NOMIlNCLATrUI': AM) ( IIINI'.H AL SVSTIIMS OF Cl.ASSIFKWTION 



69 



'ri\i> strains of Nocardia studied were scp- 

 rated, on the basis of th(> cultuiai data pre- 

 sented, into "tnie" Xocdnhd and "strepto- 

 myees-like" Xocardia. Tlu^ foiiuer liave l)ocn 

 fiirtlier tentatively diviiled into the follow- 

 ing groups: (a) X. astcroidcs group (all strains 

 of N. astcroidcs plus N. blackweltii, N. cunic- 

 uli, X. caprac, N'. sijlvodorifcra, N. pohj- 

 chromogcncs, X. minima, and iV. paraffinac); 

 (b) .V. corallina {X . globcnda, X. crijthrop- 

 olis, and X. convohita); and (c) .V. opaca 

 group (.V. opaca and .V. rubra) (Table 12). 



\'arioiis other criteria ha\'e been suggested 

 as aids in the classification of the actino- 

 mycetes, notal)ly members of the genus 

 Strcptomyccs. It is sufficient to mention 

 phage susceptibility (Stocker) and forma- 

 tion of antibiotics (Kurosawa, Kuroya, ct al., 

 1950). According to Krassiluikov (1957), 

 antibiotics may be considered as necessary 

 in the struggle for life between rival organ- 

 isms. They manifest their activity toward 

 competing organisms only, but never against 

 cultures of the same species. He believed that 

 strains of one species produce antibiotics 

 inhibiting the growth of all the strains of 

 rival species. This antagonism may be uni- 

 lateral or bilaterial. He suggested that the 

 specificity of antibiotics produced by various 

 species be used in taxonomy for the differ- 

 entiation of these species. He reported suc- 

 cess in demonstrating, by means of cross 



antagonism exp(>riments, the heterogeneity 

 of many species which heretofore were con- 

 sidered as homogeneous. 



Wak.sman and Lechevalier found that, on 

 the basis of sensitivity to isoniazide, the 

 phylogenic j)()sition of the various Actino- 

 mycetales was indicated as follows: The 

 pathogenic forms of the genus Mycobac- 

 terium are susceptible to less than 1 mg of 

 isoniazide per milliliter, the avian form l)eing 

 least susceptible; the saprophytic forms were 

 less susceptible, some being resistant to 100 

 and even 1000 mg per milliliter, most of them 

 being susceptible to less than 5 and 10 mg 

 per milliliter. The micromonosporas were 

 more resistant to isoniazid than the myco- 

 bacteria (10 to 1000 mg per milliliter). The 

 nocardias were also moderately more resist- 

 ant, most of them re(iuiring 80 to 300 mg of 

 isoniazide per milliliter for growth inhil)i- 

 tion; some were more susceptible (10 mg per 

 milliliter), and others were resistant (more 

 than 1000 mg per milliliter). The strepto- 

 mycetes were most resistant, requiring as a 

 rule more than 1000 mg of isoniazide per 

 milliliter for inhibition. The various genera 

 of the Actinomycetales could thus be listed 

 in the following order of increasing resistance 

 to isoniazide: pathogenic mycobacteria — ^ 

 saprophytic mycobacteria — > Micromono- 

 spora -^ Nocardia —* Strcptoinyces. 



Among the new approaches to the tax- 



Table 13 

 Classification of the actinoinyccles based on cell wall composition (Commins and Harri.s) 



* Position rather doubtful. 



+ In Micromonospora uL-diaminopiinclic acid is present in addition. 



