Practice question

Bioremediation encompasses deliberate application of biological agents including bacteria, archaea, fungi and plants to neutralize, transform, degrade or immobilize environmental pollutants, ultimately converting hazardous organics into less harmful end products such as carbon dioxide, water, chloride and inorganic salts. Indigenous genera Pseudomonas, Sphingomonas, Rhodococcus harbor catabolic plasmids TOL encoding toluene degradation, OCT for octane, NAH for naphthalene, and chromosomal genes nahAc non-heme iron dioxygenase, alkB integral membrane alkane hydroxylase, xylE catechol 2,3-dioxygenase that initiate oxidative attack. Mycoremediation using Phanerochaete chrysosporium exploits lignin peroxidase to oxidize recalcitrant polycyclic aromatic hydrocarbons. Unlike chemical precipitation requiring lime addition producing sludge, incineration generating dioxins with high energy cost, or physical removal via excavation, bioremediation exploits natural metabolic pathways under ambient temperature, operates in situ minimizing disturbance or ex situ with control, and can be enhanced via bioaugmentation, biostimulation or engineered strains expressing expanded substrate ranges. Applications span oil spills, chlorinated solvents, heavy metals via biosorption and radionuclides via bioprecipitation, representing sustainable ecosystem restoration strategy.