Protein Profile Variation in Cultivated and Native Freshwater Microorganisms Exposed to Chemical Environmental Pollutants

Abstract

Assimilation of 35S-precursors into microbial proteins was used to investigate toxicity and adaptational responses that occur in nutrient enriched and natural freshwater samples experimentally contaminated with benzene, toluene, trichloroethylene (TCE), or xylene. Experiments were conducted to analyze (1) the potential of using microbial community protein profiles for responsive identification of chemical pollutant exposure, (2) the inhibition of microbial productivity through reduction in rate of protein synthesis caused by specific chemical pollutants, and (3) whether selection of subpopulations in freshwater microbial communities challenged with chemical pollutants leads to adaptive strategies mediated by production of particular polypeptides. The results show that distinct banding patterns of polypeptides in the range of 30 to 100 kilodaltons that were obtained following collective cultivation of freshwater microorganisms differ with each chemical pollutant. Protein yield and radioisotope incorporation were reduced within ten minutes of micro-bial exposure to chemical pollutants in the following order: xylene < toluene < benzene < TCE. Adaptation of the freshwater microbial community to chemical pollutants prior to radioisotope incorporation produced differences in polypeptide profiles, in the banding patterns of radioactive polypeptides, and in the rate of radioisotope incorporation. The rate of radioisotope incorporation by freshwater microorganisms pre-adapted to chemical pollutants was lowest with xylene (88.1% reduction), followed by TCE (84.0% reduction),toluene (67.3% reduction), and benzene (43.5% reduction). In long-term radioisotope incorporation experiments, protein yield and polypeptide radioactivity was higher in the presence of chemical pollutants than in uncontaminated control samples, suggesting increased metabolic productivity attributable to the chemical pollutants.