Method of correction when determining cell concentrations by the plating technique

Abstract

One of the methods of determining cell concentrations in solutions is to apply a suitably diluted cell suspension to agar plates and count the resultant colonies. For this method to be correct it must be assumed tha t one colony grows from every living cell. In addition to single cells, however, a bacterial culture contains a considerable number of cells in pairs, chains and large groups, which, when transferred to agar, also give rise to only one colony (St~rka, 1959). These pseudomycelia do not divide into individual cells even after multiple progressive dilution of the culture. Our experiments showed tha t when we diluted a culture to 10 -4 of the original cell concentration, the numbers of pairs of cells, expressed as a percentage of the total count, varied by maximally + 5 % . This means tha t all measurements based on the above method are loaded with a standard error producing lower results than the actual cell concentration in the solution (determined, for example, by counting the cells directly in a counting chamber). The aim of the present s tudy was to correct these results so as to eliminate, or at least modify, the error of such measurements. Our method is based on the premises submitted below. We denote the number of pseudomycelia in a medium volume unit as m and assume tha t each of them is composed of s cells. I f the cell concentration determined by a colony count on agar is denoted as n, then assuming tha t every individual cell and every pseudomycelium gives rise to one colony, the actual number of cells in the given volume unit will be determined by the relationship

DOI: 10.1007/BF02872802

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Cite this paper

@article{Mka1969MethodOC, title={Method of correction when determining cell concentrations by the plating technique}, author={Viliam M{\'u}{\vc}ka and J. Cabicar}, journal={Folia Microbiologica}, year={1969}, volume={14}, pages={511-514} }