lIlsroiUC'Al. JiAC'KLIllUUNU 



11 



tlio size Miul color of colony aiul the color of 

 the aerial luyccliuni, under diU'ereiil condi- 

 tions of nuti'ilion, arc siilliciciil lo charac- 

 terize a specii's. |'hysiolo«i;ical proiuMi ies can 

 be used to supplement such chai'acterization. 

 Krainsky thus inliddiicrd a new approach 

 for cliaracterizin«i indi\idual species of uc- 

 tinomyeetes. Many new organisms were now 

 recognized, and th(> grc^at ahundance of many 

 species in the soil was thus estal)lished. Si- 

 nuiltaneously and indepen(l(>ntly, A\'aksman 

 and Curtis l)(\i;an their work in 1!)1."). 'i'licir 

 first paper, put)lished early in 19H), treated 

 the use of synthetic media for characterizin<>; 

 actinomycetes. l^efore compl(>ting their stud- 

 ies, h()we\-er, they became familiar with 

 Krainsk3''s work and took full ad\-antage of 

 it in describing various new species, l^nfor- 

 tunately, because of the prevailing World 

 War I, they could not obtain Krainsky's cul- 

 tures and had to depend solely on descrip- 

 tions for identification purposes. This led to 

 a degree of confusion in the identification of 

 some of the species. Incidentally, Krainsky's 

 cultures appear to have been destroyed be- 

 fore anyone else had access to them. The 

 work of Waksman and Curtis culminated in 

 a comprehensive study of the cultural prop- 

 erties of actinomycetes by Waksman in 1919. 

 Attention should also be directed, at this 

 point, to the work of Drechsler, on the mor- 

 phology of the actinomycetes. Unfortu- 

 nately, Drechsler made no attempt to isolate 

 fresh cultures from soil or other natural ma- 

 terials, but based all his studies on the cul- 

 tures submitted to him by Waksman and 

 Curtis. These were all aerial mycelium-pro- 

 ducing forms, or species now recognized as 

 members of the genus Streptomyces. 



3. Biological IWiod (1919-1940) 



During this period, not only the morpho- 

 logical and ecological propcn-ties of the ac- 

 tinomycetes were studied, but also their 

 physiological and biochemical activities. The 

 publication in 1921, of Lieske's monograph 



on the "Morphologic und i^iologie dcr Strah- 

 lenpilzc" may be considered as the begimiing 

 of this pei'iod. Some of the most outstanding 

 contributions to our knowledge of the tax- 

 onomy and classification of actinomycetes, 

 their occiiirciice in iiatui'e, and theii' antago- 

 nistic properties were recognized dui-ing this 

 period. Lieske's work, unfortunately, did not 

 exert so great an influence upon the subse- 

 (luent developments in the field as it should 

 have. This was due piimarily to the fact that 

 Lieske was not familiar with the importance 

 of synthetic media in charactei-izing actino- 

 mycetes, nor did he appreciate the fact that 

 these oi'ganisms represent munerous species 

 widely distributed in nature. This led him to 

 doubt the existence of more than a few 

 species, which thus tended to obsciu-e rather 

 than to stimulate further developments in 

 this field. 



The work of 0rskov, in 1923, on the mor- 

 phology of the actinomycetes, was highly 

 significant and stimulating, and marked a 

 turning point in the field. It pointed a way 

 toward establishing a new system of classi- 

 fication of actinomycetes, based on their 

 morphological properties. The subsequent 

 investigations of H. L. Jensen, beginning in 

 1930, on growth of actinomycetes in soil, 

 their morphological and cultural characteris- 

 tics, tended to broaden further our knowl- 

 edge of these organisms. In 1934, Duche pub- 

 lished a comprehensive monograph on the 

 actinomycetes, made up of species considered 

 to belong largely to the group Actinomyces 

 albus. This contribution did not tend to 

 elucidate the nature and activities of the 

 actinomycetes as a whole, but it emphasized 

 the marked variability of their growth on dif- 

 ferent media and the great complexity of the 

 problem invoh'ed. This work ^^•as soon fol- 

 lowed by the studies of Erikson (1935, 1940) 

 on the pathogenic actinomycetes belonging 

 to aerobic and anaei'obic groups and of Kriss 

 (1937) on the variations of actinomjcetes. 



Considei-al)le emphasis was also laid, dur- 



