Toxicity assay of heavy metals Pb, Cd and Cu by luminescent bacterium isolated from the Caspian Sea

Due to widespread environmental pollution contaminants and heavy metals, using of modern, fast and high performance methods for detection of contaminants has great significance. One of the methods to assay the toxicity of environmental samples is use of luminescent bacteria for toxicity assay based on bioluminescence inhibition. The purpose of current study was toxicity assay of heavy metals using luminescent bacterium isolated from the Caspian Sea. Water samples were collected from different depth of the Caspian Sea. For isolation of luminescent bacteria, samples were inoculated into specific medium and incubated at 28 °C. Growth and luminescence of isolate were studied using spectrophotometry and luminometry. Then assessment of toxicity of heavy metals including Pb, Cd and Cu was performed using luminescence property of the isolate. Of the sea water a luminescent bacterium was isolated named MM1. The result of bioluminescence investigation revealed that the isolate MM1 can be able to emit steady and high level of light. The light emission of isolate MM1 was significantly decreased in the presence of heavy metals. The results revealed that the isolate was able to detect low concentration of heavy metals. The EC50 values for Pb, Cd and Cu were assayed 8.55, 18.46 and 3.77 mgL-1, respectively. The results of this study demonstrated that luminescence activity of bacterium isolated from the Caspian Sea was sensitive to the presence of heavy metals and was significantly reduced. The isolate can be used for toxicity assay of environmental pollutants especially for heavy metals.