<![CDATA[Abstract. Kristina IG, Irawati W, Dikson, Pinontoan R. 2026. Genomic characterization of Escherichia coli Cn5 and IrN exhibiting copper resistance and malachite green decolorization. Biodiversitas 27 (6): d270623. https://doi.org/10.13057/biodiv/d270623. Copper and textile dye pollution pose significant environmental threats because of their adverse effects on aquatic ecosystems and human health. Bioremediation using indigenous bacteria has emerged as an effective, eco-friendly, and cost-efficient alternative to conventional treatments. However, genomic studies on bacteria exhibiting both heavy-metal resistance and dye decolorization remain limited. This study served as a preliminary evaluation of indigenous bacterial isolates from Indonesia for their copper (Cu) resistance and Malachite Green (MG) decolorization phenotypes and genotypes. Phenotype assessment involved their growth and activity on liquid and solid Luria-Bertani media supplemented with increasing concentrations of CuSO4 or MG. Genotype assessment involved Nanopore whole-genome sequencing and annotation to determine taxonomic identity and putative functional genes. Two isolates, Cn5 and IrN, tolerated up to 12 mM CuSO₄ and 20 ppm MG dye. The MG decolorization assays revealed efficiencies of 90.8% for isolate Cn5 and 93.4% for isolate IrN after 4 days of incubation, indicating bioremediation potential. Whole-genome comparison, multilocus sequence typing, and phylogenetic analysis confirmed that both isolates belong to Escherichia coli. Comparative genomics identified gene clusters putatively associated with Cu resistance, including cop, cue, and cus genes. Functional annotation revealed four reductase genes, one peroxidase gene, and one laccase-encoding gene potentially involved in MG dye decolorization. This study provides a preliminary genomic characterization of E. coli strains combining Cu resistance and MG decolorization as a baseline for further investigation of their bioremediation-related potential.]]>
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