g6 J. T. HOLDEN 
Effect of growth-medium composition 
Most investigations in which this question was considered have dealt with changes 
in the pool produced when the source of carbon and/or nitrogen is modified (e.g., 
refs. 14, 55, 56, 62, 70, 82, 88, 90, 91, 139, 162, 163, 164, 178, 181, 195). Invariably, 
pools are found to be larger and more diversified when the growth medium is supple- 
mented with a mixture of amino acids in place of an inorganic-nitrogen source. Gener- 
ally, these larger pools are retained during thorough washing procedures and most 
likely are formed by the operation of metabolically dependent amino acid accumu- 
re U2 
ie 

25 28 | “di 
YF af 
Figs. 23-28. Effect of a severe vitamin B, deficiency on the amino acid pool of. L. avabinosis 17-5, 
Figs. 23, 24 and 25 show the pool in control cells grown in a synthetic complete medium for 16, 
38 and 62h, respectively. The compound indicated in Fig. 24 is y-aminobutyric acid. Figs. 26, 27 
and 28 show the pool in cells grown for 16, 38 and 62h, respectively, in a medium from which 
vitamin B, was omitted. Maximum growth in the deficient culture was 20% of that achieved by the 
control culture and equal dry weights of cells were extracted for chromatography. U,, U, and U, 
indicate unidentified substances. Chromatography as described in Figs. 5-10. 
References p. 105/108 
