COMPOSITION OF MICROBIAL AMINO ACID POOLS gI 
absorbing fractions isolated by column chromatography which yielded amino acids 
after acid hydrolysis also contained adenine and guanine in addition to uracil. Besides 
cyst(e)ine, a number of unidentified sulfur-containing compounds were observed in 
hydrolysates®, as well as substances suspected to be amines*!. More recently, JONES 
AND LEwrn® have demonstrated the occurrence of a large number of nucleotide- 
peptides in the green alga, Chlamydomonas moewusit. A variety of nucleotide bases 
were found and the peptide moiety most frequently contained glutamic acid, cystine, 
glycine and serine. 
There also have been some reports that bacteria contain nucleotide-peptides other 
than the uridine and cytidine compounds implicated in cell wall biosynthesis. In 
contrast to the yeast compounds which usually contain uracil, adenine predominates 
in bacterial compounds. BRrown*!, for example, has detected the occurrence in S. 
faecalis of small amounts of adenyl peptides. JONSEN e¢ al.® isolated a chromato- 
graphic fraction from E. coli which yielded adenine, alanine, glutamic acid and glycine 
on hydrolysis. Two nucleotide-containing fractions from B. subtilis also were in- 
vestigated, one of which yielded ten ninhydrin-reactive spots after acid hydrolysis. 
In a separate report this group described the isolation from bacterial cells and spores 
as well as yeast of an unknown which yields amino acids on hydrolysis, contains no 
ribose, but does contain a substance distinguishable from known bases which absorbs 
in the region of 260 mw. 
In summary, there have been a sufficient number of reports from different labora- 
tories to justify the conclusion that a considerable number of nucleotide-peptides 
other than substances concerned in cell wall biosynthesis occur in various classes of 
microorganisms. The metabolic role of these substances remains in the realm of 
speculation although most investigators anticipate a relation to protein synthesis. 
The amounts of amino acid bound in these compounds are small in comparison to 
the apparently uncombined forms considered previously. 
Miscellaneous compounds. AUBERT et al.’ have reported that large quantities of N- 
succinyl-1-glutamic acid occur in Bacillus megaterium during spore formation. This 
substance which comprised up to 8.5 % of the dry weight of the sporulating cell was not 
found in the vegetative cell prior to this stage and, except for traces, also not in the 
formed spore. 
It is likely that careful study of organisms producing some of the newly discovered 
antibiotics having unusual amino acid constituents (see, for example, ref. 158) will 
be found to contain these subunits in an easily extractable form. It also should be 
borne in mind that many metabolically important substances may occur in the pool 
in amounts below the limit of detectability of the ninhydrin-chromatography technique. 
Such substances might be revealed by increasing the sensitivity of the method, for 
example, by using isotopes to label the pool. Examples of this approach can be found 
in the work of the group at the Carnegie Institution? or of DowNEY AND BLACK”. 
The latter provided yeast with °S-labeled methylmercaptan. Cell extracts contained 
nine radioactive substances, none of which was a disulfide and only one a thiol. One 
of these fractions was identified as a stereoisomer of #-methyllanthionine, which on 
desulfuration yielded r-alanine and pD-a-amino-n-butyric acid. 
One of the greatest oversights in the study of microbial pools has been the lack of 
attention paid to the stereoisomeric form of the amino acids detected on chromato- 
References p. 105/108 
