The Assimilation of Amino-acids by Bacteria: 1. The Passage of certain Amino-acids across the Cell wall and their concentration in the internal environment of Streptococcus faecalis

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Abstract
By the use of amino acid decarboxylases the author demonstrated the presence of free lysine, glutamic acid, histidine and ornithine in the internal environment of S. faecalis. Lysine and glutamic acid did not diffuse out when the cells were suspended in saline or distd. water. Growth in deficient media resulted in low internal concs. of these amino acids and such cells were used to study the passage of the amino acids into the cells. Lysine diffuses in freely at its isoelectric point but glutamine or glutamic acid require the presence of glucose, presumably acting as an exergonic source of energy. Both lysine and glutamic acid require the presence of glucose for outward diffusion. The presence of glucose inhibits the uptake of lysine which is partially restored by the addition of glutamic acid to the substrate. Histidine and aspartic acid behave in a similar fashion to glutamic acid.