446 THIAMINE 



for thiamine synthesis. In any event the growth of some plant roots, e.g., 

 tomato roots, or pea roots, is greatly stimulated by extremely small amounts 

 of thiamine (10~^° g. or less per milliliter). Organic manure and fertile soils 

 contain appreciable amounts of thiamine. Experiments under sterile con- 

 ditions have demonstrated that plants are able to synthesize thiamine. 

 Most of it is produced in the young green parts of the plant. In experiments 

 with plants, however, we must take into account the thiamine that is stored 

 in the plants. Bonner^ was able to grow freshly isolated pea roots in a pure 

 synthetic medium containing inorganic salts and sucrose. If such roots were 

 subcultured by the removal of 10-mM. tips into fresh medium and particu- 

 larly if this procedure were repeated several times, thiamine was found to 

 be essential for growth; 0.2 y of thiamine per milliliter of the culture medium 

 gave optimum growth, and even 0.002 7 per milliliter had a marked stimu- 

 lating effect upon the growth of these roots. 



The microorganisms vary considerably in their ability to synthesize thia- 

 mine. Schopfer* established the following groups: 



1. Organisms autotrophic for thiamine: Ahsidia repens. 



2. Organisms requiring only pyrimidine: Rhodotorula rubra type. 



3. Organisms requiring only thiazole: Mucor Ramannianus type. 



4. Organisms requiring both pyrimidine and thiazole: Phycomyces type. 



5. Organisms requiring the entire molecule of thiamine: Glaucoma-Phyto- 

 phthora type. 



6. A separate group of organisms which are partially inhibited by excess 

 thiamine : Rhizopus nigricans and other Rhizopus species. 



Williams et al.^ give a list of those macro- and microorganisms that re- 

 quire either the pyrimidine or the thiazole moiety, those that need both 

 components, and those that do not require any component at all. 



By an (artificial) symbiosis of two microorganisms it is possible to per- 

 form a synthesis of the thiamine molecule, if each organism is able to syn- 

 thesize a different nucleus. 



Schopfer^ gives the examples of Mucor ramannianus and Rhodotorula 

 rubra. When each of these is inoculated separately on a thiamine-free syn- 

 thetic medium, neither is able to develop. But when they are inoculated 

 together, they grow luxuriantly. This proves that Rhodotorula synthesizes 

 thiazole which it supplies to Mucor rammannianus and, conversely that 

 Mucor ramannianus synthesizes pyrimidine which it furnishes to Rhodo- 

 torula. 



3 J. Bonner, Science 85, 163 (1937). 



■* W. H. Schopfor, Plants and Vitamin.s, pp. 110, 114. Chronica Hotanioa Co., Wal- 



than, Mass., 1949. 

 6 R. J. Williams, R. E. Eakin, E. Beerstecher, and W. Shive, The Biochemistry of 



Vitamins, p. 686. Reinhold I'ublishing Corp., Now York, 1950. 



