Agar-Decomposing Strains of the Actinomyces Coelicolor Species-Group.

The ability to decompose agar has not hitherto been recorded for any member of the Actinomycetales, and consequently it seemed desirable to make a detailed study of a typical Actinomyces possessing this property, which was discovered fortuitously. The organism appeared on a discarded tapwater agar plate (used originally for the germination of myxomycete sclerotia) in the form of blue-black colonies with scanty greyish-white aerial mycelium, each of which lay in the center of a marked depression in the agar. Several strains were isolated and purified by repeated streaking on mineral agar plates with (NH4)2SO4 as a nitrogen source. The behavior of the pigment produced (blue under basic, red under acid conditions) marked the organism at once as a member of the widespread soil group of litmus actinomycetes, which are classified in Bergey's Manual under the name A. coelicolor. In response to my request, Dr. S. A. Waksman very kindly provided me with an authentic culture of this species from his collection, together with several agar-decomposing strains which had been isolated at the New Jersey Agricultural Experiment Station in the course of other work. These cultures (NB strains) together with my own isolates (PG strains) comprised the material for the following studies.