MICROBE BASED REMEDIATION OF PROBLEMATIC AND POLLUTED SOILS AND ITS CONSEQUENCES IN NUTRIENT CYCLING

Abstract

Microbe-mediated remediation offers a sustainable route for managing problematic and polluted soils, but removing the contaminant does not, by itself, restore soil function. An integrated framework linking microbial stress responses and contaminant transformation to carbon (C), nitrogen (N), and phosphorus (P) cycling in soils affected by heavy metals, petroleum hydrocarbons, pesticides, salinity, alkalinity, and acidity is developed in this review. Key microbial mechanisms—biosorption, bioaccumulation, biomineralization, enzymatic degradation, redox transformation, organic-acid production, siderophore activity, and extracellular polymeric substance formation—are evaluated according to how they alter contaminant bioavailability and the microbial processes that govern nutrient fluxes. It is shown by the comparative synthesis that the link between remediation and nutrient recovery is context dependent: microbial C demand can be raised, and N and P transiently immobilized, by hydrocarbon degradation; N- and P-cycling functions can be reorganized by metal stress; and nutrient availability is improved by correcting pH or salinity only when microbial functional capacity is also restored. Microbial resistance is distinguished from functional recovery, and a complementary set of indicators is proposed: microbial biomass, functional genes, enzyme activities, nutrient pools, contaminant bioavailability, and plant performance. Recent advances—rhizoremediation, microbial consortia, biosurfactants, genome engineering, omics-guided selection, and nano-enabled systems—are assessed for their potential and limitations in restoring soil function. Finally, key knowledge gaps in connecting contaminant fate to process-level C, N, and P recovery are identified, and the need for field-scale validation under realistic soil conditions is stressed.