102 



THE ACTINOMYCETES, Vol. I 



HOURS OF INCUBATION 



Figure 49. Mutagenic and lethal effects of 

 ultraviolet radiation (Reproduced from: New- 

 combe, H. B. Mutation. Brookhaven Symp. in 

 Biol. No. 8, 1956, p. 90). 



nature have been reported. It is sufficient 

 to mention the work of Novak and Henrici 

 on the appearance of a yellow staphylococcus 

 in a Berkefeld filtrate of a broth culture of a 

 saprophytic actinomycete. The staphylococ- 

 cus was found to change first into rods, then 

 into long branched filaments which could 

 not be distinguished from true actinomycete 

 hyphae. The coccus also dissociated first into 

 S- and R-forms, then into filterable G-forms. 

 Krassilnikov described a micrococcus as 

 merely a stage in the normal development of 

 the nocardias, rather than as an abnormal 

 mutant (see also Levy, Karwacki, Koelz). 



In general, two opposing concepts served 

 as the basis for explaining the variations 

 among the actinomycetes. On the one hand, 

 there is the two-phase life cycle concept of 

 species, described previously. On the other, 

 there is the earlier and generally accepted 



complex of the asexual character of the acti- 

 nomycetes (Jones). 



The two-phase life cycle concept of species 

 of Streptomyces assumes a haploid substrate 

 mycelium and a diploid aerial growth. Ac- 

 cording to Badian (1936), chromatin mate- 

 rial is distributed through the hyphae in the 

 form of chromosome-like bodies; these unite 

 just before spore formation takes place, so 

 that each spore has a bivalent chromosome. 

 On germination of the spores, the bivalent 

 chromosome undergoes two divisions. One 

 of these is a reduction division; the one to 

 three germ tubes each recei\^e one of the 

 four chromosomes; the remaining chromo- 

 somes gradually disintegrate. 



Klieneberger-Nobel accepted this concept, 

 designating the fused cell of the primary 

 (substrate, haploid) mycelium as an "initial 

 cell" which produces the aerial or secondary 

 mycelium. Morris also accepted this concept 

 for A . bovis and recognized two fusions in its 

 life cycle. According to Webb et al., the 

 nuclear process during fragmentation in N. 

 corallina "appears to give rise to binucleated 

 bacillary cells. Coccoidal cells, however, are 

 observed to be uninucleate." The cytological 

 results of Badian were believed by Stanier 

 to provide a possible basis for explaining 

 spore variations. This process of spore forma- 

 tion w^as thought to be responsible for the 

 great variability of actinomycetes. 



Krassilnikov and Tausson suggested other 

 mechanisms of variation operative through 

 a nonconidial phase of growth. According to 

 Schaede and \on Plotho, the bodies w^hich 

 Badian took for chromosomes are actually 

 condensed cytoplasm. The long-accepted 

 view is that the streptomyces is an asexual 

 organism in which the individual is differ- 

 entiated into a substrate mycelium and an 

 aerial myc^elium reproductive l)y means of 

 spores; the latter may arise directly as a 

 branch from any vegetative hypha at any 

 point. This concept has recently been modi- 



