224 



THE ACTIXOiMYCETES, Vol. I 



sirable property for species differentiation 

 (Table 59). Umezawa, Oki and Hata, 

 Kuroya, and others also accepted this con- 

 cept for classifying actinomycetes. 



Teillon (1952), who made a detailed study 

 of the cross-resistance of actinomycetes pro- 

 ducing antibiotics, found various important 

 exceptions to the principle expostulated by 

 Kuroya and Krassilnikov (Table 59) . On the 

 basis of these results, he expressed doubt 

 concerning the validity of the claim of the 

 Japanese investigators that "the cross-inhibi- 

 tion test is a useful and easy method of dif- 

 ferentiation." The method of cross-inhibi- 

 tion did not appear to Teillon as sufficiently 

 reliable for differentiating streptomyces cul- 

 tures and their antibiotics. The organisms 

 were shown to form a variety of metabolic 

 products that could readil}^ mask the results. 

 Further, some organisms produced certain 

 other antibiotics that, although in them- 

 selves possibl}'- not quantitatively significant. 



modified the effects of the major antibiotics 

 produced by the organisms. Some strains 

 related to *S'. griseus were able, for example, 

 to produce streptothricin as well as strepto- 

 mycin. Phenomena of autoinhibition are also 

 not uncommon among actinomycetes, such 

 as S. aureofaciens and S. fradiae. 



Finally, the quantitative variations in the 

 production of antibiotics do not permit the 

 laying down of hard and fast rules concern- 

 ing the possible effect of cross-inhibition un- 

 der natural conditions. This is brought out in 

 Table 61 on the auto- and cross-inhibition 

 of various neomycin-producing and other 

 strains of S. fradiae. It is possible to observe 

 occasionally certain self-inhibition of growth 

 by various actinomycetes, especially by pig- 

 ment-forming types. This has been ascribed 

 by Krassilnikov et al. (1958) to special sub- 

 stances of an enzymatic nature designated 

 as "necrohormones." 



