Abstract:

After complete disruption of the microbial cell wall with thymol, the nucleic acids or DNAs were labeled with
propidium iodide for the detection of fluorescence values. A standard curve was established for extrapolating total number
of colonies based on the fluorescence values. The results showed that the optimal thymol concentration for breaking the
microbial cell wall was 4 mmol/L. The relative standard deviation of this method for the determination of the fluorescence of
B. subtilis colonies was 1.29%, and the recovery rate was 98.4%. This method is accurate, reliable, simple and rapid without
the use of a large amount of plates.

Key words: fluorescence labeling, the total number of colonies, thymol