A Relationship Between Cystine and Pyridoxal or Pyridoxamine in the Nutrition of Certain Bacteria

Abstract

Use of pyridoxamine in the medium of Stokes eliminated the requirement of Lactobacillus arabinosus for cystine. Pyridoxal had the same effect, while pyridoxine had little or no effect on growth. Similar results were obtained with Streptococcus faecalis and L. casei. The cystine requirements of L. delbrueckii LD5 and Leuconostoc mesenteroides P-60, however, are not affected by the presence of pyridoxamine or pyridoxal. When incubated at 30[degree]C instead of 37[degree] with 0.4 [gamma]/ml. of pyridoxamine but no cystine, L. arabinosus and L. casei grew slightly, while S. faecalis grew almost equally as well as at 37 [degree]C. To test whether cystine was synthesized from ingredients of the medium, L. arabinosus and S. faecalis were grown 3 days at 37 [degree]C and L. casei 6 days at 37 [degree] in Stokes medium, containing 0.4 [gamma] of pyridoxal/ml., but from which cystine was omitted. The washed cells were acid-hydrolyzed and the hydrolysates assayed by L. mesenteroides P-60. Lactobacillus arabinosus contained 0.38%, L. casei O.65%, and 5. faecalis 0.26%cystine on the basis of dried cells. Whatever the origin of cystine, pyridoxal and pyridoxamine have an essential role in its synthesis in such a medium. Some of the irregularities in the assay of cystine may be explained by the presence of pyridoxal or pyridoxamine in the medium or in samples assayed.