MISCELLANEOUS WATER-SOLUBLE GROWTH FACTORS 



Factor HLi was a mixture of Factors HL3 and HL4, but these were 

 certainly different from one another, since they exerted a synergistic 

 action. Another growth factor for L. helveticus and S. lactis R exists 

 in malt-sprouts >" 



F. R. Smith ^ obtained evidence for the existence of a new factor 

 in yeast extract. This was essential for the growth of certain strains 

 of 5. lactis, and could not be replaced by any known vitamin or com- 

 bination of amino acids. The factor was not precipitated by lead, 

 silver, mercury, copper or zinc salts, and was not adsorbed on fuller's 

 earth or activated carbon. It was insoluble in organic solvents and 

 was destroyed by heating to 210° C. under reduced pressure. 



V. H. Cheldelin and T. R. Riggs ^ isolated a factor essential for the 

 growth of L. gayoni 8289 from yeast and liver extracts by adsorption 

 on norit and elution with ammonia. It was amphoteric but apparently 

 not a protein, although it appeared to be combined with a protein in 

 natural materials. 



Metcalf et alJ observed that certain vegetables, particularly 

 tomato juice, contained a growth factor for L. fermentum. The 

 new factor, which could be partially replaced by aneurine, was named 

 the T factor. 



Claims have also been made for the existence of growth factors 

 for Clostridium sporogenes in partially digested proteins ; ® for Lacto- 

 bacillus hulgaricus in yeast ; ^ and for Leuconostoc citrovorum in liver, 

 peptone and yeast extract. ^^ This last factor was distinguished from 

 vitamin B^g ^Y ^^^ ^ ^^^ ^^^^ it ^^^ stable to alkali and did not stimu- 

 late the growth of L. leichmannii. 



The growth requirements of the protozoan, Tetrahymena geleii 

 have been referred to several times before, but in addition to requiring 

 certain recognised B vitamins for growth, this organism also appears 

 to need other factors, termed factor II A or " protogen " and factors 

 IIb ' and IIb ". Some of these may be identical with factors required 

 by L. helveticus and 5. faecalis}^ 



Finally, reference should be made to the fact that many purines 

 and pyrimidines stimulate the growth of micro-organisms, and some 

 of the new factors recently described may ultimately prove to be 

 identical with some of these. Thus factor Z, which promotes the 

 growth of Phycomyces blakesleeanus, is probably identical with hjrpo- 

 xanthine, which is a growth factor for this organism in presence of 

 aneurine. ^2, 13 Hypoxanthine also stimulated the growth of Spirillum 

 serpens, whilst guanine and adenine, although inactive when added 

 separately, together increased the growth of the organism.^* 



Uracil stimulated the growth of S. aureus, ^^ S. pyogenes, ^^ S. 

 salivarius,^'^ certain species of Lactobacillus,^^ Clostridium tetani ^® and 

 Shigella paradysenteriae}^ 



622 



