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THE ACTINOMYCETES, Vol. I 



multiplication, they were dissolved by the 

 lytic substance. For instance, cells of E. coli 

 acted upon by radium emanation, which 

 stops their multiplication, became suscep- 

 tible to the lytic substance. 



Actinomycetin was shown to consist of a 

 protein-enzyme system, active particularly 

 upon gram-negative bacteria and upon cer- 

 tain living gram-positive bacteria. The pre- 

 cipitated preparation was found also to 

 possess bactericidal properties. This "bac- 

 tericidin" was believed to exist in the culture 

 filtrate as a harmless substance, which was 

 activated on precipitation. 



Further studies brought out the fact that 

 the lytic principles of actinomycetes are 

 rather complex in nature. They frequently 

 contain as many as four substances that dif- 

 fer in their action and in the organisms acted 

 upon. The lysis of living bacteria by actino- 

 mycetin preparations was considered to be a 

 result of two factors: (a) one acting upon the 

 living cell, being a bactericidal factor; and 

 (b) the other acting upon dead cells, being a 

 bacteriolytic factor. The second factor is 

 helped along by the process of autolysis. 

 Later, Welsch (1947) designated the bacteri- 

 cidal substance as ribonudeinase and the 

 lytic principle as actinozyme, which is the en- 

 zymatically active protein. This enzyme is 

 excreted by the organism in the process of 

 sporulation. The presence of carbohydrates 

 favors its production in artificial media. 



Muggleton and Webb (1952) also demon- 

 strated that the exocellular bacteriolytic 

 system of streptomyces depends upon an en- 

 zyme of the ribonuclease type; a deoxy- 

 ribonuclease was also present in the culture 

 filtrate. McCarty found that the lytic mech- 

 anisms of »S. albus are mucopolysacchar- 

 idases. 



These bacteriolytic mechanisms are widely 

 distributed among actinomycetes (Welsch, 

 1954). As many as 29 per cent of all the cul- 

 tures examined produced staphylolytic 

 mechanisms, and 48 per cent, streptolytic 



mechanisms ; the same preparation may con- 

 tain both. The antibiotic-producing organ- 

 isms form no lytic substances or only very 

 limited amounts. 



Welsch and Thuysen (1956) summarized 

 the bacteriolytic properties of S. alhus strain 

 G. Evidence was presented for the existence 

 of several specific systems: 1. A colilytic 

 agent or actinozyme, responsible for the lysis 

 of heat-killed gram-negative bacteria and in- 

 volved in the dissolution of at least some 

 heat-killed gram-positive organisms; 2. a 

 streptolytic agent, acting upon heat-killed or 

 living streptococci; 3. two pneumolytic 

 agents, one acting upon either heat-killed or 

 living pneumococci, and the other upon the 

 living only; 4. a complex staphylolytic sys- 

 tem, dissolving living staphylococci and 

 other bacteria and comprising two compo- 

 nents which, after isolation and purification, 

 were found to be specific peptidases acting in 

 synergy upon some unidentified constituent 

 of the cell wall. The enzymes of actinomy- 

 cetin which are able to dissolve living bac- 

 terial cells were considered as true antibiotics. 



The mode of action of the staphylolytic 

 systems was likened to that of lysozyme, 

 which also acts upon a constituent of the 

 cell wall of sensitive bacteria. Lysozyme pro- 

 duction by actinomycetes has been reported, 

 but differences of specificity between this en- 

 zyme and actinomycetin G were pointed out 

 previously. The unsusceptilibity of staphylo- 

 cocci to lysozyme, due to the nature of the 

 cell wall, was considered sufficient evidence 

 for discarding the idea of a lysozyme-like 

 nature of the staphylolytic agent. The nature 

 of the products liberated from cell walls by 

 the staphylolytic system definitely estab- 

 lishes that the peptidases involved are dif- 

 ferent from lysozyme, which is a pol,ysac- 

 charidase. 



As was shown also by Tai and van Hey- 

 ningen, the colilytic system is a rather spe- 

 cific enzyme, distinct from the proteases of 

 the crude actinomycetin. It possibly acts h 



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