CdS nanoparticles alleviate photo-induced stress in Geobacter co-cultures

Abstract

To date, there is a general lack of research devoted to light-semiconductive nanoparticle (NP)–syntrophy systems though they are ubiquitous in the earth's near-surface. This study demonstrates for the first time that visible light repressed Geobacter co-cultures, whereas light-excited CdS NPs could alleviate this photo-induced stress. Light-excited CdS NPs generated photoelectron–hole pairs to drive direct interspecies electron transfer (DIET) rather than acting as shades or electrical conduits. The mutant studies and RT-qPCR data revealed that the photoelectron-driven DIET needed involvements of cytochromes Gmet_2896 and OmcS, but required fewer of these two key cytochromes than the systems without CdS NPs. Thus, energy consumption for cytochrome biosynthesis was reduced and the photo-induced stress was alleviated. These findings provide a new mechanistic model of DIET between electron-donating and electron-accepting partners, and broaden the knowledge of near-surface biogeochemical processes in nature and interfacial reactions in photocatalytic biotechnologies.