ESMOND E. SNELL 445 



TABLE 3 

 Some bacteria which require unidentified growth-factors 



Rich 

 Organism Source Material Reference 



Leuconostoc citrovorum Liver extracts Sauberhch and Baumann (28) 



Lactobacillus bulgarictis Yeast WilUams, Hoff-Jorgensen, and 



Snell (42). 



Lactobacillus casei* Yeast, grass Guirard, Snell, and Williams (7) 



Streptococcus faecalis* Yeast, liver McNutt and Snell (22) 



Tetrahymena geleii* Liver, yeast Stokstad, et al. (40) 



(protogen) 



*Cross-testing of concentrates of protogen and of the pyruvate oxidation factor 

 of O'Kane and Gunsalus (23) on these various organisms indicate that these 

 various factors are idendcal (34). 



synthesis, or from inhibition of the synthesis at one or another stage by 

 other metaboUtes normally present within the cell or the medium. The 

 latter occurrence is viewed as being relatively frequent and has been 

 insufficiently emphasized in the past. It permits a ready explanation 

 of the observation that substances such as neopyrithiamine and the 

 sulfonamides, which ordinarily act as growth inhibitors, may with occa- 

 sional organisms simulate the action of true growth factors. It also 

 explains in many cases the fact that a given organism may synthesize a 

 growth factor in one medium and require it preformed in another. 

 The "sparing action" which certain growth factors may have on the 

 requirement of bacteria for other growth factors has also been discussed. 

 Such sparing actions are evidence for a metaboUc relationship between 

 the growth factors involved and are occasionally of such magnitude that 

 the requirement for a specific growth factor may apparently be com- 

 pletely ehminated. Thus in some instances more than a single combina- 

 tion of growth factors may suffice to permit growth of a given organism, 

 although under appropriate conditions each component of each com- 

 bination may be essential for growth. 



REFERENCES 



1. Beadle, G. W., Chem. Rev., 37:15 (1945)- 



2. , and Tatum, E. L., Proc. Natl. Acad. Sci., 27:499 (1941). 



3. , Am. J. Botany, 32:678 (1945)- 



4. Beerstecher, E., Ir. and SmvE, W., /. Biol. Chem., 167:527 (1947). 



5. Boyd, M. I., Logan, M. A., and Tytell, A. A., ibid., 174:1013 (1948) 



6. Broquist, H. p. and Snell, E. E., Unpublished data. 



