350 ACTINOMYCETES 



rate order under the name Microsiphonales, but later gave them the 

 rank of a family (Nocardiaceae) in his order of Arthrosporales, giv- 

 ing more weight to the fragmentation of the mycelium as a character 

 of taxonomic importance. Drechsler ^ could see no resemblance to 

 bacteria and would include them without qualification as a group of 

 the Fungi Imperfecta Lieske ^"^ prefers to consider them an inde- 

 pendent group of fungi, between the molds and the bacteria, but 



showing a more intimate relationship with 



tjPf- V^ I the bacteria than with the higher fungi. 



j N ^,__'N 5^ Waksman -^ believes that "they should be 



^__V ^ » »^^ ^ looked upon as a group of fungi, to be clas- 



<'^-s\^'^/V^c^r\\ sified separately from other groups till their 



.N \ ''V^ ^>.S_Ns^ exact systematic position has been definitely 



\^^ '^^■^.'^ established." 



^■*r ^^ > "n'^^^ Many of the actinomycetes, however, al- 



"v'^ X"^^ though they for a time have a definite branch- 



FiG. 128. Smear prepara- ^^g mycelium, ^ very soon fragment com- 



tion from a culture of pletely into bacillary or coccoid arthrospores 



Actinomyces bovis, show- and these Continue to divide by transverse 



ing bacterial forms re- figgion. At this stage they resemble ordinary 



suiting from fragmenta- bacteria very closely. The degree to which 



tion of myselium. When ,, • ^ , ,. . .,t , i 



rapidly subcultured the this fragmentation occurs varies with the 



growth becomes purely species or with different cultures of the same 

 bacteria-like, no myce- organisms, but is most frequently encoun- 

 lium developing. Note tered in the pathogenic species. In such 

 the resemblance to diph- ^^^^^^ ^j^^ development of aerial mycelium 

 theroid bacteria. ,. , , i ^ i i i • 



may be very snght or completely lacking. 



On the other hand, when rapidly subcultivated, such forms may fail 

 to develop any mycelium or the mycelium may be so fragile that it 

 dissociates when mounted for examination, the growth appearing 

 precisely like a somewhat pleomorphic bacterium, such as the diph- 

 theroid organism. This observation led early to the view that the 

 actinomycetes are but higher forms of bacteria. That they are 

 closely related to the bacteria is also indicated by the occurrence of 

 acidfast species of actinomycetes which bear a close resemblance to 

 the tubercle bacilli, not only in morphology, but also in cultural char- 

 acters, pathogenicity, and immunity reactions. This relationship is 

 so clearly established that there can remain no doubt that some of 

 the actinomycetes, at least, are phylogenetically very close to the 

 Mycobacteria. Puntoni -" has recently called attention to the bio- 

 chemical, morphological, and immunological similarities between the 

 anaerobic Actinomyces bovis and Lactobacillus bifidm. 



