34 



THE ACTIXOMYCETES, Vol. I 



organism was observed, peak counts corre- 

 sponding to the rod form and troughs to the 

 mycehal form, and the steadying in count 

 to the rod form. 



Numerous attempts have l^een made to 

 classify streptomycetes by their growth 

 characteristics on agar media in which a soil 

 has been plated out. Misiek (1949) found 

 that variability and inconsistency in diffu- 

 sible pigment production and carbon utiliza- 

 tion rendered their use for identification pur- 

 poses unfeasible. Of the various properties 

 considered, pigmentation patterns of vegeta- 

 tive mycelium, and the appearance of aerial 

 hyphae and spores were less variable, and 

 thus more conducive to a study of this na- 

 ture. An examination of 1,510 isolates for 

 their carbon utilization gave positive results 

 that varied from 5 per cent for sorbitol to 

 98 per cent for glycerol, with inulin, sucrose, 

 arabinose, rhamnose, rafhnose, xylose, man- 

 nitol, lactose, cellobiose, levulose, starch, 

 dextrin, galactose, maltose, and glucose in 

 increasing order. 



The streptomyces isolated from soil at 

 depths of 8 and 16 inches were the same as 



Table 6 



Distribution of actinoniycctes in tivo forest soils 

 during different seasons of year (Cobb) 



Counts of organisms repre.sent numbers 

 per gram dry soil 



* Soil frozen. 



those found near the surface, and were prob- 

 ably transported downward by the percola- 

 tion of surface water. The presence of large 

 numbers of a particular variety in a soil gave 

 a definite indication of its predominance. A 

 significant correlation was believed to exist 

 between different soil samples within a soil 

 series and between similar series, and some 

 types of predominating streptomyces popu- 

 lations inhabiting these soils. No correlation 

 could be made between topsoil reaction, soil 

 series, and predominating varieties of strep- 

 tomyces cultures. Certain predominating 

 varieties in a given soil were found to ap- 

 pear, disappear, and reappear during certain 

 periods of the year, a phenomenon more ap- 

 parent in some soils than in others. 



Numerous other studies were made of the 

 total abundance and occurrence of specific 

 types of actinomycetes, especially strepto- 

 myces, in different parts of the world. They 

 were reported in great abundance from soils 

 as far apart as the United States (Starkey, 

 Vandecaveye et al., Cobb), China (Eggle- 

 ton), Formosa (Adachi), Japan, South Amer- 

 ica, and India. Their great abundance in 

 peat soils (Zimenka) must be clearly differ- 

 entiated from their occurrence in peat bogs. 

 They are largely limited to the very top 

 layer of lowmoor peat bogs, and are absent 

 entirely from natural highmoor peats ; in the 

 latter, both the combined acidity and mois- 

 ture saturation are the factors responsible 

 for their absence (Waksman and Purvis). 



JMijcelial versus spore stages. The c}uestion 

 of whether actinomycetes occur in the soil 

 in the mycelial or the spore stage has been 

 given considerable attention. Conn was the 

 first to demonstrate, by the direct staining 

 method, that actinomycetes occur in the soil 

 as vegetative mycelium. Subrahmanyan, on 

 the other hand, found that actinomj^cetes 

 occur in the soil largely as spores; vegetative 

 mycelium was said to be present on unde- 

 composed plant residues but not in the soil 

 itself. 



