CHAPTER XII 



CLASSIFICATION, MORPHOLOGY, AND BIOLOGICAL 

 ACTIVITIES OF THE ACTINOMYCETES 



Henrici stated that "no group of microorganisms presents so much 

 difficulty in classification as that now generally designated Actino- 

 mycetes." The difficulty which Henrici found, in 1930, has now, in 

 1945, partly because of his own writ- 

 ings, resolved itself into a more logical 

 and orderly system. Of necessity, clas- 

 sification of any group of plants or 

 animals precedes intimate knowledge 

 of these forms. This preliminary clas- 

 sification stimulates research on the 

 organisms classified. Later, when this 

 knowledge has been obtained and has 

 been disseminated, reclassification is 

 necessary. In the interim and until 

 the newer classifications are accepted, 

 there is difficulty and confusion. 



Classification. The actinomycetes 

 contain organisms that are definitely 

 mold-like and bacteria-like. The most 

 mold-like actinomycetes resemble the 

 Fungi Imperfecti more closely than 

 they do the bacteria-like actinomy- 

 cetes, and the most bacteria-like 



actinomycetes are closer to the tubercle and diphtheria bacilli than 

 they are to the mold-like actinomycetes. 



Many of the actinomycetes possess a well-developed mycelium 

 and reproduce by conidia, usually in chains. Occasionally some of 

 the mycelium may segment into arthrospores. Most of the mycol- 

 ogists studying these organisms ignored the bacteria-like actinomy- 

 cetes and have classified the whole group as Fungi Imperfecti, or 

 have given them a rank as a separate class between the Fungi Im- 

 perfecti and the Schizomycetes. Thus Vuillemin, in his classification 

 of the Fungi Imperfecti, first included the actinomycetes as a sepa- 



349 



Fig. 127. Conidia and conidio- 

 phores of Streptomyces coeli- 

 color. Drawn from slide cul- 

 ture. Note that both dextrorse 

 and sinistrorse spirals are found 

 in the same preparation. 



