R. D. HOTCHKISS 



rials for synthesis of protoplasmic constituents in growth. We have 

 some evidence that it is with one of these energy-utilizing functions 

 that gramicidin interferes. 



The useful form of energy derived from such processes very 

 commonly appears to be the phosphate ester. An organic substance 

 phosphorylated at the proper place is thereby activated for oxidation 

 or other conversion in much the same way that a wooden match tipped 

 with a phosphorus composition is prepared for a function in which a 

 plain wooden splinter would be inert. Since bacteria, when growing, 

 are performing a great many complicated chemical reactions, it is very 

 important that we are sometimes able to study the first beginnings of 

 synthesis in the phosphorylations and accumulation of intermediates 

 that accompany respiration in washed, nonproliferating bacterial sus- 

 pensions. In such preparations of staphylococci, normal oxidation 

 of substrates results under certain conditions in the accumulation 

 inside the cells of: (a) phosphate, at the expense of external inorganic 

 phosphate; and (b) an unidentified phosphorylated carbohydrate ester. 

 In the absence of nutrients, these events appear to represent the most 

 that can be accomplished toward growth. But both of these events are 

 virtually abolished by gramicidin in the same small concentrations 

 that suffice to prevent bacterial growth in a more satisfactory environ- 

 ment. In short, gramicidin does not prevent staphylococci from con- 

 suming substrate, but appears to prevent them from deriving benefit 

 from the act. It is tempting to conclude that this effect accounts for 

 the growth-inhibitory properties of gramicidin. There is some evi- 

 dence in favor of this. The prevention by gramicidin of inorganic 

 phosphate uptake, at least, is remarkably clear-cut and requires but 

 small amounts of the agent. Under various conditions with different 

 susceptible and resistant strains, different species, in altered environ- 

 ments, and with and without gramicidin antagonists, this effect parallels 

 the ability to prevent growth. 



As yet, it is not possible to suggest which specific enzyme is 

 being inhibited in this effect of gramicidin, although it appears quite 

 likely that the phenomena observed can result from the blocking of a 

 single enzyme. Naturally, therefore, it is not possible to judge whether 

 gramicidin inhibits because it resembles the natural substrate, but it 

 appears improbable that a polypeptide-like substrate would be in- 

 volved in these reactions. So we may tentatively look upon the action 



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