Sulfur is a vital macroelement for soil fertility and crop growth, and its bioavailability is converted with electron flux. To determine the effect of biological electron transfer on the sulfur cycle in soil, a microbial electrochemical system (MES) was established to amplify the efficiency of extracellular electron transfer. Results showed that biocurrent obviously promoted the reduction of water‐soluble SO 4 2‐ to S 2− , and...