THERMOPHILIC ACTINOMYCETES 



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mycetes. The spores of these organisms were 

 found to lose their vitality rapidly, especially 

 on agar media, bu1 they survived on hay 

 particles. One culture was designated as A. 

 thermophilus Berestnew; it grew besl a1 

 40-50°C, more slowly at 30°C, and not at 

 all at 25°C and at 60°C. The manner of 

 spore formation of this organism suggested 

 its resemblance to Micromonospora. Miehe 

 also reported, however, that he saw thermo- 

 philic actinomycetes which formed spores 

 according to the manner described by Gil- 

 bert. This suggests the probability that he 

 had representatives of the two different 

 groups. Schutze (1908) found, in decompos- 

 ing clover hay, representatives of these two 

 thermophilic actinomycetes, one of which 

 appeared to belong to the Streptomyces 

 group and the other to the Micromonospora. 



Several methods for isolation and cultiva- 

 tion of thermophilic actinomycetes have 

 been described by Henssen (1957). Uridil 

 and Tetrault (1959) suggested the incorpora- 

 tion of colloidal silica in a highly proteinace- 

 OUS medium for the growth of these organ- 

 isms. 



The various thermophilic forms have often 

 been classified under the common name of 

 "Actinomyces thermophilus." Waksman et ol. 

 (1939) demonstrated, by direct microscopic 

 studies, that these organisms are very abun- 

 dant in high temperature composts of stable 

 manures and plant residues. Six distinct 

 types or species were recognized, belonging 

 to two genera, one now known as Strepto- 

 myces and the other as Micromonospora. 

 Two of the first group (S. thermophilus and 

 S. thermofuscus) and three of the second 

 (.1/. vulgaris, M. chalcea, and M. fused) were 

 isolated and cultivated. Henssen ( 1957) con- 

 firmed these observations and created sev- 

 eral new genera and species, to include these 

 and other forms (Fig. 59). 



Kosmatchev (1959) emphasized the need 

 for separating the thermophilic from the 

 mesophilic actinomycetes. since the former 

 grow at oo°C and the latter cannot be 



"•• «k 



Figure 58. First photograph of a Thermoactino 

 myces (Reproduced from: Tsiklinsky, P. Ann. 

 inst. Pasteur 13: 500-505, 1899). 



adapted to grow at that temperature or 

 under thermophilic conditions. The thermo- 

 philic actinomycetes form a sharply defined 

 ecological and widely distributed group of 

 microorganisms, and retain their thermo- 

 philic properties under laboratory condi- 

 tions. They were believed to comprise in- 

 dependent species. He suggested, however, 

 that no specific thermophilic genera be 

 recognized, but that they should be included 

 among the mesophilic forms. 



Henssen (1957) proposed a distinct system 

 for classifying thermophilic actinomycetes. 

 This system is used, with certain modifica- 

 tions, in this treatise. 



Classification of Thermophilic Actino- 

 mycetes 



A. Substrate mycelium unseptated. Spores pic 

 duced on aerial mycelium only. 



I. Aerial hyphae branched; they are almost 

 completely transformed into spore chains. 

 Streptomyces Waksman ami Henrici 



