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Optimization of Bioluminescence of Vibrio fischeri and Assessment of Hg++, Cd++, As++, Zn++, Ag+, Cu++ and Ni++ Ions
Various forms of metallic elements are ubiquitous in the environment. The presence of heavy metals in the environment results from natural causes and human activities. They are necessary and even essential for growth and well-being of living organisms. Meanwhile, at high concentration they pose a particular problem by exhibiting more or less strong toxicity. Unlike other toxicants, these elements are not biodegradable. Therefore, they accumulate by marine organisms throughout food chain, which represent a potential danger for flora and fauna. Their toxicity on organisms and their impact on the environment were very different. One of the most important part to evaluate environmental pollution is assessment of heavy metals. Therefore, it is important to use a simple and cost effective method to evaluate toxicants. In this regard, a bioluminescence inhibition method has been optimized. This method consisted to optimize the intensity and stability of luminescence emitted by bacteria Vibrio fischeri (V. fischeri) strain NRRL-B-11177. Toxic effects of Cd++, Zn++, As++, Ag+, Ni++, Cu++ and Hg++ ions have been determined using the method. Results showed aeration (900 ml/min) and agitation (250 rpm) were essential to V. fischeri to emit light. Hg++ ion was the most toxic compared to other tested ions with EC50 value of 0.008 ± 0.001 mg/l. Thus, this method is simple, rapid, sensitive and cost effective, could be used to assess a considerable amount of samples.