102 BACTERIA AS ANTAGONISTS 



another race and caused an agglutination of the latter in fluid media. 

 The weakest antagonists were said (387) to belong to the paracolon 

 group, the strains of medium activity to the colon group, and the 

 strongest antagonists to the colon-immobilis type. Whenever the feces 

 were found to contain large numbers of E. colt, no typhoid organisms 

 were present. The resistance of certain persons to intestinal diseases 

 was, therefore, ascribed to the high antagonistic colon index. By utiliz- 

 ing the principle of antagonism of some strains of E. coli against others, 

 two types of E. coli resistant to the antagonistic substance were isolated 

 ( 176) : one produced giant colonies, the other small punctiform, trans- 

 lucent colonies. 



More recently it was established (357a) that various strains of E. coli 

 produce a complex mixture of antibiotics, designated as colicines, which 

 are mostly bacteriostatic against certain other strains of this organism 

 as well as against other pathogenic enterobacteria. On the basis of their 

 selective action, concentration, diffusibility, thermostability, and sensi- 

 tivity to antagonistic organisms, eight groups of substances were listed. 

 They represent polypeptides readily destroyed by trypsin. 



E. coli exerts an antagonistic action also upon S. schottmulleriy C. 

 di'phtheriae, staphylococci, M. tuberculosis, B. anthracis, various spore- 

 forming soil bacteria, and putrefactive water bacteria. The action 

 against anthrax was said to be only temporary (344). It was also sug- 

 gested (457) that only living cultures of E. coli are active. The simul- 

 taneous inoculation of S. aureus and E. coli was found (769) to be in- 

 jurious to the first and not to the second organism j this effect was in- 

 creased by an increase in the number of E. coli cells in the inoculum. 

 Gundel and Himstedt (368) have shown that E. coli, but not ^. aerog- 

 enes, is antagonistic to S. aureus and S. albus. 



The term autophage has been used (342) to designate the process of 

 clearing a water emulsion of dead cells by a culture of an antagonist 

 such as E. coli. This clearing effect was said to be due to the fact that the 

 dead cells are used as nutrients by the living organism. The mechanism 

 of the action was variously explained by a change in the />H value of 

 the medium or in the oxidation-reduction potential or by a direct enzy- 

 matic effect. In some cases thermolabile, filterable substances were dem- 



