Colorimetric Determination of Color of Aerial Mycelium of Streptomycetes

Lyons, Allister J., Jr . (Northern Regional Research Laboratory, Peoria, Ill.)and Thomas G. Pridham . Colorimetric determination of color of aerial mycelium of streptomycetes. J. Bacteriol.89: 159–169. 1965.—For some time, streptomycete taxonomists have been seeking to describe more accurately the colors of aerial mycelium. Some of the descriptive systems involve many different color names and groups. Others combine many colors into a few groups. All the systems and methods leave much to be desired. To obtain an accurate description, a colorimeter with a reflectance attachment was used to examine streptomycete aerial mycelium of 37 strains, representing all of the major aerial mycelium color groups. Each color was characterized by three values: dominant wavelength in millimicrons, and purity and brightness in percentages. All colors of aerial mycelium were of low purity (< 25%). Most of the dominant wavelengths were in the yellow to yellow-green bands of the spectrum. Most of the color tabs matched visually with the streptomycete strains had purities of a higher value than those of the cultures. The reflectance instrument seems to allow an objective description, and its use may help to clarify the color problem with streptomycetes. It is concluded that present color descriptions are inadequate and that the significance of color in speciation requires critical examination.