Synergistic and Hermetic Effects of Volatile Organic Compounds on Marine Luminescent Bacterium Vibrio fischeri

摘要

Various chemical contaminants present including unknown and unidentified pollutants in indoor environment. These toxicities as mixture have not been evaluated with any regard for the possibility of serious impacts on the environment. This study aimed to find the influence on bioluminescence of luminescent bacterium Vibrio fishceri, when typical indoor air pollutants (VOCs) were mixed, compared with the case of single components. Bioassay using V. fischeri is well known as a novel screening method for toxicity evaluation of the environmental contamination. Both single and mixed VOC solutions by two kinds of VOCs were prepared in various concentration levels with dilution by methanol as a solvent. Acetaldehyde, formaldehyde, toluene and ethyl benzene were tested as typical VOCs. Each sample solution (50 μL) was mixed into 2 ml of reactivated bacterial solution in a well of 24-well plate. Then, time course of relative bioluminescence intensity (BLI) was measured by a luminometer with blank and positive control solution. Then, EC50 of single components were obtained from dose-response curves and mixed toxic properties were evaluated with mixture toxicity index, MTI. As a result, every mixture showed significant increasing or decreasing of toxicity compared with the cases of single VOCs probably because of synergistic effect. On the other hand, biostimulation was observed in the low concentration ranges of each VOC, even these components remarkably inhibited the bioluminescence at high concentrations. This result probably indicates the hermetic effect for VOCs. This study suggests that some combinations of VOCs have more serious or trivial impacts on marine luminescent bacterium than previously recognized.