74 J. T. HOLDEN 
disruption and treatment with detergent substances liberated the pool completely. 
Most investigators since then have used boiling water or warm ethanol, although 
cold trichloroacetic and perchloric acids recently have found increasing use. The 
small number of reports encountered in which the comparative effectiveness of different 
extraction procedures was established, suggests that this factor is infrequently in- 
vestigated. HANCOCK"! recently compared nine extraction methods using Staphylococ- 
cus auyveus and found them to liberate essentially equal amounts of amino acids. 
However, small differences in the amounts of individual components can be observed 
in his chromatograms. SPIEGELMAN et al.1”? have verified the efficacy of brief treatment 
with boiling water as a means of liberating unbound glutamic acid from yeast cells. 
However, occasional discrepancies are encountered as in the study of LINDENBERG 
AND MasstNn!" who observed that different amounts of tyrosine are liberated when 
yeast cells are treated with cold trichloroacetic acid and boiling water. ALLEGRA et al.? 
also observed differences in ethanolic and water extracts of Salmonella bareilly. Such 
results suggest that completeness of extraction should not be taken for granted 
especially when a new organism or unusual cultural conditions are used. They also 
bear on the possibility that the pool is not a homogenous entity. 
With few exceptions, microbial pools have been examined by two-dimensional 
paper chromatography. The recognized limitations of one-dimensional chromato- 
graphy have led to its virtual abandonment for examination of the total pool, although 
recent work with the multiple redevelopment technique!” suggests that it may find 
renewed use. Circular chromatography also has been used occasionally, but again the 
relatively uncertain resolution achieved when complex mixtures are examined 
jeopardizes the significance of the observations. Column chromatography, enzymatic 
and microbial methods have been employed relatively infrequently. It must be re- 
cognized that the pool may contain many components at levels below the detectability 
of the ninhydrin reagent and, therefore, may be much more complex than the reports 
summarized here indicate. 
Quantitative estimation of microbial pool components, when attempted at all, 
most often has involved some form of photometric measurement of ninhydrin-spot 
color intensity. In most cases, however, amino acids are reported only as present or 
absent, or on three- or four-step scales of relative amounts arrived at by visual inspec- 
tion of chromatograms. The data in Tables I-XI are presented in one of these three 
systems whichever corresponds most closely to the method used in the original report. 
Quantitative values have all been recalculated when necessary and are given as 
ymoles/100 mg dry cells; semiquantitative systems have been converted to a three- 
step scale (A, AA, AAA); present or absent (usually reported as + or —) are 
indicated by the presence or absence of a filled circle. Examination of a large number 
of tables suggests that the use of geometric symbols more successfully conveys the 
impression of a chromatogram and permits quicker identification of differences 
between organisms. It should be recognized that all such systems are crude approxima- 
tions of the original chromatographic observations and that photographs of original 
chromatographs should be referred to whenever possible. 
With few exceptions, spots on chromatograms have been named on the basis of 
relative position using a map of known amino acids for guidance. The potential 
hazards of this method seem to have been avoided only because the majority of micro- 
bial pools, at least when examined by the paper chromatographic method, appear to 
References p. 105/108 
