SIMPLE PHOTOMETRIC AND FLUOROMETRIC ASSAYS ARE INSUFFICIENT FOR ASSESSING UV-INDUCED
MUTAGENESIS IN GENE CONTROLLING TRYPTOPHAN SYNTHESIS IN ESCHERICHIA COLI CELLS
S. V. Zherebtsov
Institute of Cytology RAS, St. Petersburg
A new approach to detecting induced mutations was tested based on the assay of cell extracts and special growth
media following cultivation of UV irradiated Escherichia ñîli cells. No correlation was found between the UV
dose and the optical densities of cultural media or cell extracts prepared by Triton X-100 treatment. Blue
fluorescence of concentrated cultural media varied with cell dose, according to a rather complex law, which
differed substantially from the known dose-effect curves for induced mutions. Nevertheless, a certain extent of the
brown staining of tryptophan containing medium could, presumably, serve as a quite sensitive indicator of the
integral metabolic activity of bacteria grown in the medium. Besides, we observed that overnight lag phase cultures
became gradually more transparent, when analysed in the spectrophotometer cuvette just after their dilution with
fresh medium.
Key words: mutagenesis, fluorescence, photometry, Escherichia coli
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