Modeling the toxicity of polar and nonpolar narcotic compounds to luminescent bacterium Shk1.

Luminescent bacterium Shk1 was created for the purpose of testing and screening the toxicity of activated sludge wastewater treatment plant influent to avoid toxic shock to the wastewater treatment plant microorganisms. The toxicity of a number of organic compounds was tested using an assay employing Shk1. Because these compounds exhibit toxicity by mechanisms of both polar and nonpolar narcosis, their toxicity cannot be properly modeled together using a quantitative structure-activity relationship model based on the logarithm of the octanol-water partition coefficient (log K(ow)). A solvation parameter model was developed to describe and predict the nonspecific (i.e., polar and nonpolar narcosis) toxicity of organic compounds to Shk1, which does not depend on the discrimination between polar and nonpolar narcotic compounds. The statistically significant model descriptors were the McGowan's characteristic volume (V(x)) and the hydrogen-bond basicity (sigmabetaH). The model was similar to the solvation parameter model developed for Vibrio fischeri, but it did not include an excess molar refraction (R) term.