448 Physiology 



Trypanosoma cruzi, Leishmania brasiliensis, L. donovani, and L. tropica 

 need factors in serum other than thiamine, /?-aminobenzoic acid, pyri- 

 doxine, or nicotinic acid (521). Hence, it appears that one aspect of 

 physiological specialization among the trypanosomes and their relatives 

 involves an increasing dependence upon the host for essential growth- 

 factors. 



Trichomonadida. Relatively little work has been reported on these 

 flagellates (349). Peptone solutions enriched Avith whole blood, serum, 

 and fragments of liver have supported growth of Eutrichomastix colu- 

 brorum (59), Trichomonas gallinae (T. columbae) (20), T. foetus (7, 

 163, 575), and T. vaginalis (255, 557, 558). Liver-infusion agar slants, 

 overlaid with serum-enriched Ringer's solution, also have been satisfactory 

 for T. vaginalis. The investigations of Cailleau have shown that the first 

 three species need certain growth-factors apparently not required by free- 

 living flagellates (Table 8. 3). More recently, T. vaginalis has been grown 

 in a peptone solution supplemented with acetate, maltose, about 15 

 growth-factors, and after sterilization, diluted serum and ascorbic acid 

 (536). In such a medium, two fractions of human serum — an ether-soluble 

 and an ether-insoluble aqueous fraction — are essential. Linoleic acid 

 seems to be the most active component of the ether-solvible fraction and 

 serum albumin of the ether-insoluble one. The first fraction could be 

 replaced by a mixture of linoleic and oleic acids, cholesterol, ergosterol, 

 lecithin, a-estradiol, a-tocopherol, vitamin A, and ^-carotene (537). Tri- 

 chomonas foetus has been grown in a mixture of thirteen amino acids, 

 various vitamins, and minerals (568). 



Sarcodiiia. Published reports on the Sarcodina include little more than 

 the development of suitable media for pure cultures, although detailed 

 investigations are in progress. Acanthamoeba castellanii has been grown 

 in a medium containing serum and liver fragments (44) and in a simpler 

 peptone and inorganic salt medium (45). A medium containing peptone, 

 dextrose, and inorganic salts also is satisfactory for Mayorella palestiiien- 

 sis (472, 473). Progress is also being made toward pure-culture techniques 

 for parasitic amoebae. Entamoeba invadens has been maintained bacteria- 

 free for several transfers after elimination of a single bacterial contami- 

 nant by treatment with penicillin (307). In addition, E. histolytica has 

 been grown on non-viable bacteria for more than 200 transfers (500), 

 and also in a non-particulate medium without bacteiial growth (501). 



Ciliates. Under natural conditions free-living ciliates feed mainly upon 

 ingested microorganisms. In the investigation of such natural foods, 

 strains of ciliates have been grown in cultures with other living or killed 

 microorganisms (36, 417, 418). Such "species-pure" cultures with living 

 bacteria involve complex relationships, and the ciliates tend to be 

 swamped unless the initial proportions between ciliates and bacteria are 

 satisfactory (259, 260, 261). Such relationships, particularly important 



