Enhancement of Heavy Metal Reduction by UV- -Induced Mutants of Pseudomonas putida

AbstractHeavy-metal contamination of freshwater ecosystems poses severe ecological and human healthrisks, necessitating cost-effective and sustainable remediation strategies. In this study, bacterialisolates from six ecologically distinct sites along the Hindon River (Saharanpur district, India)were investigated for their potential to remediate copper (Cu2+) and nickel (Ni2+) contamination.Enumeration and isolation on nutrient agar yielded multiple bacterial strains, of which two wereidentified through biochemical characterization as Pseudomonas putida (H101) and Bacillussubtilis (H102). Heavy-metal tolerance assays revealed significant resistance of H101 to Cu2+and Ni2+, prompting UV mutagenesis to enhance its remediation efficiency. Mutant derivativesdemonstrated improved performance, achieving Cu2+ reduction of 35.00 ± 2.40% and Ni2+reduction of 47.00 ± 2.10%, compared to 21.00 ± 2.10% and 23.00 ± 1.90% in the wild type.Optimization studies showed that temperature (37 °C), pH (6.0), carbon source (sucrose for Ni2+,yielding 58.00 ± 1.60%), and nitrogen source (peptone, supporting 26.00 ± 1.80% Ni2+reduction) significantly influenced bioreduction efficiency (p < 0.05). Consortium culture ofH101 with H102 exhibited enhanced growth kinetics (OD600 = 1.50) compared to monocultures(OD600 = 1.30–1.38), indicating synergistic interactions that strengthened resilience under metalstress. Antibiotic susceptibility profiling revealed multidrug resistance traits, including resistanceto ampicillin and vancomycin but susceptibility to ciprofloxacin, tetracycline, and gentamicin,underscoring the dual ecological significance of the strain.These findings establish UV-mutated P. putida H101 as a robust candidate for Cu2+ and Ni2+bioremediation, with optimized conditions and consortium-based strategies offering enhancedHigh Technology Letters performance. The study provides mechanistic insights into bacterial metal reduction andhighlights the promise of microbial approaches for mitigating industrial and agriculturalpollution in riverine ecosystems.