AMINO ACID TRANSPORT IN MICROORGANISMS 585 
clear association of improvement in accumulation capacity and increase in cell wall 
mass, this might be a coincidental relationship and not of a causal nature. Therefore, 
the fate of {!4C]acetate was investigated under pretreatment conditions®!. As shown 
in Table V, this substance is incorporated principally in two cell fractions, the ethanol- 
soluble and the cell wall fraction. In vitamin B,-deficient cells the incorporation of 
label in the cell wall is specifically reduced. In the presence of ammonium ion, 
vitamin B, and glutamate this incorporation is increased to levels observed in control 
B,-adequate cells (Table VI), without modifying the incorporation of acetate into 
other cell fractions. In other words, those conditions required for a substantial im- 
provement in accumulation activity are identical with those required for normal 
entry of acetate into cell wall material, and of all the cell fractions the wall specifically 
shows this effect. It can be concluded with greater confidence, therefore, that an 
increase in cell wall substance in vitamin B,-deficient cells leads to a restoration of 
nearly normal accumulation activity. 

Fig. 8(b). For legend see page 584. 
References p. 592/594 
