ENERGY TRANSFORMATION 399 



The organism isolated by Trautwein oxidized thiosulfate without the forma- 

 tion of free sulfur. The results obtained tend to sustain the reaction suggested 

 by Nathanson: 



4 Na 2 S- 3 + 6 2 = 4 Na 2 S 2 6 



3 Na 2 S s 3 + 2§(0 2 ) = Na 2 S 4 6 + 2 Na 2 S0 4 



Sulfate, dithionate and tetrathionate are formed, but no free sulfur and no sul- 

 furic acid. 



In the oxidation of sulfur and reduction of nitrates by Th. denitrificans, the 

 following reactions have been suggested: 



5(S)rh + 6 KN0 3 + 2 H 2 = K 2 S0 4 + 4 KHS0 4 + 3 N £ 



5(S)rh + 6 KNO3 + 2 CaC0 3 = 3 K a S0 4 + 2 CaS0 4 4- 2 C0 2 + 3 N 2 



5 Na 2 S 2 3 + 8 KNO3 + 2NaHC0 3 = 6Na 2 S0 4 4- 4K 2 S0 4 + 2C0 2 4- 4N 2 4- H 2 



3. Sulfur bacteria. These organisms derive their energy primarily from the 

 oxidation of elementary sulfur. They include Th. thiooxidans Waksman and 

 Joffe. The oxidation takes place according to the reaction given above (p. 

 397). One mol of rhombic sulfur will thus liberate 142.2 Cal. Thiosulfate is 

 oxidized by this organism to sulfate and sulfuric acid. 



Thiobacillus thioparus was found to derive its carbon only from the 

 CO2 of the atmosphere or from bicarbonates and carbonates in solu- 

 tion. 28 - 30 Organic materials do not exert any injurious influence, 

 nor stimulate growth, since they cannot take the place of C0 2 . Th. 

 denitrificans is capable also of developing readily on organic media, 

 assimilating organic carbon ; 29 - 31 in other words, this organism is facul- 

 tative autotrophic. On thiosulfate media the carbon is derived either 

 from C0 2 or bicarbonates but not from carbonates. Lieske, 32 how- 

 ever, could not find any injurious or stimulating action due to organic 

 matter, Th. denitrificans deriving its carbon only chemosynthetically. 

 Although small quantities of glucose are used up by Th. thiooxidans, 

 neither the growth of the organism nor the sulfur-carbon ratio 



(sulfur oxidized \ 



7^ : ., , , . : r — ) are appreciably affected. 33 It re- 

 C0 2 assimilated from atmosphere/ 



mains to be found, therefore, in what connection the glucose is used. 



28 Nathanson, 1902 (p. 84). 



29 Beijerinck, 1904 (p. 84). 



30 Jacobsen, 1912 (p. 85). 

 "Trautwein, 1921 (p. 87). 

 82 Lieske, 1912 (p. 86). 



33 Starkey, R. L. Concerning the physiology of Thiobacillus thiooxidans, 

 an autotrophic bacterium oxidizing sulfur under acid conditions. Jour. Bact., 

 135-164, 165-195. 1925. 



