Quantitative structure-toxicity relationships for halobenzenes in two species of bioluminescent bacteria, Pseudomonas fluorescens and Vibrio fischeri, using an atom-centered semi-empirical molecular-orbital based model

Literature data on the toxicity of substituted benzenes for two bioluminesc ent bacteria, Pseudomonas fluorescens and Vibrio fischeri have been compare d and analysed in relation to a set of computed molecular physico-chemical properties using a quantitative structure-activity approach. The quantitati ve structure-toxicity relationships of the compounds in each species showed marked differences when based upon semi-empirical molecular-orbital whole molecule and atom based properties. Multiple linear regression analysis of P. fluorescens data showed a good co rrelation with HOMO (highest occupied molecular orbital) atom based terms. In contrast, the V. fischeri toxicity data for halobenzenes showed superior correlations with LUMO (lowest unoccupied molecular orbital) atom based te rms. These differences indicate that the toxicology of halobenzenes in the two species may have different molecular mechanisms, thus suggesting cautio us interpretations of such in vitro toxicology data for other chemical clas ses.