Quantitative adsorption of crystal violet.

The formula for crystal violet given in Conn's book (1940) implies that quantitative measurement of the dye adsorbed by bacterial cells should be possible by a suitable micro-Kjeldahl procedure. At the present time there is no satisfactory method for estimating the degree of gram positivity although the need for such a procedure is recognized and is discussed by Bartholomew and Mittwer (1952). It is considered that the procedures reported here provide a useful tool for further quantitative studies on the gram reaction. The present report shows that the amount of crystal violet combined with bacteria can be measured accurately by means of a simple microKjeldahl procedure widely used in immunochemistry. The experiments reported were designed to determine the effect of the sjpecies and strain of the organism used, of the method of killing the cells, and of the time of contact with the dye, on the quantitative adsorption of crystal violet.