DETECTION OF DNA-DAMAGES IN AQUATIC PROTO ZOA AND ALGAE BY MEANS OF MICROGEL ELECTROPHORESIS (COMET ASSAY) FOR GENOTOXICOLOGICAL QUALITY MAPPING OF SURFACE-WATER

The assessment of genotoxicity in surface water requires sensitive met hods which are able to detect DNA-damage in organisms of the aquatic b iocenosis. The microgel electrophoresis (MGE), the so-called comet ass ay, is a sensitive technique to detect strand breaks and alkaline-labi le sites in the DNA of eucaryotic organisms or cells. Results of the a pplication of the MGE to a unicellular green alga (Chlamydomonas reinh ardtii) and to an ubiquitous protozoa (Acanthamoeba castellanii) were shown. Short-time exposure to well-known genotoxicants, e.g., 4-nitroq uinoline1-oxide (4-NQO), benzo(a)pyrene etc., are used for the validat ion of the new methods and led to dose-dependent DNA-damage. Moreover, a survey of a native surface water sample spiked with various concent rations of an EPA standard mixture were presented. The two organisms s how different sensitivities to the distinct genotoxicants as expected. Chlamydomonas reinhardtii and Acanthamoeba castellanii responded very sensitively to treatment with increasing doses of 4-NQO. At concentra tions of 1 mu g/L to 10 mu g/L 4-NQO, significant DNA-damage was obser ved.