Effects of long-term and incremental exposure to toxic pollutants on the current generation and microbial communities of electrochemically active bacteria

Electrochemically active bacteria (EAB) serve as catalysts for microbial electrochemical systems, enabling simultaneous wastewater treatment and electricity generation. The increasing presence of toxic pollutants in wastewater may inhibit EAB metabolism and decrease EAB abundance. However, the detailed effects and microbial adaptability remain unclear. The study used two toxic pollutants to simulate long-term and incremental toxic exposure. The study's results show that the current generation of EAB is obviously inhibited at the early stage of toxic exposure, but the inhibition becomes less severe in the middle stage and disappears by the end stage. As a result, EAB are able to resist concentrations of 12 mg L⁻¹ HgSO₄ or 240 mg L⁻¹ CH₂Cl₂. This increased resistance is due to the adaptive response that occurs in EAB. The susceptible Geobacter population decreases while the resistant Geomonas population increases, but the total sum of the two genera remains unchanged. These findings provide insight into the adaptive mechanism of EAB to toxic exposure, which offers a basis for using EAB to treat toxic wastewater.