SCIENTIFIC PROCEEDINGS 



One hundred ninth meeting. 



Abstracts of Communications. 



Cornell University Medical College, October 17, IQ20. 

 President Calkins in the chair. 



1 (1583) 



The oxidation of sulfur by microorganisms. 



By Selman A. Waksman and J. S. Joffe. 



[From the New Jersey Agricultural Experiment Station, New 

 Brunswick, N. J.] 



Two groups of phenomena are to be considered in the study of 

 the sulfur cycle: (1) the reduction phenomena and (2) the oxi- 

 dation phenomena. The first result in the production of hydrogen 

 sulfide and the second in the oxidation of H 2 S to S and of the 

 latter to H2SO4. Both groups of phenomena result from activities 

 of microorganisms. Winogradsky was the first investigator to 

 have definitely demonstrated the role of microbes in the oxidation 

 of the H 2 S to S, and of the latter to H 2 S0 4 , but it is characteristic 

 that the organisms studied by Winogradsky (Beggiatoa and 

 Thiothrix), never turned the medium acid: this was explained by 

 the presence of sufficient CaCC>3 in the culture to neutralize 

 any acid formed. Keil isolated the two organisms in pure culture 

 only about thirty years after the work of Winogradsky was 

 carried out. 



The sulfur oxidizing bacteria were usually divided into four 

 groups, namely (1) Thread-forming colorless bacteria, accumulat- 

 ing sulfur within their cells. The Beggiatoa and Thiothrix are 

 representative of this group. (2) Non-thread forming, colorless 

 bacteria, accumulating sulfur within their cells. Here are referred 

 forms (Thioploca, Thiovulum etc.) of various sizes and shapes, 



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