FOOD REQUIREMENTS OF NITRIFIERS 221 



More recently, Coleman using pure cultures of nitrate producers 

 obtained ratios varying from 40 to 44. 



Now there are two sources of carbon dioxid which are available 

 to the nitrifying organisms one, the carbonate, which is present 

 in the soil; the other, the carbon, in the air. According to Wino- 

 gradsky, the carbonate supplies the carbon for the bacterial growth, 

 it being liberated by means of the acids, which they produce. On 

 the other hand, Godlewski considered that it is chiefly from the 

 atmosphere that the carbon dioxid requisite for the construction of 

 new cellular substance is derived. He found that development 

 did not occur in cultures containing magnesium carbonate when 

 air free from carbon dioxid was admitted, and concluded that: 

 (1) Nitrosomonas placed in a pure mineral solution are unable to 

 assimilate the carbon of magnesium carbonate; (2) it is very improb- 

 able that the nitrobacter derive their carbon from the organic- 

 substances of the air; (3) it is very probable that these organisms 

 find the carbon which they need in the free carbonic acid or in the 

 carbonic acid of bicarbonates. But Owen, after careful experi- 

 ments in which he used a specially devised flask for the elimination 

 of the carbon dioxid of the air, concluded that "the nitrifying 

 organisms of the soil do not depend to any appreciable extent on 

 the carbon dioxid of the air for their carbon supply." Hence, the 

 evidence seems to be that the organisms under appropriate condi- 

 tions possess the power of utilizing either source of carbon. 



The nitrite bacteria obtain their nitrogen both for oxidation in 

 the production of energy and as building material from ammonia 

 preferably in the form of ammonium carbonate. They are, how- 

 ever, according to Ashby, able to utilize the double ammonium 

 combination formed through the absorption of ammonium salts 

 by modelling clay, but the corresponding combination with peat 

 undergoes no nitrification in the absence of a base. However, 

 according to Marcille, the nitrogen of ammonium phosphate is not 

 so readily transformed into nitrous acid as is that of ammonium 

 sulphate. Yet the phosphate appears to furnish a much more favor- 

 able medium for the transformation of nitrites into nitrates than 

 does the sulphate. 



While calcium cyanamid is nitrified when added to a soil, it is 

 not until it has been transformed into ammonia by other bacteria, 

 chief among which are, according to Lohnis, B. putidum, B. 

 mycoides, B. mdgare var., B. zopfii lepsiense (n.sp.), B. kirchneri 

 (n. sp.), B. megatherium, B.fluorescens, B. subtilis, B. ellenbachensis 

 and B. vulgare. According to Boullanger, the nitrous organism 

 does not attack hydroxylamin hydrochlorid. 



Excessive quantities of ammonia or ammonium salts hinder the 

 multiplication \ of .nitrifying organisms but do not interfere with 

 the action of those already present, Boullanger and Massol found 



