Characterization of nitrifying bacteria and exploring a novel approach for toxicity monitoring in water

A novel methodology has been developed to detect toxicity by harnessing the capabilities of nitrifying bacteria, ensuring the accurate identification of harmful chemicals in water. This innovative method leverages the inherent ability of bacteria to convert ammonia into nitrite and nitrate through oxidation, as demonstrated by the chemical reactions: 2 NH 4 + + 3 O 2 → 2 NO 2 − + 2 H 2 O + 4H + and 2 NO 2 − + O 2 → 2 NO 3 − . Increased oxygen consumption and reduced pH levels are outcomes of the oxidation process, which are essential parameters in our evaluation of nitrifying bacteria toxicity using the test kit. The validation of the methodology was confirmed by conducting accurate measurements of oxygen consumption and pH fluctuations. Upon exposure to an experimental setting with a concentration of 100 mg/L of ammonia, it was noted that the oxygen consumption rate was around 3.2 mL. The presence of hexavalent chromium (Cr 6+ ) and other metals have been shown to impede the process of nitrification, leading to lower oxygen consumption and a subsequent drop in pH levels. Ammonia-oxidizing bacteria (AOB) and Nitrite-oxidizing bacteria (NOB) were effectively isolated from a nitrifying bacteria master culture reactor. The metagenomics analysis indicated that the major isolated strains possess a sequence similarity of 99 % and 100 % with Nitrosomonas europaea and Nitrobacter winogradskyi , respectively. With its high sensitivity and cost-effectiveness, our nitrifying bacteria test kit is well-suited for the monitoring of toxic chemicals in water, making it an ideal tool for this purpose. This bioassay testing kit represents a notable progression in environmental protection, offering a strong and effective method for promptly identifying water pollutants. • An early warning system for water quality has been created to assess the presence of acute water toxicity. • The potential for innovative bioassays to monitor water quality is emphasized. • Exposure to excess concentration of pollutants induces inhibition of microbial growth of nitrifying bacteria. • The effect of a novel bioassay kit on the toxicity of different metals is discussed.