250 NATURE OF ANTIBIOTIC ACTION 



early lag phase and the logarithmic phase of multiplication, penicillin 

 has a strong inhibitory effect, completely stopping oxygen uptake, even 

 in small concentrations. It was concluded that penicillin exerts a bac- 

 tericidal effect on Staphylococcus before actual division occurs, or after 

 one division during the logarithmic phase. It appears to interfere with 

 some metabolic function of the early stages of bacterial development. 



Bonet-Maury and Perault (73), using the differential photometer, 

 suggested that penicillin stops proliferation of S. aureus almost imme- 

 diately and lysis follows. A second proliferation occurs regularly, fol- 

 lowed by a second partial lysis and then a second post-lytic growth. 

 Gardner (312) reported that high penicillin concentrations (50 to lOO 

 O.U./ml.) slowly kill bacterial spores. B. anthracls spores were more 

 susceptible than those of B. subtilisy although neither were completely 

 eliminated by penicillin. 



The relation between antibiotics and bacteriophage has attracted con- 

 siderable attention. Gratia (353) observed a definite relation between 

 the action of lysozyme and the liberation of bacteriophage. The action 

 of antibiotic agents, however, is usually quite different from that of bac- 

 teriophage (352, 677). Filtrates of cultures of homologous bacteria are 

 able to inactivate the anti-coli phage j at 27° C, the inactivation is pro- 

 portional to the phage and filtrate concentration j at 0° C, to the square 

 root of the latter (231). Based upon the formation of iso-antagonistic 

 substances, a method has been suggested (132) for the differentiation 

 of bacteria belonging to the typhoid group. 



EFFECT OF ANTIBIOTIC SUBSTANCES UPON THE 

 MORPHOLOGY OF MICROORGANISMS 



Emmerich and Saida (238) were the first to report that anthrax bac- 

 teria undergo morphological changes as a result of the action of pyocya- 

 nase. Since that early work, the effect of bacterial filtrates upon cell 

 multiplication and cell growth has been made the subject of many in- 

 vestigations. It was reported (381), for example, that no complete ces- 

 sation of the fission process of bacteria results from the action of the 

 substance, but that growth itself is checked, the action being nonspecific 

 as far as bacterial species are concerned. The conclusion was reached that 



