The behaviour of Lactobacillus arabinosus towards nicotinic acid and its derivatives

Abstract

L. arabinosus 17-5. which is used in a microbiological assay of nicotinic acid, assimilated this acid from 10-8 or 10-7 [image] solns. during growth. Its cell content of the substance was then 0.7-5 m[mu] mol./mg. dry wt. of cells, according to conditions of growth. The assimilated substance existed in the cells largely as cozymase. Cozymase in L. arabinosus, or added to suspensions of this organism, was much more stable than in the presence of many other bacteria. A slow reaction (of 2-20 [mu][mu] /mol./mg./hr.), leading to inactivation of cozymase and of its nicotinic acid moiety did, however, occur in L. arabinosus during glycolysis. Glycolysis altered also the distribution of nicotinic acid between saline solns. and the cells of the organism, leading to greater retention of the acid in the cells. Rates of glycolysis and of loss in nicotinic acid varied in parallel in suspensions of L. arabinosus, as they had previously been found to do in assay. The ratio between the 2 rates (the catalytic capacity of nicotinic acid) had approx. the same value, of 3-6 x 105, in the 2 cases. The activity of nicotinic acid as a catalyst was much lower in non-proliferating suspensions in simple media, than in assay. Catalytic activity and partial catalytic capacity have been used as measures of the behavior of the organism during assays of the present type.