Engineered bioremediation strategies involve either the addition of growth stimulators (electron
acceptors/donors) to the rhizosphere for reduction of heavy metals or addition of nutrients to the
contaminated soil for enhancement of microbial growth and bioremediation properties of
microorganisms or genetically modified plants [144]. Many engineered bacteria with heavy metal
reduction capacity through the expression of improved enzymes like chromate and uranyl reductase were
applied in a specific rhizosphere to perform a specific function. Similarly, genetically modified plants
are also known to produce specific compounds which may support the rhizospheric transformation of
heavy metals. Recently, several researchers have applied these approaches to remediate heavy
metal-contaminated soils using the rhizosphere ecosystem.