Effects of chlorophenols on microbial activity and functional diversity: Recent advances in OMICs approaches and soil microbial remediation

Chlorophenols (CPs) are toxic organic contaminants released into the environment through pesticide applications and industrial effluents, posing serious health risks to living organisms. Exposure to CPs can adversely affect the soil microbial community and functional diversity, leading to soil deterioration and contamination. Based on toxicity, environmental persistence, and potential for bioaccumulation, CPs contamination is a global concern that must be addressed promptly to prevent its inevitable effects on soil ecosystem functioning and other living organisms, including humans. The soil microbial population shifts or disappears under higher concentrations of CPs, significantly disturbing microbial diversity and their functions. Further, CPs can disrupt the cell membrane of soil microbes, reducing their number, growth, and enzymatic activities. Furthermore, CPs contamination can impact nutrient cycling processes and reduce the activities of respective microbial enzymes, affecting nutrient availability for microbes and plants. Moreover, certain indigenous and bioaugmented microbial strains have demonstrated significant potential (up to 100 %) for the aerobic and anaerobic degradation of CPs to alleviate their toxic effects on soil microbial communities. OMICs-based approaches can also be applied to develop resistant microbial strains, metabolites, proteins, genes, and CPs-degrading enzymes by regulating their gene expressions with enhanced degradation efficiencies. CPs can be degraded by meta- and ortho-cleavage, catalyzed by specific enzymes such as monooxygenase and dioxygenase, using either hydroquinone or 4-chlorocatechol degradation pathways. In addition, integrating different remediation approaches such as bioaugmentation, biostimulation, organic amendments, phycoremediation, and phytoremediation can significantly enhance CPs degradation in the soil. Thus, in conjunction with other bioremediation approaches, microbial remediation could potentially be deployed to treat CPs-contaminated soils and restore ecosystem functioning.