Bacteria in bioremediation of metal waste‑contaminated soils across sub‑saharan Africa: mechanisms, driving factors, and efficiency

Abstract

In recent years, the negative environmental and health impacts of mining activities have significantly increased across Sub Saharan Africa (SSA) due to large volumes of metal waste. This systematic review examined metal resistant bacteria, their mechanisms and drivers of tolerance, and the efficiency of bacterial bioremediation in metal contaminated soils across SSA. We synthesized information from articles published between 2005 and February 2026, highlighting gaps in the literature and future research directions. Our results documented 26 types of metal waste generated from mining across SSA, with heavy metals predominating (87.4%). Notably, members of the Bacillus and Pseudomonas genera were prevalent across multiple metals, underscoring their functional redundancy and diverse bioremediation mechanisms under metal stress. Bacteria associated with Pb and Cd showed a high pairwise Jaccard similarity index (0.78). The most frequently reported driving factors of bacterial bioremediation included environmental conditions, metal chemistry, and bacterial genetic and molecular resistance, with certain strains demonstrating high metal removal efficiencies under laboratory conditions. Despite these useful findings, the review identified a restricted geographical scope and limited field based applications, which may constrain our understanding of bacterial bioremediation in real world contexts. However, diverse and indigenous bacterial microbiomes adapted to complex regional conditions present opportunities to advance bioremediation through integration with emerging techniques such as microbial assisted phytoremediation, nanotechnology, and genetic modification.

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