LVl'K" .M1:C1IAN1S.M8 



171 



1. Tlu' j^rowtli phase, cliaracterizi'd hy for- 

 mation of inyccliuin, ri'ductioii of soluhlo 

 imlricnts in the nii'dinni, production and 

 utilization of lactic acid, a lii^h oxyj^cn de- 

 mand, and little production of streptomycin. 



2. Till' aulolytic phase, chai-acterized hy a 

 marked decrease in \\eiij;ht of mycelium, an 

 increase in inorganic phosphorus and soluble 

 nitrogen in the medium, a droi) in oxygen 

 demand to zero, and production of large 

 quantities of streptomycin. 



Increases in carbohydrate or jjhosphate 

 content of the medium have but little effect 

 on the general changes, although they may 

 lengthen the growth phase. \'arious strains 

 show no significant differences in the meta- 

 bohc changes, although they may show 

 marked differences in streptomycin produc- 

 tion. 



8chatz and Waksman (1945), studying the 

 production of streptomycin by different 

 strains of S. griscus, observed that colonies 

 devoid of aerial mycelium formed no strepto- 

 mycin (Dulaney found exceptions). Such 

 colonies gave rise to cultures that underwent 

 much more rapid lysis than the normal cul- 

 tures with aerial mycelium. In the practical 

 production of streptomycin, it is generally 

 ob.served that, under submerged conditions 

 of growth, maximum formation or accumula- 

 tion of the antibiotic corresponds to the be- 

 ginning of lysis; advanced lysis usually re- 

 sults in a rapid destruction or inactivation of 

 the streptomycin already produced. 



In further studies, it was found that S. 

 griscH.s may give rise to two types of inac- 

 tive strains. One of these is free from aerial 

 mycelium. In culture, especially in a sub- 

 merged condition, it undergoes rapid lysis. 

 It gives rise to an acid reaction in the me- 

 dium and yields a viscous broth. This strain 

 is sensitive to the antibiotic action of strep- 

 tomycin and is comparable in that respect 

 to other inactive actinomycetes, whereas the 

 streptcjmycan-producing strains are highh' 



resistant to the action of this antibiotic. 

 This \ariant is similar to th(! active culture 

 in such cultin-al cliaracleristics as lack of 

 dark pigmentation on organic media, proteo- 

 lytics action, and hemolytic capacity. By 

 pioper culture and selection, this asporogen- 

 ous strain can be made to revert to the 

 sporulating strain, which will have the ca- 

 j)acity of producing streptomycin. Some as- 

 porogenous strains are definite mutants, ac- 

 cording to Appleby. 



According to Lvnnb, *S'. griscu.s undergoes 

 lysis more rapidly under submerged condi- 

 tions of growth than under stationary condi- 

 ti(jns. The culture tends to become viscous as 

 a result of formation of the lysed material. 

 *S'. fradiac, the culture that produces neomy- 

 cin, behaves in the same way. Lumb also 

 observed that the accumulation of the anti- 

 biotics corresponds to the beginning of lysis. 



Various attempts have been made to cor- 

 relate the phenomena of autolysis among the 

 actinomycetes and their bacteriolytic action 

 upon gram-positive bacteria. Although both 

 seem to involve the hydrolysis of proteins, 

 bacteriolj'sis involves lower proteolytic ac- 

 tivit.y, is active at a different pH le\'el, and 

 proceeds further than autol3^sis. 



Gorjunova considered the process of lysis 

 among actinomycetes as enzymatic in na- 

 ture, since it is accompanied by the break- 

 down of proteins. According to her, the lytic 

 agents consist of two components that can 

 be separated by dialysis. Neither of these is 

 active by itself, but when the two are mixed, 

 they bring about the Ij^sis of the cultures. 



Bacteriolysis 



The first observations on the lytic effect 

 of actinomycetes upon other organisms were 

 made by Ciasperini in 1890. He reported that 

 actinomycetes are able to grow on the surface 

 of cultures of bacteria and fimgi, living as a 

 sort of parasite upon these organisms, and 

 are capal)le of digesting them. 



