The Distribution of Amino Acid Decarboxylases in Shigella Dysenteriae

The Significance of Bacterial Enzymes in Ekiri. II

Abstract

The distribution of amino acid decarboxylases was investigated with 10 strains of Sh. dysenteriae. Each strain was inoculated into the meat extract broth (pH. 7. 2) containing 2 per cent glucose, 100^r/ml pyridoxine, and 0.2 per cent amino acid (substrate). After 18-24 hours incubation at37°C the cells were harvested bycentrifugation, washed, resuspended in. the acetic acid buffer solution containing amino acid (substrate) in M/20 concentration, and incubated for 24 hours at 37°C. Thereafter the mixture was treated with alcohol, centrifuged, and the precipitated protein was discarded. One drop of the supernatant was developed on the paperchromatogram and the ninhydrin spots of the amines were examined.
Histidine decarboxylase was demonstrated only in Hanabusa-and Yamadastrains of Sh. dysenteriae I, ornithine only in 1199 strain of Sh. dysenterias I, arginine, lysine and glutamic acid decarbosylases in all strains, whereas tyrosine decarboxylase was found in no strain.
Accordingly, there were only afew among the 10 strains of Sh. dysenteriae, which could decarboxilize histidine and ornithine. None of the 7 strains sent from U. S. A. exhibited the ability of decarboxylizing histidine. This ability was-observed only in 2 strains isolated in Japan.