Exogenous Electroactive Microbes Regulate Soil Geochemical Properties and Microbial Communities by Enhancing the Reduction and Transformation of Fe(III) Minerals

Electroactive microbes can conduct extracellular electrontransferand have the potential to be applied as a bioresource to regulatesoil geochemical properties and microbial communities. In this study,we incubated Fe-limited and Fe-enriched farmland soil together withelectroactive microbes for 30 days; both soils were incubated withelectroactive microbes and a common iron mineral, ferrihydrite. Ourresults indicated that the exogenous electroactive microbes decreasedsoil pH, total organic carbon (TOC), and total nitrogen (TN) but increasedsoil conductivity and promoted Fe-(III) reduction. The addition ofelectroactive microbes also changed the soil microbial community from Firmicutes-dominated to Proteobacteria-dominated.Moreover, the total number of detected microbial species in the soildecreased from over 700 to less than 500. Importantly, the coexistenceof N-transforming bacteria, Fe-(III)-reducing bacteria and methanogenswas also observed with the addition of electroactive microbes in Fe-richsoil, indicating the accelerated interspecies electron transfer offunctional microflora. By enhancingsoil Fe-(III) reduction and electron transfer,exogenous electroactive-microbes drive the cooperation of complexmicroflora, thus affecting the fate of soil carbon and nitrogen.

Automated summary

Electroactive microbes can regulate soil geochemical properties and microbial communities through extracellular electron transfer. This study incubated Fe-limited and Fe-enriched farmland soil with electroactive microbes and a common iron mineral. The results showed that the addition of electroactive microbes decreased soil pH, TOC, and TN, increased soil conductivity, and promoted Fe-(III) reduction.