THE NITROGEN CYCLE 



231 



COOH + 2HN0 2 = COOH + 2N 3 + 2H 2 



CHNH 3 



CH, 



CONH 2 



Asparagin 



CHOH 



CH 2 



COOH 



MaHc acid 



Recently a somewhat sensational discovery has been 

 made by Beyerinck and Minkman. Besides identifying the 

 de-nitrifying organism originally discovered by Gayon and 

 Dupetit, they have isolated two other organisms, which are 

 probably the destroyers of nitrates in the soil. They describe 

 the following experiment : 



A bottle, with a well-fitting glass stopper, is filled with 

 bouillon, containing 8 per cent, of potassium nitrate, and 

 10 to 20 grams of garden soil are added. After incubation 

 at 37 C. for a day or two, a considerable froth forms, 

 which forces out the liquid by a capillary action between the 

 stopper and the neck of the bottle. The gas evolved remains 

 in the bottle, and on cautiously opening the bottle at the 

 end of forty-eight hours, and applying a glowing chip, it will 

 burst into flame through the action of the nitrous oxide 

 present. This has been found to amount to as much as 

 90 per cent, of the gases evolved. They have also isolated 

 a second organism, which is capable of causing the com- 

 bination of hydrogen and nitrous oxide, when these two gases 

 are simultaneously led into the solution containing the 

 organism. From this combination the organism appears to 

 derive energy which enables it actually to decompose carbon 

 dioxide, and thus utilise the carbon for building up its own 

 structure. This is an extremely interesting instance of the 

 reabsorption of carbon from its final state of oxidation as 

 carbon dioxide, back into the cycle of organic life. We know, 



