One-step fluorometric microassay of DNA in procaryotes.

A fluorometric DNA microassay in procaryotes is proposed. The fluorescent dye employed is 4',6-diamidino-2-phenylindole X 2HCl, which exhibits very high specificity for DNA. The assay can be directly made on whole bacteria without DNA purification. Bacteria are treated with toluene and the fluorescent dye is added. The range of linearity has been explored. The stability, reproducibility, and accuracy of fluorescence measurements permit one to determine the equivalent number of genomes per cell and to distinguish between two different but very similar modes of increase in DNA quantity: bilinear or exponential synthesis.