73 
III. MICROORGANISMS 
THE COMPOSITION OF MICROBIAL AMINO ACID POOLS 
JOSEPH T. HOLDEN 
Department of Biochemistry, Medical Research Institute, City of Hope Medical Center, 
Duarte, Calif. (U.S.A.) 
This review summarizes a representative sample of the available information con- 
cerning the composition of amino acid pools in bacteria, yeasts, molds and other fungi. 
Most of the reports cited concern studies in which the primary intention was a des- 
cription of the complete pool or a major part of it. Reports on individual components 
are less frequently included, usually only when a substance of uncommon structure 
or function is described. Studies on pool turnover, active transport, protein synthesis, 
etc., occasionally include descriptions of pool contents. Such information, when en- 
countered, has been included unless extensive duplication in other sections of this 
volume could be anticipated. 
From a historical viewpoint the first clear indication that microorganisms contain 
a diverse collection of apparently free amino acids must be credited to ERNEST GALE 
et al.>4, 56, 57, 178. Using amino acid decarboxylases as an analytical tool, his group 
demonstrated that various bacteria and yeast contain large amounts of readily extract- 
able amino acids. Rorne!!, 52, 153 simultaneously reported the occurrence in yeast of 
non-protein amino nitrogen compounds and while he identified alanine, glutamic 
acid and glutamine, the classical methods of isolation and identification used precluded 
a complete description of the pool. The work of GALE AND TayLor also provided an 
incomplete description of the pool since the amino acid decarboxylases used for 
quantitative analysis restricted their study to those amino acids which were substrates 
for these enzymes. The presence of a varied pool, however, was clearly apparent, and 
the development and widespread application of paper chromatographic methods 
which occurred at this time made possible the more complete studies which will be 
considered here. 
Prior to this time, there had been little work done on microbial amino acid compo- 
sition and such studies were concerned entirely with the composition of cell hydro- 
lysates??, 175. The development of microbiological assay methods for the amino acids 
provided a convenient tool for such studies, but its extension to studies of the freely 
extractable pool did not occur until later and it was some time before the assay or- 
ganisms themselves were subjected to analysis. 
DESCRIPTION OF POOL CONTENTS 
Examples of the available information concerning amino acid pool composition will 
be found in Tables I-XI. A number of general comments are required in view of the 
divergent techniques, organisms and objectives encountered in these studies. 
A number of extraction procedures have been used to liberate pools from microbial 
cells. GALE®* and GALE AND TAYLOR* originally found that boiling water, mechanical 
References p. 105/108 
