Bioremediation of Heavy Metal-Contaminated Soil Using Engineered Bacterial Consortia

Background: Heavy metal contamination of agricultural and industrial soils is a persistent global problem, and engineered or
rationally assembled bacterial consortia are increasingly proposed as scalable alternatives to physicochemical remediation.
Objective: This review synthesises published evidence on the mechanisms, genetic engineering strategies, and field performance of
engineered bacterial consortia for heavy metal bioremediation of soil. Methods: A narrative review of peer-reviewed studies
identified via PubMed, Google Scholar, and Crossref, covering metal-resistance physiology, genetic engineering approaches (surface
display, metallothionein fusion, biosensor-linked operons), consortium design, and pilot/field trials. Findings: Native resistance
systems (efflux pumps, metallothioneins, extracellular polymeric substances) in strains such as Cupriavidus metallidurans CH34
and Deinococcus radiodurans have been engineered to enhance sequestration of cadmium, lead, chromium, mercury, and arsenic,
with single-strain removal efficiencies of 68-95% reported under controlled conditions; multi-metal and field settings typically
show 20-40% lower performance. Rationally designed consortia exploiting division of labour and plant-growth-promoting synergy
improve robustness relative to monocultures. Conclusions: Engineered consortia hold real promise for soil bioremediation, but
reproducibility across metal mixtures, soil types, and scales remains the principal barrier to deployment.