588 J. T. HOLDEN 
bacterial pools are accumulated in a free, osmotically active form. Definitive and 
incontrovertible proof, however, has not yet been produced for any microbial system 
and a number of inconsistent observations must be reckoned with. For example, the 
simple interpretation that accumulated amino acids control their own uptake in 
vitamin B,-deficient L. avabinosus by causing an influx of water which distends the 
membrane and causes a premature equilibration of the entry and exit rates is not 
supported by the finding that alanine accumulation, which in normal cells is no 


T lin 
60 
wn 
S' +05 M SUCROSE 
3) 
1o?) 
E 
fe) 
° 
nd 
lu 
% 
= 
res CONTROL 
= 
—_f 
10) 
a) 
xX 
[e) 
— 
= 
1 
60 90 

MINUTES 
Fig. 10. Effect of sucrose on glutamic acid accumulation by biotin-deficient cells of L. avabinosus. 
Incubation at 37° under standard uptake conditions in the absence and presence of 0.5 M/ sucrose. 
higher than the amount of glutamate accumulated by deficient cells, also is only 
30-50% of normal in deficient cells®?. It is not readily apparent why normal alanine 
accumulation of 20 wmoles/100 mg cells is not possible in a B,-deficient cell which 
can accumulate this much glutamate, nor why such cells loaded with glutamate will 
take up a sizable amount of alanine while losing much less than an osmotically 
equivalent amount of glutamic acid. The occurrence of a non-exchangeable pool in 

pemoles GLUTAMATE / 100 mg CELLS 


0 30 60 90 
MINUTES 
Fig. 11. Effect of acetate on glutamic acid accumulation by biotin-deficient cells of L. avabinosus. 
Incubation at 37° under standard uptake conditions in the absence and presence of 0.0057 M 
CH,COOK. 
References p. 592/594 
