BACTERIOSTATIC AND BACTERICIDAL AGENTS 211 



Quinones have a high bactericidaJ power (145, 147, 615, 948), due 

 not to their chemical interaction with the cell proteins but to their re- 

 activity with the simpler cell constituents such as some of the amino 

 acids (146, 148). Only a slight difference was found in the apparent 

 activity of quinones toward yeasts, bacteria, proteins, peptones, pep- 

 tides, and certain amino acids. Alcohol increases the germicidal power 

 of the quinones. Actinomycin 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 biological nature of this antibiotic agent and of quinones. 

 On the other hand, many of the antibiotic substances produced by fungi 

 are typical quinones and act as such. 



By varying the concentrations of disinfectants, the types of curves of 

 destruction of bacterial cells were found (694) to range from linear to 

 an abrupt drop to zero at critical concentrations. This is brought out in a 

 study of the spirocheticidal action of penicillin (Figure 25). 



In general, chemical disinfectants act upon bacteria in four different 

 ways: (a) some affect the lag phase of the growth period, (b) some in- 

 fluence the mechanism of cell division, (c) some influence the metabolic 

 processes, and (d) some affect the death rate of the microbes. Similar, if 

 not greater, variations are found in the nature of the action of antibiotic 

 substances of microbial origin upon the bacterial cell. 



Gramicidin inhibited dehydrogenase activity, since the antagonized 

 bacteria rapidly lost their capacity to reduce methylene blue in the pres- 

 ence of glucose. E. colt suspension treated with actinomycin lost its 

 capacity to reduce methylene blue before the cells were completely 

 killed. The oxidation of succinic acid by tissue preparations, which re- 

 quire the cooperation of succinic dehydrogenase and a cytochrome sys- 

 tem, was strongly inhibited by pyocyanin. This inhibition exhibited cer- 

 tain interesting peculiarities : in low concentrations, pyocyanin strongly 

 inhibited the activity of the complete succinic cytochrome system but 

 had no effect on the oxidation of succinic acid through methylene 

 blue J in the presence of KCN, pyocyanin acted as an autoxidizable hy- 

 drogen acceptor similar to methylene bluej glutaminic acid did not af- 

 fect the inhibitory action of pyocyanin. This inhibitory action was found 

 to be due not to the formation of oxalacetic acid but to a direct effect on 



