Nitrogen assimilation enzymes in Bacillus subtilis mutants with hyperproduction of riboflavin

Three groups of the nitrogen assimilation cycle enzymes (glutamate synthases (GTS), glutamine synthases (GS), and glutamate dehydrogenases (GD)) were studied in Bacillus subtilis strains with hyperproduction of riboflavin (vitamin B2). It was found that in all strains tested activity of GS was virtually the same, activity of GD was absent, and activity of GTS was reduced. In strains 41 and 24, riboflavin producers, activity of GTS was 30-60% the enzyme activity in the original strain (wild-type RosR). The most pronounced decrease in the activity of GTS (0-12% relative to RosR) was observed in the strain AS5, which had the highest level of biosynthetic activity relative to the other strains. According to the results of determination of the sensitivity of induction of beta-xylosidase to glucose- and fructose-induced catabolic repression, none of the strains studied was characterized by disorders in the protein CcpA, a global regulator of the catabolic repression in gram-positive bacteria, which is required for reducing amination and resulting activation of biosynthesis of glutamic acid in cell. It was suggested that mutations responsible for partial or complete inhibition of GTS biosynthesis caused an increase in the intracellular pool of glutamine. The intracellular pool of glutamine is a nitrogen source for riboflavin in cell. It follows from the results of this work that there is a trend toward an increase in the rate of biosynthesis of vitamin B2 in mutants with inhibited GTS activity. However, the complexity of the processes of regulation of nitrogen assimilation enzymes makes it difficult to find a distinct correlation between GTS activity and riboflavin biosynthesis in these strains.     

Transketolase mutation in riboflavin-synthesizing strains of Bacillus subtilis

Unlike its predecessors B. subtilis rosR and 41, riboflavin producing B. subtilis 24 strain does not utilize pentose and gluconate and poorly assimilates glucose. Simultaneous addition of glutamic and shikimic acid restored its capacity to grow and produce riboflavin in medium with pentose and gluconate. This strain lacks the activity of transketolase, the key enzyme of the pentose phosphate cycle, and possesses normal ribulose-5-phosphate-epimerase and glucose phosphate isomerase activities. Like enterobacteria, B. subtilis has two different transport systems for glucose and mannose. The data are discussed from the viewpoint of increasing riboflavin production by transketolase mutants. Probable consequences of cell wall and cytoplasmatic membrane damage in B. subtilis with this mutation are discussed.     

Analgos of riboflavin, lumiflavin and alloxazine derivatives. II. Effect of roseoflavin on 6,7-dimethyl-8-ribityllumazine and riboflavin synthetase synthesis and growth of Bacillus subtilis]

The replacement of 8-CH3 group in the riboflavin molecule results in the formation of specific antimetabolites. They are rozeoflavin, 7-desmethylrozeoflavin, 8-amino (nor) riboflavin, 8-ribitylamino (nor) riboflavin. Effect of rozeoflavin and other riboflavin analogues on the growth and regulatory characteristics of Bacillus subtilis strains with different genetic state of riboflavin operon is studied. Roseoflavin at a concentration of 0.05 mkg/ml inhibits DRL synthesis in rib-b110 strain. An analogue inhibits the growth of auxotrophic and prototrophic strains at concentrations of 0.5 mkg/ml and 50 mkg/ml respectively. Riboflavin (1 mkg/ml) recovers the growth of bacteria. The curve of rozeoflavin regulation of DRL and riboflavin synthetase synthesis is shifted in 100 times in the direction of lesser concentrations as compared with riboflavin and 8 amino (nor) riboflavin. 180 mutants resistant to 100 mkg/ml of rozeoflavin were selected. 150 mutants over-synthetize riboflavin.     

The bases of epidemiological surveillance for postinjection complications

To carry out the epidemiological analysis of postinjection suppurations and to introduce the relevant prophylactic measures, the forms of registration and account for suppurative inflammatory diseases should be legitimized and the data on such cases per the number of injections made at therapeutic and prophylactic institutions and their branches should be calculated. The organization of centralized sterilization of instruments and the 100% provision of all institutions with these instruments can reduce the occurrence of postinjection suppurations.