248 



NATURE OF ANTIBIOTIC ACTION 



Figure 26. Spirocheticidal action of various amounts of penicillin in vitro. 

 Inoculum, 4x10* organisms per milliliter. From Eagle and Musselman 

 (225). 



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. coli 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- 



