Kepone Toxicity to Estuarine Microorganisms

Abstract

Synthesized chemical agents can have an unseen, and yet profound, impact on the environment in which it is used. This study investigates the effects of the insecticide Kepone (99% pure) on estuarine microbial populations and seeks to determine the mode of toxicity to pure culture isolates obtained therein. The researcher used disc agar diffusion sensitivity, plate counts, and oxygen uptake methods to collect data over a period of four months to determine the toxicity of Kepone to a variety of laboratory pure cultures of bacteria and fungi. Of the 30 isolates tested, 33% were inhibited at 3.65 ?g/disc concentration and 47% were inhibited at the 14.6 ?g/disc concentration. Higher concentrations (20 ?g/disc) inhibited all isolates. Of the 30 isolates, seven were particularly sensitive to Kepone, with four indicating inhibition at the 1.46 ?g/disc concentration. The researcher then examined the toxicity of Kepone to natural mixed populations of bacteria from a variety of marine habitats by performing standard total viable counts using Zobell’s seawater agar (Z-15) containing dissolved Kepone. The researcher observed that Kepone as low as 20 ?g/l has an inhibitory effect on the development of colonies on an agar plate, though the populations’ sensitivities were variable. In many cases, it was clear that concentrations below 20 ?g/l were inhibitory. Seventeen Kepone-resistant colony forming units were selected for further study, however, examination of cell type and enzymatic activities showed significant correlation only with the amylolytic and lipolytic activities, and the gram stain. The researcher observed that organisms grown under anaerobic conditions exhibited decreased sensitivity to Kepone, however, significant reductions in colony forming units were observed under aerobic conditions. The researcher concludes that Kepone is toxic to microorganisms even in low concentrations.