100 J. T. HOLDEN 
of arginine, lysine, histidine, glutathione and two unidentified compounds!”. Treat- 
ment of this yeast with ultraviolet radiation during nitrogen starvation causes a rapid 
and pronounced replenishment of the pool’. JORDAN has reported that leakage of 
4C-labeled pool components from Rhizobium meliloti is increased by X-radiation. 
Most of these observations are consistent with the general impression that radiation 
damages cellular permeability barriers, although other changes also must occur to 
account for the increases in pool contents observed by HALvorson and by SPOERL 
AND CARLETON. 
The effect of polyploidy has been commented on occasionally and a more detailed 
study of its effects should benefit our understanding of the manner in which intra- 
cellular pools are retained. The study of SARACHEK!® using various Saccharomyces 
strains is notable in this regard. This study showed clearly that per unit dry weight 
of cell the glutamate and aspartate pools were constant regardless of the degree of 
ploidy. Since the dry weight per cell increased regularly with increased ploidy (haploid, 
diploid, triploid and tetraploid), the relative pool size per cell corresponded very 
closely to the degree of ploidy. Unfortunately, the relation between ploidy and cell 
volume and surface area were not described. 
Considerable attention has been focused on changes in pool composition during 
acquisition of antibiotic resistance by microorganisms. GALE AND RODWELL*® ob- 
served that penicillin resistance in Staph. aureus was accompanied by a decline in 
ability to form a large glutamic acid pool during incubation with buffers containing 
this amino acid. MABBITT AND GREGORY"! likewise found a decreased pool size in a 
strain of S. aureus trained to grow in the presence of high concentrations of penicillin. 
On the other hand, naturally resistant strains contained large pools characteristic for 
this organism. GOLDFARB®! also has described changes in the S. aureus pool as penicillin 
resistance was acquired, finding that while alanine, histidine and serine decreased, 
the pool contained increased amounts of valine and glycine. Dress! et al.4? have re- 
ported that acquisition of terramycin resistance by Brucella melitensis is associated 
with the disappearance of valine, methionine, leucine and glutamic acid from the 
pool and a reduction in its content of histidine. 
It should be noted that these studies, while very intriguing, must be appraised with 
caution since acquisition of these new metabolic characteristics 1s frequently accom- 
panied by changes in cell properties which are normally used to establish its identity. 
Thus the danger of selecting contaminants is very high. This emphasizes again the 
value of performing such studies with induced mutants, suitably marked to ensure 
that a derivative of the original strain is being studied. It is possible furthermore, 
in these circumstances, to backcross the new strain as in the study of FUERST AND 
WAGNER*® and thus to establish that the change in pool composition is in fact related 
to the acquisition of the new metabolic property. 
INTRACELLULAR STATE OF THE AMINO ACID POOL 
Despite the large number of reports which describe the composition of pools contained 
within diverse organisms, the question of the location in the cell and the intracellular 
condition of these pools remains a subject of dispute. Indeed in only a few of the studies 
dealing with the occurrence of pools has serious attention been directed to this prob- 
lem. The most perceptive studies instead have come from those investigators con- 
References p. 105/108 
