A TRIAL TO COMPARE THE EFFECTS OF PH, BUFFER CONCENTRATION, AND NACL,ON ONE FLUORESCENT AND 2 BIOLUMINESCENT BACTERIAL TESTS FOR ACUTE TOXICITY

Of all the bioassays to determine acute toxicity described in the lite rature, Those that employ bacteria as indicator organisms are usually the most rapid and the most economic, although alone they cannot predi ct the possible toxic effect of any type of substance. When bioassays are employed to test the toxicity of known substances and of compounds in samples from waste discharges they have to work in very different conditions from those for which they were designed. The effects of thr ee factors, pH, buffer concentration, and NaCl, on the performance of a fluorogenic bioassay based on the beta-glucuronidase activity of Esc herichia coli were investigated. The results of this test were compare d with those of two known biluminescent bacterial tests. The fluorogen ic bioassay has a more restricted optimun pH range, while the influenc e of buffer concentration was similar for the three tests. E. coli glu curonidase activity was affected at a concentration as low as 128 mg/l of NaCl. Changes in the pH or buffer concentrations or chloride ions, greatly influenced the respectives toxicities of four substances, acr idine orange, TEMED, 2-mercaptoethanol, and mercuric chloride.