Value of Pigmentation in Classifying Actinomycetes

Abstract

The colors produced by species of Actino-myces, although striking, show such variability that they cannot be used successfully in classification. Apparently, however, pigment production is fairly constant for any strain. The variability in color is due to the fact that these pigments act as H-ion indicators, and that the appearance of any culture may vary greatly according to whether the pigment is present in its alkaline or acid phase or partly in each form. As the final pH of such an organism on synthetic media is variable, accordingly the color varies. There is good evidence that if instead of recording the color of a culture, one makes a few simple tests as to its solubility in certain reagents and the color assumed by its solutions at differing pH-values, one can use pigmentation as a feature sufficiently constant to be of diagnostic value.