Assessment of Metals Toxicity Using a Nitrifying Bacteria Bioassay Kit Based on Oxygen Consumption.

The escalating concentrations of emerging contaminants in water systems and the possible environmental threats they emphasize the necessity for more sophisticated methods in the evaluation of water quality. Traditional bioassays raise ethical concerns, require intricate procedures, entail significant expenses, and only allow for endpoint measurements. The using of nitrifying bacteria in bioassays has resulted in increased sensitivity to a wide range of toxic substances, making them valuable for the identification of water pollution. This study introduces a novel nitrifying bacteria bioassay kit for detecting heavy metal contaminants in water. This bioassay is specifically designed for expedited analysis of oxygen consumption. This technique enables the identification of a range of toxic metals. Optimization studies indicated that 100 mg ammonia NH₄⁺-N/L, and 1 mL acclimated culture were the ideal conditions facilitating the necessary volume of gas consumption for sensitive data generation. Determined EC₅₀ values of the selected toxic metals were: chromium (Cr⁶⁺), 0.51 mg/L; silver (Ag⁺), 2.90 mg/L; copper (Cu²⁺), 2.90 mg/L; nickel (Ni²⁺), 3.60 mg/L; arsenic (As³⁺), 4.10 mg/L; cadmium (Cd²⁺), 5.56 mg/L; mercury (Hg²⁺), 8.06 mg/L; and lead (Pb²⁺), 19.3 mg/L. Metagenomics analysis found key species in the research included Nitrosomonas eutropha, Nitrosomonas oligotropha, Nitrosomonas europaea, Nitrobacter vulgaris, Nitrobacter winogradskyi, Nitrospira moscoviensis and Nitrospira lenta. In addition, this bioassay is ideal for field screening and real-time monitoring due to its simplicity and reliability. This bioassay provides a precise, economical, and effective substitute for more intricate and ethically problematic techniques, enhancing the effectiveness of water quality monitoring programs.