Mechanism And Application Of Cadmium Sulfide Nanoparticles Alleviating Photo-induced Stress In Geobacter

Geobacter has the unique ability to transfer extracellular electrons and is an important microorganism to drive the biochemical reactions of the earth.To date,most researches on Geobacter carried out under the dark environment.However,due to the ubiquity of sunlight and the wide application of catalytic bioreactor,Geobacter are unavoidable to be exposed to light.Photocatalytic semiconductive nanoparticles?NPs?are ubiquitous in nature.Among them,cadmium sulfide?CdS?NPs can produce photoelectrons within the wavelength coverage of visible light,so they are often applied in photobiological systems and coexist with Geobacter.Based on the above,mechanisms of visible light and CdS NPs on the growth and metabolism of Geobacter sulfurreducens and the interspecies electron transfer of Geobacter co-cultures were studied,and a cost-effective technique for treating dye wastewater with Geobacter was developed.Main results of this paper are as follows:?1?The visible light repressed the growth and metabolism of Geobacter sulfurreducens.CdS NPs repressed the growth and metabolism of Geobacter sulfurreducens in the dark environment,whereas photoelectrons generated by CdS NPs under visible light could alleviate this photo-induced stress on Geobacter sulfurreducens.The mutant studies showed that OmcS and PilA protein play an important role in the photoelectron uptake of Geobacter sulfurreducens.?2?The visible light repressed the Geobacter co-cultures,whereas amendment of CdS NPs could alleviate this photo-induced stress.Mutant experiments revealed that this alleviating mechanism was caused by photoelectron-hole pairs generated by light-exciting CdS NPs.Photoelectron-hole pairs can drive direct interspecies electron transfer?DIET?.The mutant studies and RT-qPCR data revealed that the photoelectron-driven DIET needed involvements of two key cytochromes,Gmet₂896 and OmcS,but required a fewer number of these two cytochromes than those without CdS NPs.Thus,energy consumption for cytochrome biosynthesis was reduced and the photo-induced stress was alleviated.?3?A visible light-CdS-Geobacter sulfurreducens hybrid system was constructed to improve the degradation of amaranth dye wastewater.The hybrid system was 21-fold faster than the visible-CdS system and 4-fold faster than the visible-Geobacter sulfurreducens system and G.sulfurreducens in degrading the amaranth dye.In addition,the hybrid system had good cyclic stability.After three cycles,the degradation efficiency still remained ?75%.The visible light-CdS-Geobacter sulfurreducens hybrid system provides an efficient method for dye wastewater degradation and has broad application prospects.