FACTORS FOR MICRO-ORGANISMS 



growth of micro-organisms. One or two of the factors already dis- 

 cussed, for example, strepogenin (page 6i6) and vitamin B12 (page 

 530), are growth factors for micro-organisms as well as for animals, 

 but there are in addition factors that have been recognised solely by 

 virtue of their action on micro-organisms, and have not yet been 

 tested for growth-promoting activity in animals. 



The exacting organism, Lactobacillus helveticus, has been used by 

 a large number of workers to test for the presence of new factors. 

 Thus, M. A. Pollack and M. Lindner ^ obtained a fraction which was 

 active on this organism and which resembled folic acid in some respects ; 

 it was not very soluble in organic solvents, for instance, and was 

 stable in weakly acidic or alkaline solution but not in presence of 

 strong acid or alkali. It appeared to be amphoteric, however, and 

 was not readily adsorbed from solution and was precipitated by 

 flavianic acid and heavy metals. The activity of this factor was 

 attributed by E. J.-H. Chu and R. J. Williams,^ to the presence of 

 ^-aminobenzoic acid, material with vitamin Bg activity and various 

 amino acids and peptides. 



Other growth factors for L. helveticus were isolated from whole 

 liver by Chattaway et al.^ One, Factor i, was also required for the 

 growth of gravis and intermedius strains of Corynebacterium diphtheriae, 

 and was present in casein hydrolysate as well as in liver. It was not 

 precipitated by saturation with ammonium sulphate ; not extracted 

 from aqueous solution by butyl or amyl alcohol, nor by phenol or 

 ^-cresol ; it gave no precipitate with lead, silver or phosphotungstic 

 acid ; it was not adsorbed on fuller's earth at pYi 3, but was adsorbed 

 on norit at j5)H 3 and eluted by alcoholic ammonia. Another factor, 

 Factor 2, accelerated the initial growth of L. helveticus, and was similar 

 to Pollack and Lindner's factor ; it was partially precipitated by 

 ammonium sulphate and was soluble in butyl alcohol. A third factor. 

 Factor 3, was principally responsible for acid production by L. hel- 

 veticus ; it was soluble in butyl alcohol, phenol and ^-cresol, but not 

 in amyl alcohol, and was precipitated by lead, silver and phospho- 

 tungstic acid. Factor 3 also appears to exist in a combined form, 

 insoluble in organic solvents. A number of synthetic glutamic acid 

 peptides had growth -promoting activity. 



A number of growth factors for L. helveticus were isolated from 

 liver by Barton-Wright et al* in the course of attempts to prepare a 

 concentrate of folic acid. Various fractions were obtained that 

 stimulated the growth of L. helveticus and 5. lactis R ; these differed 

 from folic acid in being soluble in chloroform. Two, designated 

 Factors HLi and HL3, were adsorbed on Decalso, but differed from 

 one another in their growth promoting activity, whilst the third 

 Factor HL4, was not adsorbed on Decalso. It was possible that 



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