DIFFERENTIATION OF BACTERIA 219 



blood serum were found to inhibit the action of gramicidin. Because of 

 this, cephalin is capable of reviving bacterial cells killed with grami- 

 cidin. This phenomenon is similar to the inhibition by phospholipins of 

 the action of synthetic detergents upon bacterial metabolism (35). 

 Mucin inhibits the action of tyrothricin, especially on meningococci and 

 pneumococci (182). 



Tannic acid is able to neutralize the antibiotic action of actinomycin. 

 Humus compounds of the soil have a similar capacity. This effect was 

 believed to be responsible for rendering harmless, to living plant and 

 animal forms, the actinomycin produced in the soil (947). Ascorbic acid 

 also has an effect in reducing the activity of this substance. Jungeblut 

 (466) demonstrated that vitamin C, interacting with atmospheric oxy- 

 gen, leads to the production of destructive peroxides in a medium. Since 

 vitamin C is a strong reducing agent and actinomycin is a reversible 

 oxidation-reduction system, it is conceivable that actinomycin may be 

 reduced through the action of the vitamin. Such an effect should be 

 greatly increased under anaerobic conditions, where no reoxidation due 

 to atmospheric oxygen could occur. Twenty-five to 50 times as great a 

 neutralizing effect of ascorbic acid upon actinomycin was obtained un- 

 der anaerobic conditions with CI. butyricum as a test organism as under 

 aerobic conditions with B. niycoides. Reduced actinomycin was inactive. 

 It was concluded, therefore, that the neutralizing action of ascorbic 

 acid upon actinomycin was due merely to its reducing properties. As far 

 as the common growth factors are concerned, the action of actinomycin, 

 like that of penicillin, differs from the mechanism proposed by Woods 

 (1003) and others for sulfanilamide inhibition. 



DIFFERENTIATION OF BACTERIA BY MEANS 

 OF ANTIBIOTIC SUBSTANCES 



Because of their selective action upon different bacteria, antibiotic 

 substances can be utilized for separating bacteria from one another. 

 Fleming (269) utilized penicillin to isolate Pfeiffer's bacillus and the 

 pertussis organism of various cocci, diphtheria, and neisseria organisms j 

 the substance was found to behave as the mirror image of tellurite in 

 inhibiting specific bacteria. Penicillin was also utilized for the separation 



