COMPOSITION OF MICROBIAL AMINO ACID POOLS 79 
which frequently contain asparagine, pools in gram-negative bacteria appear not to 
contain this amino acid. Glutamine and tryptophane also are seldom reported. Despite 
their interesting nutritional requirements, little work on the autotrophic bacteria has 
been reported. Although the findings of MUKHERJEE!® (Table II) indicate a very 
limited pool, judgement should be reserved until a more extensive study is presented 
including at least an examination of the effect of culture age and washing procedures. 
Interestingly, the algae, with a comparable ability to synthesize nutrients, contain a 
large and varied pool of amino acids®*: 187, MUKHERJEE’s report is of interest also 
because y-aminobutyric acid and taurine appeared when the extracted cell residue was 
hydrolyzed, suggesting the occurrence of bound forms of these substances. On the 
other hand, such hydrolysates did not contain glutamic acid, threonine, the leucines, 
lysine, arginine or histidine indicating a unique protein composition. 
SKARZYNSKI AND OSTROWSKI!® have reported the occurrence of a variety of sulfur 
compounds (cysteine, cystine, methionine, cysteic acid, cysteine sulfinic acid and 
TABLE III 
COMPARISON OF TOTAL AMINO ACID POOL IN GRAM-POSITIVE AND -NEGATIVE BACTERIA 




Total Pool 
Organism (umoles/Too mg Ref. numbers 
dry wt.) 
Staphylococcus aureus 28 7 sbnag {fs} 
Bacillus subtilis 35 142 
Bacillus subtilis 30-85 I15 
Escherichia coli 2-5 116 
Staphylococcus aureus (+ chloramphenicol) 7O 7B 
Escherichia coli (+ chloramphenicol) II 116 



a-thiooctanoic acid) in ethanolic extracts of Thiobacillus thioparus. In this case, whole- 
cell hydrolysates contained a typical mixture of protein amino acids. [his group 
also has reported the interesting finding that this organism utilizes only the outer 
sulfur atom of thiosulfate leaving the inner sulfur atom in the medium as sulfate!®, 170, 
Amino acid pools in the following gram-negative bacteria also have been described: 
Aerobacter sp.1®§; Agrobacterium tumefaciens®; E. cola; Pseud. hydrophila*®; Pseud. 
savastanoi® ; Pseud. sp. 7; Rhizobium meliloti; Vibrio cholera}. 
Despite the uncertainty and controversy concerning the occurrence and size of 
amino acid pools in gram-negative bacteria, only a few reliable quantitative studies 
have been reported. Table II] summarizes some values for gram-positive and -negative 
bacteria. The pool in freshly harvested cells of EF. coli is about one tenth as large as the 
pools in gram-positive organisms. In both types, incubation in the presence of chloram- 
phenicol causes a sizeable increase in pool size, but the E. coli pool is still relatively 
smaller. When incubated with a single amino acid many organisms have been observed 
to accumulate large amounts of this amino acid intracellularly. These intracellular 
levels also can be used as an index of the pool capacity. Results of representative 
studies are summarized in Table IV. Under these circumstances gram-positive bacteria 
accumulate single amino acids in amounts corresponding to total pool levels observed 
in freshly harvested cells (Table III). E. coli has been observed to accumulate moderate 
References p. 105/108 
