. The actinomycetes. Actinomycetales. 36 THE ACTINOMYCETES, Vol. I with special antibiotic-producing properties. Their excessive growth is no doubt due to the introduction of a fresh supply of avail- able nutrients in the form of bacterial cells. An examination of soils enriched with streptomyces spores, using the Rossi-Cho- lodny contact slide method, revealed that those spores remained in the soil largely in an ungerminated state. They grew only on the rim of the soil adhering to the glass and in the dead bodies of soil amoebae (Pfennig). Nature of the soil actinomycete population. No attemp
. The actinomycetes. Actinomycetales. 36 THE ACTINOMYCETES, Vol. I with special antibiotic-producing properties. Their excessive growth is no doubt due to the introduction of a fresh supply of avail- able nutrients in the form of bacterial cells. An examination of soils enriched with streptomyces spores, using the Rossi-Cho- lodny contact slide method, revealed that those spores remained in the soil largely in an ungerminated state. They grew only on the rim of the soil adhering to the glass and in the dead bodies of soil amoebae (Pfennig). Nature of the soil actinomycete population. No attempt will be made to review here in detail the numerous other investigations on the abundance of actinomycetes in the soil, as determined by the plate method. Suffice to say that all these studies established the fact that actinomycetes form an essential constituent part of the soil microbiological 200- < O Od LJ Q. (/) z o population. Although some assumptions have been made that colony counts of bac- teria, actinomycetes, and fungi represent the numbers of spores in the soil and not of ac- tive organisms, the evidence presented here proves the contrary. By separating the no- cardias (designated as proactinomycetes) from the streptomyces (designated as actino- mycetes). Topping failed completely to rec- ognize the nature of these organisms, namely, their vegetative versus sporulating growth, and the possible confusion between them; he did recognize, however, the nocar- dias and nocardia-like organisms as members of the native or ''autochthonous" microflora of the soil. Further information on the occur- rence of nocardias in the soil is found in the work of Frey and Hagan (1931) and Gordon and Hagan (1937). 150 -. 100 - INCUBATION- DAYS Figure 19. Comi)aris()ii bctwccii donsity of vegetative inyeolium and ])late counts of actinomycetes in soil. Continuous line: density of myceliiun; l)rok(>n line: platecounts (Reproduced from: Jensen, H. L. I'roc. Linnean Soc. N. S. Wal
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