COMPOSITION OF MICROBIAL AMINO ACID POOLS 95 
all nutrients in excess should show changes in levels of individual amino acids. In 
this regard, an investigation of pool composition in synchronously dividing cells 
might be a worthwhile undertaking. 
Among the fungi, growth periods are very much longer than those required to 
culture bacteria, and in many of these organisms sizeable pools can be retained for 
20 and even 30 days!®, 5, 135, 143. RitrER!48 has shown that pools are retained for 
periods even longer than this, although autolytic events contribute to the pool con- 
tents. The two studies on Fusarium again show a markedly different response to 
culture age and as with the bacteria, fluctuation in amount of amino acids predominate 
: a pure Aes 

Figs. 17-22. Free amino acid pool of Strep. faecalis R, grown for varying times in a defined medium 
5 / 5 3) 5 
containing acid hydrolyzed casein. Incubation times were as follows: Fig. 17, 12 h; Fig. 18, 16 h; 
Fig. 19, 22 h; Fig. 20, 39h; Fig. 21, 68 h; Fig. 22, 100 h. Other details as in Figs. 5-10. 
5 5 5 5 , 5 5) 
over qualitative changes in pool composition. The effect of age on the pool in Pen. 
chrysogenum'**; 147 and N. crassa®® has been studied. In the latter organism BARBES- 
GAARD AND WAGNER’ have shown that free phenylalanine and tyrosine decline at the 
onset of protoperithecia formation. In the slime mold, Dictyostelium discoideum, 
KRIVANEK AND KRIVANEK!® showed that the qualitative pattern is a function of 
the stage of differentiation, and WRIGHT AND ANDERSON! observed that the size of 
the methionine pool was a function entirely of the development stage. 
CHEESEMAN AND SILVA*! have observed distinctly different chromatographic 
patterns in some heterofermentative lactobacilli grown at 30° and 37°. In general, 
the effect of varying incubation temperature which would change the division rate 
has seldom been studied. 
References p. 105/108 
