The Origin of Life 19 



the hydrogen sulphide which is formed as a reduction 

 product from CaS04 or in putrefaction by the activity 

 of certain bacteria can be oxidized by certain grou^DS 

 of bacteria, the sulphur bacteria. Such bacteria, e. g., 

 Beggiatoa, are also commonly found at the outlet of 

 sulphur springs. They utilize the hydrogen sulphide 

 which they oxidize to sulphur and afterwards to 

 sulphates, according to the scheme : 



(i) 2H,S+0,=2H,0+S, 

 (2) S3+30. + 2H,0 = 2H,S04 



The sulphuric acid is at once neutralized by car- 

 bonates. 



Winogradsky assumes that the oxidation of H^S by 

 the sulphur bacteria is the source of energy which plays 

 the same role as the oxidation of NH3 plays in the 

 nitrifying bacteria, or the oxidation of carbon compounds 

 — sugar and others — in the case of the other lower and 

 higher organisms. Winogradsky has made it very 

 probable that sulphur bacteria do not need any organic 

 compounds and that their nutrition may be accom- 

 plished with a purely mineral culture medium, like 

 that of the nitrite bacteria. On the basis of this assump- 

 tion they should also be able to form sugars from the 

 CO 2 of the air. 



Nathanson ^ discovered in the sea water the existence 



^ Nathanson, Mitteil. d. zool. Station, Neapel, 1902. 



