Effects of microbial community interactions on transformation rates of xenobiotic chemicals.

The effects of culture filtrates, mixed populations, and common microbial exudates on bacterial transformations of three agricultural and industrial chemicals were investigated. Test chemicals included methyl parathion, diethyl phthalate, and 2,4-dichlorophenoxyacetic acid butoxyethyl ester. The presence of various cultures, filtrates, or exudates of algae, fungi, or other bacteria either stimulated or inhibited bacterial transformation rates. Inhibition resulted from treatments that lowered the pH, and stimulation resulted from an increase in cell biomass (based on plate counts) and from a different process whereby rates of transformation per bacterial cell rapidly increased as much as 10-fold.