Microbial Removal of Heavy Metals Using Endogenous Metal-Resistant Strains: A Case Study of Zarjub River, Rasht
محورهای موضوعی : Biotechnological Journal of Environmental Microorganisms
1 - Department of Microbiology, Faculty of Basic Sciences, Islamic Azad University, Rasht Branch
کلید واژه: Heavy metal resistance, bioremediation, Pseudomonas, Zarjub River, microbial adaptation, pollution gradient, biosorption.,
چکیده مقاله :
Surface water pollution caused by heavy metals is one of the significant environmental challenges of our time, with far-reaching consequences for aquatic ecosystems and human health. Metals such as chromium (Cr), cadmium (Cd), and arsenic (As) present a serious threat due to their high toxicity, environmental persistence, and potential for bioaccumulation, even at low concentrations. This study investigated the heavy metal resistance and bioremediation potential of indigenous bacterial strains isolated from the Zarjub River in Rasht, a freshwater ecosystem affected by agricultural, urban, and industrial pollution. Systematic sampling revealed elevated concentrations of Cr (VI) (up to 102.4 μg/L), Cd (II) (28.6 μg/L), and As (III) (47.3 μg/L) downstream, correlating with anthropogenic inputs. Among the 18 characterized strains, Pseudomonas spp. (ZR-07, ZR-10) demonstrated exceptional multi-metal resistance, tolerating 500 mg/L Cr (VI), 200 mg/L Cd (II), and 300 mg/L As (III), while Bacillus strains (ZR-06, ZR-14) exhibited moderate but stable resistance. Biosorption assays indicated a metal removal efficiency of 60–88%, with Pseudomonas strains outperforming others due to enhanced production of extracellular polymeric substances. These findings highlight the ecological selection pressure imposed by pollution and the potential of native strains for bioremediation applications. However, the co-occurrence of metal resistance with virulence traits in some strains underscores the need for careful risk assessment.
Surface water pollution caused by heavy metals is one of the significant environmental challenges of our time, with far-reaching consequences for aquatic ecosystems and human health. Metals such as chromium (Cr), cadmium (Cd), and arsenic (As) present a serious threat due to their high toxicity, environmental persistence, and potential for bioaccumulation, even at low concentrations. This study investigated the heavy metal resistance and bioremediation potential of indigenous bacterial strains isolated from the Zarjub River in Rasht, a freshwater ecosystem affected by agricultural, urban, and industrial pollution. Systematic sampling revealed elevated concentrations of Cr (VI) (up to 102.4 μg/L), Cd (II) (28.6 μg/L), and As (III) (47.3 μg/L) downstream, correlating with anthropogenic inputs. Among the 18 characterized strains, Pseudomonas spp. (ZR-07, ZR-10) demonstrated exceptional multi-metal resistance, tolerating 500 mg/L Cr (VI), 200 mg/L Cd (II), and 300 mg/L As (III), while Bacillus strains (ZR-06, ZR-14) exhibited moderate but stable resistance. Biosorption assays indicated a metal removal efficiency of 60–88%, with Pseudomonas strains outperforming others due to enhanced production of extracellular polymeric substances. These findings highlight the ecological selection pressure imposed by pollution and the potential of native strains for bioremediation applications. However, the co-occurrence of metal resistance with virulence traits in some strains underscores the need for careful risk assessment.
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