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Response of Vibrio fischeri to repeated exposures over time in an Online Toxicity Monitor
Citation:
Allen, Joel, N. Muhamad, D. Macke, AND S. Panguluri. Response of Vibrio fischeri to repeated exposures over time in an Online Toxicity Monitor. Presented at Society of Environmental Toxicology and Chemistry, Long Beach, CA, November 11 - 15, 2012.
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Description:
Online Toxicity Monitors have been developed to provide continuous, time-relevant information regarding water quality. These systems measure a physiological or behavioral response of a sentinel organism to changes water quality. One such system, the Microlan Toxcontrol, is based on the Vibrio fischeri model. Changes in luminescence of these bacteria over the course of a brief exposure period are an indication of the influence of water quality on the overall well-being of the organisms. This system is an autonomous, discrete exposure system which is intended to operate for a period of seven days with the same batch of bacteria. Research presented here was designed to look at the sensitivity of V. fischeri over time. The V. fischeri assay requires an isotonic diluent prepared with 2% sodium chloride. An addition of 3ppm sodium thiosulfate was added to remove chlorine in chlorinated drinking water applications. Luminescence of control and treatment bacteria were measured simultaneously and used to compute percent inhibition. Two experiments will be presented. The first is a series of 24 hour exposures comparing control water to additions of 3ppm sodium thiosulfate, 3ppm sodium thiosulfate and 1ppm Chlorine residual, and 3ppm sodium thiosulfate and 3ppm Chlorine residual. Results demonstrated that responses to control water and 3ppm sodium thiosulfate were equivalent and consistent over the 24 hour period. Exposure to 1ppm chlorine residual resulted in increased variation and positive response relative to the control. Variability was linearly linked to the actual chlorine residual. Exposure to 3ppm chlorine residual resulted in a consistent negative response as was expected. The second experiment was a seven day test with daily exposure to 10ppm copper. Results indicate that luminescence decreased over the seven day period in an exponential manner. Sensitivity of the bacteria batch increased over the duration of the experiment following a similar patter
