Potential use of Escherichia coli and Aeromonas hydrophila as bioremediation agents for CuSO4 and ZnCl2 water pollution: insights from AAS and histopathological analysis of Oreochromis mossambicus

This study investigates the potential of Escherichia coli and Aeromonas hydrophila as bioremediation agents for removing copper (Cu) and zinc (Zn) from contaminated water. Although Cu and Zn are necessary in trace levels, excessive amounts can be harmful and can linger in aquatic environments, endangering the food chain. Bioremediation using microorganisms offers an alternative method for mitigating heavy metal pollution. In this study, 126 tilapia fish (Oreochromis mossambicus) were exposed to CuSO4 and ZnCl2 for 15 days, followed by treatment with E. coli and A. hydrophila. Atomic absorption spectrometry (AAS) revealed that both bacterial treatments reduced copper and zinc accumulation in fish organs, though they did not fully heal external lesions. Histopathological analysis showed significant reductions in melanomacrophage centers (MMC), cell necrosis, cell dissociation, and vacuolization in fish liver tissue after bacterial treatment, particularly at concentrations of 2.5 mg.L-1 and 5 mg.L-1 for CuSO4 and 7.5 mg.L-1 for ZnCl2. These findings suggest that E. coli and A. hydrophila have the potential to be developed as effective bioremediation agents for CuSO4 and ZnCl2 pollution in aquatic environments.