No abstract

Conventional biodecolorization of azo dyes is often limited by the lack of sustainable and bioavailable electron donors in aqueous environments. This limitation may be overcome by light-excited photoelectrons that drive the microbial reduction of azo dyes. Here, we innovatively developed a surface-precipitated Geobacter sulfurreducens− CdS biohybrid for the bioreduction of methyl orange (MO), a typical azo dye, driven by light. This biohybrid system exhibited the maximum kinetic constant at 1.441 h −1 , which is, to the best of our knowledge, the highest value reported thus far for MO biodecolorization. The intermittent illumination results indicated that G. sulfurreducens could directly use extracellular photoelectrons (rather than electrons from organics oxidization by strains) in order to perform decolorization on the bacterial cell surface. This can be attributed to the direct electron transfer from CdS nanoparticles to G. sulfurreducens. In addition, OmcB was identified as a key outermembrane protein that may act as a capacitor to modulate electron transfer from CdS to MO. This biohybrid catalytic approach may serve as a new strategy for azo dye degradation in oligotrophic surface waters and can deepen our knowledge on interactions between light, semiconductors and micro-organisms.

No abstract

No 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.

Nanosized titanium dioxide (TiO2) is a naturally existing nanoscale semiconducting mineral, and its co-occurrence with microbes may elicit differential environmental effects. In this study, the impacts of TiO2 nanoparticles (NPs) on the reductive dissolution of As­(V) and Fe­(III) from flooded arsenic-enriched soils were examined under intermittent illumination and dark conditions. The amendment with TiO2 NPs under intermittent illumination resulted in the highest As/Fe reduction among all amendments. In the amendment with TiO2 NPs, the maximum concentrations of Fe­(II) derived from intermittent illumination and dark treatments were nearly 2.1- and 1.7-fold higher than the soils amended with acetate alone under dark conditions (36.5 ± 4.5 mg/L), respectively, and nearly 1.6- and 1.2-fold higher than the increased As­(III) concentrations (8175.2 ± 125.5 μg/L) detected under the same conditions. However, the removal of total organic carbon derived from the amendment with acetate-TiO2 NPs under intermittent illumination was only 0.8 times that of the amendment with acetate alone under dark conditions. Because TiO2 NPs are highly responsive to sunlight, more photoelectrons supplied from intermittently illuminated soils were separated synchronously by accompanying them with the capture of photoholes by humic/fulvic acids; thereafter, the photoelectrons participated in As­(V)/Fe­(III) reduction. In addition, the electrical conductivities of TiO2 NPs-supplemented soil particles were nearly 1.6-fold higher than that of nonsupplemented samples, thereby enabling a long-distance electron transfer. Moreover, the amendment with TiO2 NPs with intermittent illumination resulted in an increase to the abundances of several metal-reducing bacteria in the soil microbial community, e.g., Bacillus, Thermincola, Pseudomonas, and Clostridium, correspondingly boosting the involved microbial degradation of organic substrates to supply more bioelectrons for As­(V)/Fe­(III) reduction. The findings have an important implication on the understanding of the role of nanosized minerals in the biogeochemical cycling of metal pollutants.

• CdS NPs assists hybrid microbialphotoelectrochemical processes. • CdS NPs display desirable biocompatibility with microorganisms. • CdS NPs-immobilized biohybrids display a potential for environmental application.

Methanogen–semiconductor biohybrids drive the sustainable conversion of microplastics into CH4 under illumination, as reported by Shungui Zhou, Yujie Xiong, and co‐workers in their Research Article (e202213244). The biotic–abiotic hybrid system not only addresses a long‐standing challenge of photocatalysis by fully utilizing photogenerated electrons and holes without the need for unsustainable chemical sacrificial quenchers, but also provides clues for a better understanding of the global carbon cycle.