based transient absorption and time resolved infrared spectroscopy are able to clearly elucidate the lifetime of charge uptake and discern the pathways of photoexcited electrons directly feeding into membrane-bound proteins in several EAB-semiconductor NP hybrid biomaterials (Kornienko et al, 2016). Photosynthetic living hybrid biomaterials may configure through pairing various host EABs or enzymes (e.g., Geobacter sulfurreducens, Escherichia coli and catalase) with specific semiconductors (e.g., CdS, TiO 2 and InP NPs) (Cestellos-Blanco et al, 2020;Dong et al, 2020a). This implies that semiconductor NPs featuring large surface areas enable an intimate interaction with EABs contributing to microbial metabolism for enhanced biochemical reactions.…”

“…The field of BESs involving the harvest of electrons from microbial energy metabolism has made several impressive advances in the past decade (Martinez and Alvarez, 2018). BESs have contributed many scientific and technological applications, including bioremediation of pollutants, bioleaching, renewable and carbon neutral energy production and biosensing (Dong et al, 2020a;Liu et al, 2018). However, inefficient electron transfer at interfaces between EABs and extracellular electrodes often become a bottleneck that limits the widespread application of BESs (Patil et al, 2012;Popat and Torres, 2016).…”

Perspectives on Potential Applications of Nanometal Derivatives in Gaseous Bioenergy Pathways: Mechanisms, Life Cycle, and Toxicity

“…Extracellular electron transfer (EET) in anaerobic media is carried out either via biotic–biotic or biotic–abiotic interactions. Biotic–biotic relationships (or more specifically interspecies electron transfer: IET) refers to electron-sharing mechanisms between syntrophic microorganisms within the microbiome associated with AD. ,,, IET is subdivided into mediated and direct interspecies electron transfer (MIET and DIET). In the case of the MIET mechanism, electron transfer occurs via soluble mediators that are first generated and released by fermenting, and acidogenic bacteria diffuse in the media and are finally consumed by methanogens in a syntrophic relationship. , On the other hand, the DIET mechanism involves the exchange of electrons between microbial cells through electrical conductors located at the outer cell membrane, i.e., conductive pili (biotic nanowires), without the need for mediators. , Regarding the biotic–abiotic relationship, this relation has been categorized, based on the direction of electron flow, either as inward or outward the microbe.…”

“…Biotic−biotic relationships (or more specifically interspecies electron transfer: IET) refers to electron-sharing mechanisms between syntrophic microorganisms within the microbiome associated with AD. 18,19,22,23 IET is subdivided into mediated and direct interspecies electron transfer (MIET and DIET). In the case of the MIET mechanism, electron transfer occurs via soluble mediators that are first generated and released by fermenting, and acidogenic bacteria diffuse in the media and are finally consumed by methanogens in a syntrophic relationship.…”

High-Efficiency Ethanol Yield from Anaerobic Fermentation of Organic Wastes via Stimulating Growth of Ethanol-Producing Fe(III)-Reducing Bacteria with Magnetite

“…9 This was supported by the experimental phenomenon that Geobacter species grew on the electrodes with a potential lower than −0.15 V, and more positive potentials did not support them to yield more cells. 16,39 Based on these considerations, magnetite (mainly Fe 3 O 4 , E Fe 3 O 4 /Fe 2+ = −0.314 V, pH = 7.0) was utilized as an extracellular Fe(III) source to stimulate the growth of ethanol-producing Fe(III)-reducing bacteria, and the current study proposed a promising strategy for achieving highefficiency ethanol production from anaerobic fermentation of organic wastes in mixed cultures under the acidic conditions with magnetite. In addition to the performances of ethanol production, high-throughput sequencing and fluorescence in situ hybridization (FISH) were used to analyze the abundance and amount of ethanol-producing Fe(III)-producing bacteria, with the aim of further evaluating this strategy.…”