The effect of chloroquine, quinacrine, and metronidazole on both soybean plants and soil microbiota.

Chloroquine, quinacrine, and metronidazole are used extensively for therapeutic purposes. Substantial quantities of these compounds end up in the environment. The potential effect of these compounds on soybean and on the protozoa in soil was assessed. The growth of soybean plants was affected by increasing concentrations of the chloroquine, metronidazole, and quinacrine dihydrochloride. The plants were particularly sensitive to low concentrations of metronidazole. The number of bacteria and protozoa in soil was either unchanged or increased in the presence of chloroquine and quinacrine. However, in the presence of only 0.5 mg metronidazole g(-1) soil, the density of protozoa in the rhizosphere was reduced by a 10-fold.