COMPOSITION OF MICROBIAL AMINO ACID POOLS 99 
Effects of metabolic inhibitors 
Increases in pool size and accumulation of peptides during exposure to chloramphenicol 
or under conditions which interfere with protein synthesis have been discussed above. 
In contrast, ALLEGRA ef al.3 found that the addition of sub-inhibitory amounts of 
chloramphenicol to growing cultures of Salmonella bareilly had the opposite effect of 
reducing the number of amino acids in the pool. Penicillin causes a marked loss of 
amino acids from bacterial pools 2°. 72, 14,This may occur indirectly by virtue of an 
inhibition of cell-wall formation and the appearance of osmotically labile cells from 
which the pool is readily lost. However, a more specific change in the permeability 
properties of the membrane has not been excluded. In the experiments with Sarcina 
lutea®® proline accounted for all or most of the cellular free amino acid nitrogen lost 
during short exposure to penicillin suggesting a heterogenous loss of pool amino acids. 
Exposure of Verticillium albo-atrum mycelium to to and 30 p.p.m. of the polyene 
antibiotic fungichromin resulted in complete loss of the free amino acid pool! 4, 
However, with 2 p.p.m. there was no inhibition of growth, and a 3-fold increase in 
cellular soluble N including marked increases in the leucines, arginine, lysine and 
proline. LAMPEN e¢ al.!°’, 17 have observed inhibitory effects of another polyene anti- 
fungal agent, nystatin, which may be related to changes in membrane permeability 
in yeast. Streptomycin caused a loss of amino acids from Mycobacterium tuberculosis 
during long exposure periods*®. It is uncertain whether this is related to recent obser- 
vations suggesting an effect of streptomycin on bacterial membranes? or on energy 
metabolism’. In view of the divergent behavior shown by the pool in cells provided 
with or deprived of an energy source one is not surprised to learn that exposure to 
DNP, azide and other agents of this type also produces different effects in different 
organisms. Thus in EF. coli, azide and DNP lowered the pool levels of most amino 
acids and inhibited the increases produced by glucose although not all amino acids in 
the pool responded in the same direction™®. On the other hand, in yeast glucose- 
dependent pool depletion was inhibited by DNP and azide”. 
Heavy metal salts appear to reduce pool sizes. For example, using conidia of Fusa- 
rium decemcellulare, TROGER'? observed that copper and silver salts were especially 
effective in causing the release of amino acids to the suspending medium. Unfortunately, 
a corresponding decline of intraconidial amino acids was not demonstrated. In another 
fungus, Colletotrichum capsict, treatment with copper again reduced the level of most 
pool amino acids!®. The direct cause of these changes has not been established. 
In N. crassa, hydrocortisone appears to raise or lower pool amino acid levels to 
bring them closer to so-called base-line levels®®. On the other hand, deoxycorti- 
costerone has been shown by LESTER ef al.}98.109 to have a marked inhibitory effect 
on amino acid, carbohydrate and inorganic ion uptake by this organism. 
High salt concentrations have been shown by NANI AND GIoLiTTI!*4 to increase 
the pool amino acid levels in B. subtilis. On the other hand, the usually diversified 
yeast pool contained only glutamic and aspartic acids, alanine and histidine when 
cells were grown in the presence of high concentrations of salt}. 
Effects of radiation, polyploidy and antibiotic resistance 
Treatment of S. cerevisiae with a-radiation, X-radiation and triethylenemelanine 
caused a decrease in most pool amino acid levels but a marked increase in the amounts 
References p. 105/108 
