Chapter 41 



Organic Factors Responsible for the 



Stimulation of Growth of 



Desulfovibrio desulfuricans 



Hajime Kadota and Hideo Miyoshi 



A he present paper describes in outline some recent experi- 

 ments on the nutritional requirement of Desulfovibrio desulfuri- 

 cans already reported by us (11), and presents some fresh in- 

 sight into the roles of growth stimulating factors in the metabo- 

 lism of this microorganism. 



It has already been found by many workers that the growth 

 of sulfate-reducing bacteria was more or less stimulated by 

 certain factors contained in natural organic substances of in- 

 definite composition. Since the work of Bunker (4), who showed 

 that yeast, yeast water, and filtered yeast culture stimulated 

 the growth of Desiilfovihrio desulfuricans, more than ten papers 

 (1, 6, 7, 10, 12, 13, 14, 16, 17, 18, 19, 23) have been published on 

 the presence of such stimulating factors in peptone, yeast extract, 

 liver extract, beef extract, potato juice, protein hydrolysates, milk 

 and other natural substances. Although several workers (2, 5, 6, 

 20, 21, 22, 24) reported that Desulfovibrio grew autotrophically 

 in simple mineral media without organic nuti'ients, the apparent 

 growth observed by these authors was attributed recently by 

 Mechalas and Rittenberg ( 14 ) , and by Postgate ( 19 ) to the utili- 

 zation of organic substances present as impurities in the auto- 

 trophic media. Such organic impurities might serve not only as 

 hydrogen donors in energy-yielding reaction but also as growth 

 stimulants for these bacteria. 



Some of the previous works (12, 13, 26) also indicated that 

 these bacteria could easily be cultivated without added natural 



442 



