CHAPTER XII 



THE ROLE OF BACTERIA IN THE CULTIVATION 

 OF INTESTINAL PROTOZOA 



By 

 Herbert Ratcliffe 



School of Medicine, University of Pennsylvania 



To date no intestinal protozoon from mammals has been grown 

 in culture except in the presence of bacteria. It has been known for 

 some time that many species of intestinal protozoa ingest bac- 

 teria in the intestine of the host and in cultures, but, until re- 

 cently, nothing was known as to the importance of bacteria in 

 cultures of protozoa or the relative suitability of various types of 

 intestinal bacteria as food for intestinal protozoa. It was ob- 

 viously impossible to determine the importance of bacteria in 

 cultures or the relative value of different species without first 

 separating the protozoa from the bacteria. 



Attempts have been made to free protozoa of bacteria but, 

 with the exception of TritricJiouwnas fccalis Cleveland, all attempts 

 have failed. It seems probable, with the technique employed by 

 Cleveland (1928), that other species will also be separated from 

 bacteria, and similar studies made on other organisms. Dr. Cleve- 

 land's methods are quoted. 



*'It is obvious that, in order to free trichomonads of bacteria, it 

 is necessary, first of all, to develop a culture medium which is 

 at least as well-suited to the growth of the trichomonads as to 

 the growth of the bacteria. Most media in which trichomonads 

 have been cultivated are much better suited to the growth of the 

 bacteria. Consequently, an efifort was made to develop a medium 

 (or to find a condition) as well-suited to the growth of the 

 trichomonads as the bacteria. Many experiments were carried 

 out which, owing to the fact that they were negative, that is, 

 did not yield the desired result, will not be mentioned. Various 

 chemicals were used with the hope that some of them would 



112 



