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

In recent years, the negative environmental and health impacts of mining activities have significantly expanded in Sub-Saharan Africa (SSA) due to large volumes of metal waste. This systematic review identified metal-resistant bacteria, mechanisms and drivers of tolerance, and efficiency of bacterial bioremediation in metal-contaminated soils across SSA. Gaps in the literature and future research directions were also highlighted. We conducted a systematic review and synthesize information from articles published from 2005 to February 2026. 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, highlighting their functional redundancy and multiple bioremediation mechanisms in response to metal stress. The 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 factors, metal chemistry, bacterial genetic and molecular resistance, with certain bacteria demonstrating high metal removal efficiencies under laboratory conditions. Despite these useful findings, this systematic review identified a restricted geographical scope among the studies and limited field-based application, which may limit our understanding of the field application of bacterial bioremediation of metal waste across SSA. However, diverse and indigenous bacterial microbiomes adapted to complex regional conditions present the opportunities to advance bacterial bioremediation through the integration of emerging techniques such as microbial-assisted phytoremediation, nanotechnology and genetic modification.