MECHANISM OF ANTIBIOTIC ACTION 225 



The agent interferes with various enzymatic systems, such as the respira- 

 tory mechanism of the bacterial cell, especially the hydrogenase sys- 

 tem (449) and the phosphate uptake by the bacteria accompanying 

 glucose oxidation, as in the action of gramicidin. Penicillin, for ex- 

 ample, inhibits the production of coagulase by staphylococci in vitro 

 (590). 



The antibiotic substance may inhibit directly cellular oxidations, particu- 

 larly those involving nitrogenous compounds, an action similar to 

 that of propamidine (521). 



The antibiotic substance acts as an enzyme system and produces, in the 

 medium, oxidation products, such as peroxides, injurious to the bac- 

 terial cell. The glucose oxidase produced by P. notatum catalyzes 

 the following reaction : 



Glucose + HoO + Oo -> Gluconic acid + HoOo. 



The antibiotic substance favors certain lytic mechanisms in the cell, 

 whereby the latter is destroyed; this mechanism may be either sec- 

 ondary or primary in nature. 



The antibiotic substance affects the surface tension of the bacteria, acting 

 as a detergent; tyrocidine lowers the surface tension of the bacterial 

 cell, thereby causing its death, possibly by forming a stable complex 

 with it (200). 



The antibiotic substance may interfere with the sulfhydryl group which is 

 essential for cell multiplication. This was shown by Fildes (254) to 

 hold true for mercurials and other chemical antiseptics as well as for 

 true antibiotics such as clavacin and penicillic acid (325 ). 



The interaction of sulfhydryl-containing compounds with antibiotics 

 depends on the nature and concentration of the latter. It has been sug- 

 gested (118) that the activity and specificity of an antibiotic are func- 

 tions of several factors, such as its diflusibility into the microbial cell, its 

 adsorption by various enzyme systems, its reaction with sulfhydryl 

 groups of the enzymes or with other sulfhydryl-containing substances 

 adsorbed by the enzyme. Gliotoxin and the active principles of Allium 

 sativum and Arctium minus showed little specificity in reactivity toward 

 the thiols, whereas penicillin, streptornycin, and the Asarum canadense 

 antibiotic reacted more readily with those sulfhydryl compounds which 

 contained basic amino groups in the vicinity of the — SH. Pyocyanin 

 had intermediate properties (115b). 



