Physiology 441 



Colpoda steinii (diiodenaria) (139) and Tetrahymena pyriformis (179, 

 289, 290) and probably for malarial parasites (11). The synthesis of ribo- 

 flavin by Chilomonas Paramecium (207) suggests the probable importance 

 of this vitamin in phytoflagellate metabolism. 



The pyridoxine complex. In the earlier investigations, a stimulation of 

 growth by pyridoxine was noted in several ciliates (120, 283, 317). A 

 ciliate, Colpoda steinii (545), also was the first protozoon shown to need 

 pyridoxine. Tetrahymena pyriformis has since been found to require pyri- 

 doxine, pyridoxal, or pyridoxamine, the two derivatives being 100-500 

 times as active as pyridoxine (289), a relationship similar to that pre- 

 viously reported for certain bacteria. Pyridoxine proved to be a com- 

 ponent of "Factor 11" (287), a concentrate of natural origin previously 

 found essential to growth of T. pyriformis (92). Since pyridoxine inhibits 

 the action of quinine and atebrin against Plasmodium cathemerium and 

 P. lophurne in ducklings (519), the vitamin probably is a requirement of 

 malarial parasites. Among the phytoflagellates, Chilomonas Paramecium 

 synthesizes pyridoxal (207). 



Pantothenic acid. In the first tests on Protozoa, Elliott (1 17) found that 

 growth of T. pyriformis was accelerated, within the pH range 5.5-6.5, by 

 a concentrate of pantothenic acid. Garnjobst, Tatum, and Taylor (139) 

 next found pantothenate essential for Colpoda steinii, and it now appears 

 that Tetrahymerm pyriformis has the same requirement (290, 121). Sup- 

 plementary evidence involves inhibition of growth of T. pyriformis by 

 a-methyl-pantothenic acid and reversal of the efl^ect by pantothenic acid 

 (502). This vitamin also favors survival of P. lophurae (556) in vitro. 

 Furthermore, a pantothenate deficiency in chickens decreases the severity 

 of infections with P. gallinaceum, and dosage with certain analogues is 

 more effective than quinine therapy (28). Pantothenate analogues are 

 active likewise against Trichomonas foetus, T. gallinae, and T. vaginalis 

 in pure cultures (256). Supplementary pantothenate in the diet of rats 

 also increases the populations of Eimeria nieschulzi (15). 



Nicotinic acid. Colpoda steinii (545) was the first protozoan species 

 shown to require nicotinic acid. Later on, Tetrahymena pyriformis, at 

 first believed to grow without nicotinic acid (283), was found to need the 

 vitamin (290). Diphosphopyridine nucleotide (DPN), which contains 

 nicotinamide, also has been demonstrated in T. pyriformis (512). As a 

 component of DPN and TPN, nicotinamide also is involved in oxidative 

 metabolism of Plasmodium gallinaceum (535) and Trypanosoma hippi- 

 cian (194). Among the phytoflagellates, growth of Eugena viridis in an 

 asparagine medium (110) and that of Chilomonas Paramecium as a 

 heteroautotroph (425) are stimulated by nicotinic acid. The latter also 

 synthesizes this vitamine (207, 223). 



Biotin. Although a biotin deficiency has decreased division-rate and 



