title: Suitability of the modified fluctuation assay for evaluating the mutagenicity of unconcentrated drinking water.
abstract: Filter-sterilized, unconcentrated tap water induced mutagenic responses (p less than 0.01) in Salmonella strain TA100 in fluctuation assays, usually with dose-related increases in positive tubes. Additional experiments were performed to study possible artifacts that could lead to falsely positive results. Determinations of bacterial survival revealed that cell populations in the tubes containing tap water were larger than in the controls. Since spontaneous mutation is a function of cell generation, the increased numbers of bacteria appeared to be responsible for the higher numbers of mutants observed. Therefore, the positive responses must be regarded as artifactual. This study suggests that survival determination should be a routine part of this method, and care should be exercised in the interpretation of positive results.
mesh_terms: D002455:Cell Division; D005189:False Positive Reactions; D008722:Methods; D009152:Mutagenicity Tests; D009153:Mutagens / Q000633:toxicity*; D009154:Mutation; D012486:Salmonella typhimurium / Q000235:genetics; D014881:Water Supply / Q000592:standards*
chemical_list: D009153:Mutagens