MALIC ENZYME INDUCTION BY LACTIC ACID BACTERIA: II. PURINE AND PYRIMIDINE REQUIREMENTS

Abstract

Malic enzyme activity was shown to be inducible in cells of Lactobacillus arabinosus, Lactobacillus casei, Lactobacillus delbrueckii, Leuconostoc mesenteroides, and Streptococcus faecalis.Inspection of the nitrogen requirements for induction revealed an obligatory need for purines and uracil by L. casei and L. delbrueckii. Addition of purines and uracil also stimulated induction by S. faecalis and L. arabinosus, but not by L. mesenteroides. The role of purines was inspected further by the inhibitory action of 8-azaguanine.Studies on protein and RNA synthesis during malic enzyme induction revealed that RNA synthesis preceded protein synthesis. This phenomenon was masked in the absence of added purines and uracil by concomitant degradation of cellular RNA. Such breakdown of RNA was observed also when the cells were aged at pH 7.The stimulatory effect of biotin on malic enzyme induction by L. arabinosus could be replaced partially by adenine, and the inhibitory effect of homobiotin was reversed by the addition of this purine. The absence of a biotin effect on induction by L. casei may be related to the requirement for purines and uracil in this organism.