The Availability of Nitrogen Compounds for the Streptococcus.

Abstract

This report deals with the effect upon growth and viability of streptococci, of the addition of various nitrogen compounds to synthetic media. Details of the technique involved have previously been described. 1 , 2 The substances tested include inorganic nitrogen compounds, amino nitrogen compounds, benzene and imidazo derivatives and alkaloids.

We found that (NH₄)₂HPO₄ is more available for streptococcus than (NH₄)₂CO₃, NH₄NO₃ and (NH₄)₂SO₄. Previous investigators make no mention of such findings as applied to streptococcus metabolism. However, Dolt, 3 in his study of about 40 simple media for the growth of B. coli has chosen 2 as the best. One of these contains (NH₄)₂HPO₄ as the sole source of N. Fermi 4 shows that this ammonium salt is easily utilized by B. prodigiosus and B. fitzianus.

The relation of amino acids to the growth of streptococcus is not constant. For example, one series of experiments, in which amino acids were added to a basal mixture, showed glycocoll more beneficial than aspartic acid; in another series of experiments, the same amino acids were added to another basal mixture, aspartic acid was in the lead and glycocoll fell behind. Similar variable effects were obtained between aspartic acid and alanine and glycocoll and alanine. Tyrosine was always less available than glycocoll in these studies. The relation between tyrosine and aspartic acid was not so regular. It is evident that no definite conclusion can be drawn as to the comparative utilization of a certain group of compounds when a single basal mixture is investigated.

When amino acids were compared with other N compounds 2 tendencies were noticed. In some cases the former were utilized less rapidly than the latter. There were, however, comparatively few instances in which this was true.