EFFECT ON PHYSIOLOGY OF THE BACTERIAL CELL 215 



swelling and bursting of the elongated cells. It was recognized that 

 these changes were due to a failure of fission. Cell growth not accom- 

 panied by cell division underwent autolysis, Br. abortus and Br. meli- 

 tensis, which were not inhibited by penicillin even at i : i,000 dilution, 

 gave no enlargement of the cells but showed vacuolation even in lower 

 dilutions. CI. "xelchiiy which was inhibited by i : 6o,000 penicillin, 

 showed filament formation in a dilution of i : 1,500,000. The phenom- 

 ena of swelling and lysis were said ( 833 ) to be associated with the active 

 growth of the bacterial cell. Suspensions of fully grown bacterial cells 

 showed neither of these effects when added to concentrations of peni- 

 cillin many times higher. It was suggested that penicillin either has 

 some action on the cellular wall of S. aureus or that it interferes with 

 the assimilation of one or more growth factors necessary for the fission 

 of the growing cell. 



A growth-depressing substance, which altered the type of growth of 

 both fungi and bacteria, was also isolated (144) from yeast. Fungi 

 treated with this substance produced thick gnarled mycelia and formed 

 no conidia or pigment. Increasing the concentrations of the depressing 

 agent changed the nature of the colony of E. colt from smooth to rough 

 and finally to grainy j this was associated with an increase in the length 

 of the cell and the formation of filaments. When the cultures thus modi- 

 fied were placed in media free of the agent, normal, highly motile cells 

 were again produced. 



The mechanism of disintegration of the hyphae of a plant pathogenic 

 fungus Rhvzoctoma by an antagonistic fungus Trichoderma as well as 

 by the antibiotic product of the latter has been described by Weindling 

 (962). The hyphae are usually killed in less than 10 hours, as shown by 

 loss of the homogeneous appearance of the protoplasm and of the 

 vacuolate structure of the hyphae, which either become empty or as if 

 filled with granular material. 



ANTIBIOTIC SUBSTANCES AND THE PHYSIOLOGY 

 OF THE BACTERIAL CELL 



Half a century ago Smith (838) emphasized that bacteria growing 

 in mixed cultures undergo temporary and even permanent physiologi- 



