246 NATURE OF ANTIBIOTIC ACTION 



The bactericidal action of antibiotic agents, as influenced by their 

 concentration, can be illustrated by the action of pyocyanase (Table 

 40). In a study of the bactericidal action of actinomycin (975) it was 

 found that the addition of 0.5 mg. of actinomycin to a 10 ml. sus- 

 pension of E. coli reduced the number of viable cells from 6,400,000 

 to 493,000, the methylene blue reduction test remaining positive j 

 I mg. actinomycin reduced the number of cells to 4,800, the reduction 

 test becoming negative j 2 mg. of the agent brought about complete de- 



TABLE 40. BACTERICIDAL ACTION OF PYOCYANASE UPON THREE BACTERIA 



From Emmerich, Low, and Korschun (237). 



struction of all the cells. The bactericidal action of actinomycin seems 

 to be a result of a chemical interaction similar to that of other anti- 

 septics. On adding o.i mg. actinomycin to a suspension of E. coli cells 

 in a 10 ml. buffer solution, the value of the constant K was found to 

 vary from 0.021 to 0.026 for different periods of incubation. Figure 25 

 illustrates graphically the effect of different concentrations of actino- 

 mycin on the death rate of E. coli in buffer solution. 



Quinones have a high bactericidal power (153, 977), due not to 

 their chemical interaction with the cell proteins but to their reactivity 

 with the simpler cell constituents such as some of the amino acids. Only 

 a slight difference was found in the apparent activity of quinones 

 toward yeasts, bacteria, proteins, peptones, peptides, and certain amino 

 acids. Alcohol increases the germicidal power of the quinones. Acti- 

 nomycin contains a quinone group ; however, it acts differently toward 

 gram-positive and gram-negative bacteria j alcohol has no effect upon 

 its action, thus pointing to marked differences in chemical and biologi- 



