GROWTH STIMULATION OF STREPTOCOCCUS FAECALIS VAR. LIQUEFACIENS BY CANAVANINE.

Hammel, Jay M. (The Pennsylvania State University, University Park) and L. N. Zimmerman. Growth stimulation of Streptococcus faecalis var. liquefaciens by canavanine. J. Bacteriol. 86:490-493. 1963.-l-Canavanine, a competitive inhibitor of arginine, was found to stimulate the growth of Streptococcus faecalis var. liquefaciens in the presence of arginine. This growth stimulation by canavanine was unique, since it previously was found to inhibit the growth of organisms which require arginine. When equimolar concentrations of arginine and canavanine were tested from 10(-7) to 10(-2)m, maximal stimulation occurred at 10(-4)m. Canavanine concentrations of 5 x 10(-6)m to 10(-2)m stimulated growth in the presence of 5 x 10(-5)m arginine. Ornithine similarly stimulated growth. Canavanine inhibited the rate of arginine degradation by the arginine dihydrolase enzyme system in intact cells. It is assumed that the mechanism of canavanine stimulation involves an inhibition of arginine desimidase of the arginine dihydrolase enzyme system, which in turn makes more arginine available for growth over a longer period of time.