98 J. T. HOLDEN 
depleted pool can be restored rapidly by exposure to inorganic nitrogen or a mixture 
of amino acids. Single amino acids also restore the pool, but affect individual com- 
ponents of the pool differently, an observation reminiscent of the results shown in Table 
XI. Depletion of the pool by nitrogen starvation can be reversed by a brief exposure 
to ultraviolet radiation. MIETTENEN?!*® also has documented changes in the amino 
acid pool of Torulopsis utilis during nitrogen starvation. 
In bacteria, somewhat different observations have been obtained. HOLDEN AND 
Roserts®? demonstrated that incubation of L. avabinosus in phosphate buffers led, 
TABLE XI 
POOL COMPOSITION IN Aspergillus ovyzaé GROWN WITH SINGLE AMINO ACIDS* 
(Adapted from SIMONART AND CHow!*?), 

Pool amino acids 


Amino acid 
in 
growth medium 
Hydroxyproline 
y-Aminobutyric acid 
Valine 
i 
Glutamic acid 
Aspartic acid 
Glutamine 
Glycine 
Serine 
Threonine 
Ornithine 
Arginine 
Citrulline 
Leucine 
Tsoleucine 
Proline 
Alanine 
Aspartic acid 
Alanine 
Serine 
Threonine 
Glycine 
Valine 
Leucine 
Isoleucine 
Proline 
Hydroxy- 
proline 
Arginine 
Citrulline 
Ornithine 

* See footnote * Table I. 
with the exception of alanine and glutamic acid, to rapid loss of the pool unless glucose 
was present. Similarly, MANDELSTAM!!6 observed that nitrogen starvation of E. coli 
carried out in the presence of glucose led to a rise in the pool. In a study on the release 
of amino acids from Streptococcus faecium, CHESBRO AND Evans*® observed only a 
small loss of amino acids from the pool during incubation in buffer at pH 8.5. Deple- 
tion of the pool, however, could be achieved by incubation at pH 10.5, andits replenish- 
ment observed during incubation at pH 9.5 in the presence of glucose. 
In view of the possibility that there may be metabolically distinguishable pools”, 
Cow1e, BritreN, this Symposium) involving endogenously formed amino acids at 
sites or having exchange properties different from amino acids originating exogenously, 
the behavior of pools during such experiments may require re-examination with this 
possible distinction in mind. 
References p. 105/108 
