RIBOFLAVINE 



B. lactis acidi ; ^ Clostridium tetani ; ^ Erysipeloihrix rhusiopathiae and 

 Listerella monocytogenes ; ^ Leuconostoc mesenteroides P. 60 ^ and 

 Streptococcus faecalis R (S. /ad^s R).i^ L. helveticus utilises ribofla vine- 

 phosphate and flavine adenine dinucleotide for growth and acid 

 production equally as well as riboflavine. 



Ribofla vine is utilised by micro-organisms whether they are able 

 to synthesise it or whether they require an exogenous source of the 

 vitamin. H. Mcllwain ^^ estimated that in the five bacteria, Aerohacter 

 aerogenes, Serratia marcescens, Pseudomonas fluorescens , Proteus vulgaris 

 and Clostridium hutylicum between 7200 and 11,000 molecules of ribo- 

 flavine are present in each cell, and that the rate of synthesis ranges 

 from 2 '4 to 11 molecules per cell per second. The " turnover numbers " 

 for fimiaric hydrogenase, D-amino acid oxidase and diaphorase, for 

 each of which flavine-adenine-dinucleotide is the coenzyme, were 22, 

 40 to 50 and 33 molecules per molecule of enzyme per second, that is, 

 between 22 and 50 molecules of substrate react with each molecule 

 of the enzyme per second. The rates of synthesis and inactivation of 

 riboflavine indicate that these reactions are reactions of m/x mol. 

 order in contrast to the ordinary reactions of the bacterial cell, which 

 are of /itml. order. This matter is further discussed on page 284. 



Riboflavine is associated with a possible explanation of the pheno- 

 menon of drug-resistance, that is the ability of certain micro-organisms 

 on repeated exposure to sub-lethal concentrations of a drug to acquire 

 resistance to it. It has been suggested ^^ that the flavoproteins of 

 resistant cells may have become more easily dissociated, due pre- 

 sumably to some alteration in the protein component. It was ob- 

 served, for instance, that Pneumococci which had become resistant to 

 acriflavine or mepacrine readily lost dehydrogenase activity on dilu- 

 tion or warming, and that the activity was restored on addition of 

 riboflavine ; susceptible cells did not exhibit this behaviour. Simi- 

 larly, an extract from resistant cells showed reduced activity when 

 compared with a similar extract from susceptible cells. Riboflavine 

 increased the activity of the former, although the riboflavine contents 

 of both types of cells were approximately the same. 



References to Section 16 



1. P. R. Burkholder, Amer. J. Bot., 1943, 30, 206. 



2. P. R. Burkholder and I. McVeigh, Bull. Torrey Bot. Club, 1943. 70, 



372. 



3. P. R. Burkholder, I. McVeigh and D. Meyer, /. Bad., 1944, 48, 385. 



4. R. C. Thompson, Univ. Texas Publ., 1942, No. 4237, p. 87 ; P. R. 



Burkholder and I. McVeigh, Proc. Nat. Acad. Sci., 1942, 28, 285. 

 4a. H. C. Hou, Proc. Soc. Exp. Biol. Med., 1949, 70, 582. 



5. S. Orla-Jensen, N. C. Otte and A. Snog-Kjaer, Danske Videnskab. 



Selskabs. Skrifter, 1936, 6, No. 5. 

 204 



