TRANSFORMATION OF SULFUR 



G13 



are quantitative rather than qualitative in nature; 32 they are largely 

 determined by the nature of the medium and oxygen tension. Ac- 

 cording to Rubner, 33 Bad. vulgare formed 33 mgm. of H 2 S under 

 anaerobic conditions, and only 4 to 5 mgm. under aerobic conditions 

 in one liter of peptone-free bouillon. Quantitatively, the H 2 S is de- 

 termined by the difference in the total sulfur content of the medium. 34 

 The gases formed may be absorbed in standard iodine solution from 

 which the sulfide is determined by titration with thiosulfate. When 

 organic sulfur compounds are decomposed by the agency of micro- 

 organisms, most of the sulfur may be assimilated and resynthesized, 

 as shown by Rubner for Bad. vulgare grown in a liter of bouillon: 



The loss of 5.2 mgm. is due to the formation of H 2 S, while the larger 

 portion of the organic sulfur is transformed into microbial protoplasm. 

 When proteins and other sulfur bearing organic materials are added 

 to the soil they are hydrolized by the activities of microorganisms into 

 the various constituent groups and the sulfur-bearing amino acid, cys- 

 tine or di- cystine, or di-jS-thio-a-amino- propionic acid liberated. 



S— S— CH 2 



I 

 CH • NH 2 



CH 



I 

 NH 2 • HC 



HOOC COOH 



Cystine 



32 A detailed study of the organisms concerned in the formation of H 2 S from 

 various sulfur compounds is recorded by Sasaki, T., and Otsuka, I. Experi- 

 mented Untersuchungen fiber die Schwefelwasserstoffentwicklung der Bakterien 

 aus Cystin und sonstigen Schwefelverbindungen. Biochem. Ztschr., 39: 208- 

 215. 1912; Myers, J. T. The production of hydrogen sulfide by bacteria. Jour. 

 Bact., 5: 231-252. 1920. 



33 Rubner, M. Die Wandlungen des Schwefels im Stoffwechsel. Arch. Hyg. 

 16: 78-100. 1893. 



34 See Almy, L. H. A method for the estimation of hydrogen sulfide in pro- 

 teinaceous food products. Jour. Amer. Chem. Soc, 47: 1381-1390. 1925. 



