Abstract
When growth inhibition test of Leuconostoc mesenteroides P-60 in medium containing DL-alanine and limited amounts of vitamin B_6 was carried out with a series of concentration of vitamin B_6 antagonist, e. g. 2-methyl-4-amino-5-hydroxymethylpyrimidine (OMP), the growth-OMP curve showed a characteristic phenomenon which had double reflections. The ratio of OMP to different types of vitamin B_6 at the first refletion was highest when pyridoxal was used, followed by pyridoxal phosphate, pyridoxamine, and pyridoxine. The order was accordant with thet of vitamin B_6 activity to Leuc. mesenteroides. Growth of Streptococcus faecalis R was inhibited by OMP in the medium containing limited amounts of vitamin B_6 and without having DL-alanine. Potency to overcome the inhibition was order of pyridoxamine> pyridoxal phosphate> pyridoxal. The order was not same as that of vitamin B_6 activity (pyridoxamine>pyridoxal>pyridoxal phosphate) to Stc. faecalis.
