390 



PRINCIPLES OF SOIL MICROBIOLOGY 



in a manner similar to that suggested 13 for plants, whereby formaldehyde 

 is synthesized from C0 2 and gives rise to sugar: 



2 NH 3 + 2 2 = 2 HN0 2 + 2 H 2 

 C0 2 + 2 H 2 = HCOH + H 2 



No oxygen is liberated in this reaction and no carbohydrate from the 

 outside is required. 



It has also been suggested that chemosynthesis takes place in a 

 manner similar to photosynthesis: 



C0 2 + H 2 - HCOH + Oj 



Fig. 16. Apparatus for carbon determination in solution cultures (after Waks- 

 man and Starkey). 



By whatever mechanism the protoplasm is synthesized from C0 2 , 

 energy is required to enable the organism to carry out this work. The 

 energy is obtained from the oxidation of the inorganic substrate, ac- 

 cording to the work of Meyerhof 14 with the nitrate forming organism: 



Nitrogen oxidized (from NOj to NO7), 



mgm 475.0 466.0 385.0 378.0 



Carbon assimilated (from C0 2 ), mgm... 3.52 3.35 2.63 2.95 



N:Cratio 135.0 131.0 146 128.0 



Accordingly, 135 parts of nitrogen are changed from the nitrite to the 

 nitrate form for one part of carbon assimilated from the C0 2 of the 



13 Loew, O. TJeber die Erniihrungsweise des nitrifizierenden Spaltpilzes Nitro- 

 monas. Bot. Centrbl., 46: 222-223. 1891. 



14 Meyerhof, O. Untersuchungen liber den Atmungsvorgang nitrifizierender 

 Bakterien, Pfliig. Arch. Ges. Physiol., 164: 353^27. 1916; 165: 229-284. 

 1916; 166: 240-280. 1917. 



