Vibrio fischeri
About Vibrio Fischeri
The use of living organisms is the only way to reliably measure the toxicity of a water or soil sample. Microtox® utilizes vibrio fischeri as the organism of choice for rapid toxicity testing. Vibrio fischeri are nonpathogenic, marine, luminescent bacteria which are sensitive to a wide range of toxicants. The organisms are supplied for use in a standard freeze-dried (lyophilized) state, which serves to maintain the sensitivity and stability of the test organisms. Disruption of the respiratory process, by exposure to a toxicant affects the metabolic pathway that converts chemical energy via the electron transfer system of the bacteria to visible light. The process occurs in and close to the cell membrane so target sites are close to the cell surface.
Each test uses approximately 1 million organisms and each organism is less than 1 mm in diameter, so a very high surface-to-volume ratio is presented. Sensitivity and statistical significance are, therefore, high; the response being an integrated effect of the toxicant on the entire population, which is very large.
Toxicity and Vibrio Fischeri
The effective concentration (EC50) is determined as the concentration of a toxicant that causes a 50% reduction in light output over a prescribed period of time (typically 5, 15, or 30 min). The test is fast, simple to conduct, uses small sample sizes, and is very cost effective. Results correlate well with those from other toxicity bioassays such as finfish, Daphnia and mysid shrimp. The test is used extensively in the measurement of toxicity of wastewater treatment effluent and influent, water for human consumption and use, as well as a myriad of other applications where it is important to know the level of toxicity and contamination in a water sample.