Isolation and molecular-proteomic characterization of metallothionein-producing heavy metal-resistant bacteria for industrial wastewater bioremediation.

Industrial wastewater is a major source of heavy metal contamination, posing serious environmental and public health risks. In this study, indigenous heavy metal-resistant bacteria were isolated from industrial wastewater and evaluated for their bioremediation potential with a focus on metallothionein (MT) production. A total of 38 bacterial isolates were screened for resistance to lead, cadmium, and nickel, among which Pseudomonas aeruginosa and Bacillus spp. exhibited the highest tolerance levels. Three superior isolates (6M, 8M, and 21F) were selected based on minimum inhibitory and bactericidal concentrations, growth stability, and reproducibility. Molecular analysis confirmed the presence of MT-related genes, and protein profiling by SDS-PAGE revealed MT-associated bands with molecular weights of approximately 6-7 kDa. Metal removal assays demonstrated removal efficiencies of up to 83.4% for Cadmium, 76.9% for Cobalt, and 69.9% for nickel by Bacillus thuringiensis under laboratory conditions. This study provides an integrated evaluation of indigenous industrial wastewater bacteria by correlating metallothionein gene detection, proteomic evidence of low-molecular-weight metal-binding proteins, and quantitative multi-metal removal efficiency within the same isolates. The findings highlight the potential application of these strains in heavy metal bioremediation and provide a foundation for future scale-up and wastewater treatment strategies.