Stimulation of Growth of Desulfovibrio desulfuricans 443 



substance when they were contaminated witli certain other 

 microorganisms. These facts suggest that the contaminants sup- 

 plied some factors possessing the growth-stimuhiting activity 

 for Desulfovibrio. 



It was found by Grossman and Postgate (7), and also by 

 Kimata et al. (12, 13) that pure strains of Desulfovibrio desul- 

 furicans could be cultivated without any supplement bearing 

 growth factors when very large inocula were employed. This 

 suggests that the cells added as inocula possibly served as a source 

 of growth-stimulating factors in those cultures. 



In view of these previous works, it may be concluded that 

 factors stimulating the growth of Desulfovibrio are commonly 

 present in various biological matter, including the cells of the 

 organism itself. 



Although attempts to isolate such factors from yeast extract 

 and peptone were made by Postgate (16), a substance possessing 

 the growth-stimulating activity could not be obtained. The 

 factors in yeast extract, however, were found by him to be rela- 

 tively stable to heat, non-volatile, water-soluble, and not removed 

 by various extraction procedures. Postgate (16), and Kimata et 

 al. (12, 13) also tested a number of pure, biologically-active 

 substances including vitamins, amino acids, purines, etc., for 

 ability to replace peptone and yeast extract, in this respect, but 

 they could not find any substance showing such an activity 

 markedly. Although Postgate (16) found, with purified cultures, 

 that cysteine stimulated the growth, and serine, ornithine and 

 isoleucine acted synergistically with it, these amino acids did not 

 account for the whole activity of peptone and yeast extract. 



All these previous studies suggest that the factors in question 

 are substances which have not been regarded as growtli factors 

 for microorganisms, and are expected to be distributed widely in 

 various biological matter. 



ADENOSINE-5 -TRIPHOSPHATE AS GROWTH- 

 STIMULATING FACTOR IN DESULFOVIBRIO 

 DESULFURICANS STRAIN MAIZURU 1 



Based on tlie above presumption, the present autliors (11) 

 tested adenosine-5'-triphosphate (ATP), which is a biologically 



