Use of Methyl Green in Flow Cytometry to Control the Cell Viability of C. glutamicum

The use of methyl green dye in flow cytometry to monitor the viability of Corynebacterium glutamicum cells was studied. The use of methyl green has an important advantage—its spectra do not overlap with the fluorescence spectra of other fluorophores. Our study demonstrated that the fluorescence spectra of live cells of Corynebacterium do not overlap with the spectra of dead cells stained with methyl green, which is a significant benefit of such use in flow cytometry to monitor the viability of Corynebacterium glutamicum cells. It has been established that the optimal concentration of methyl green for staining C. glutamicum cells is in the range of 5–15 μg/mL. Under these conditions, methyl green is nontoxic to corynebacterial cells, which is confirmed by the coincidence of the titer (number) of living cells determined using flow cytometry or a standard microbiological method based on growth on the nutrient medium.