COMPOSITION OF MICROBIAL AMINO ACID POOLS 83 
including homoserine, ornithine, citrulline, ethanolamine, glycerylphosphorylethanol- 
amine and a-aminobutyric acid. Glutathione is present in sizeable amounts in a 
number of yeast pools. It too is infrequently encountered in bacteria although Sor 
AND CERNA!7! and the Carnegie Institution group™® have reported it in EF. colt. In 
addition, MIETTINEN!’ has reported an unknown in Torulopsis utilis which appears 
to contain citrulline and the constituents of glutathione. The values shown for Candida 
utilis were derived from the #C content of chromatographically separated amino 
acids extracted from cells grown on “C-labeled fructose. The amounts of glutamic 
acid, alanine, glycine, the leucines and valine are unusually high in comparison to 
the other organisms. HALVORSON AND SPIEGELMAN’s data were obtained using micro- 
biological assay. No value is reported for glutamine even though it does appear on 
their chromatograms*® since this substance would be measured as glutamic acid. Alanine 
also is not reported. Its universal presence in other yeast strains suggests that this 
is a reflection of the difficulty of measuring this amino acid microbiologically at the 
time these analyses were performed. 
Some of the most comprehensive investigations on the composition and turnover 
of amino acid pools have been carried out with yeast. In addition to the studies of 
Cowlk et al. (cf. ref. 41 and Cowlg, this Symposium) there have been the extensive 
studies of HALVORSON AND SPIEGELMAN ef al.86—70, 172 (see also HALVORSON, this 
Symposium) on various species and strains of Saccharomyces and of MIETTINEN on 
Torulopsis utilis??. As shown in Table VI, these studies have provided much informa- 
tion on the composition of the pool and have served also to demonstrate that the pool 
is utilized as a source of amino acids during protein synthesis. This subject is con- 
sidered in detail in other sections of this volume. 
In addition to the examples cited above, the amino acid pools of the following 
yeasts have been described: Baker’s yeast®; Candida pelliculosa®®; Endomycopsis 
vernalis'4; Saccharomyces ellipsoideus; S. carlsbergensis, S. fragilis, S. chevaliert, 
S. ludwigit, S. cerevisiae, and various other strains”, 172, 
Molds and other fungi 
Representative values for pool amino acids in selected molds are shown in Table VII. 
A number of investigations on Neurospora have been reported, among them the elegant 
study by FUERST AND WAGNER® who examined a large number of biochemical and 
morphological mutants to determine whether consistent differences from the wild- 
type pool pattern could be demonstrated. As a precaution against pool variability 
not specifically associated with the mutation under study all strains which appeared 
to show differences were back-crossed to wild type and the mutant recovered. This 
process was repeated five times with the expectation that the background genetic 
material in wild type and mutant would thereby be substantially similar. Only a 
small number of mutants with distinctly altered pool compositions were encountered. 
Adenine-less mutants lacked leucine or phenylalanine and contained less glycine, 
y-aminobutyric acid and lysine. Methionine mutants contained more threonine and 
glutamine. Although relations could be perceived between such changes and known me- 
tabolic pathways, pool studies did not seem to provide substantial advantages over the 
conventional method of examining culture filtrates of mutants as a means of detecting 
modifications in intracellular metabolism. A total of 35 ninhydrin-reactive substances 
References p. 105/108 
