Microbial remediation mechanisms and applications for lead-contaminated environments

High concentrations of lead (Pb) in agricultural soil and wastewater represent a severe threat to the ecosystem and health of living organisms. Among available removal techniques, microbial remediation has attracted much attention due to its lower cost, higher efficiency, and less impact on the environment; hence, it is an effective alternative to conventional physical or chemical Pb-remediation technologies. In the present review, recent advances on the Pb-remediation mechanisms of bacteria, fungi and microalgae have been reported, as well as their detoxification pathways. Based on the previous researches, microorganisms have various remediation mechanisms to cope with Pb pollution, which are basically categorized into biosorption, bioprecipitation, biomineralization, and bioaccumulations. This paper summarizes microbial Pb-remediation mechanisms, factors affecting Pb removal, and examples of each case are described in detail. We emphatically discuss the mechanisms of microbial immobilization of Pb, which can resist toxicity by synthesizing nanoparticles to convert dissolved Pb(II) into less toxic forms. The tolerance mechanisms of microbes to Pb are discussed at the molecular level as well. Finally, we conclude the research challenges and development prospects regarding the microbial remediation of Pb-polluted environment. The current review provides insight of interaction between lead and microbes and their potential applications for Pb removal.