[Vital fluorescent staining of microorganisms by 3',6'-diacetyl-fluoresceine for determination of their metabolic activity (author's transl)].

By fluorescent microscopy and spectroscopy studies involving micro-organisms which were either viable or devitalised by heat sterilisation or gamma irradiation and could not be cultured any more, fluorochrome binding with 3' , 6'-diacetyl fluorescein was shown to be linked with the viability of a cell and a function of its actual metabolic state. The incorporation of diacetyl fluorescein into cells, its storage and hydrolysis to fluorescein mean active processes taking place at high speed. Viable cells are capable of storing fluorescein intracellularly, bound to structural elements. If the storage capacity is surpassed, it will be eliminated from the cell. The mechanism of this process is discussed. Devitalised cells are not capable of active uptake of fluorescein nor of its storage and accelerated hydrolysis. Beyond this, they are incapable of fluorescein binding to structural elements. There will be only a minor homogenous staining of such cells by fluorescein. An express method based upon the results is providing information on viability, actual metabolic state, morphology, and motility of micro-organisms within a few minutes and without affecting onward culturing.