Jan. 38, 1918 



Nitrogen- A ssimilating Bacteria 



213 



Table XXVI. — Influence of Bacillus radicicola on nitrates in solution giving the quantity 



of nitrogen fixed 



Cul- 

 ture 

 No. 



2 

 3 

 4 

 5 

 6 



7 

 8 



9 

 10 



Treatment (nitrate in 100 c. c. of medium). 



None 



....do 



150 mgm. of NO3 potassium nitrate . . 



....do 



150 mgm. of NO3 sodium nitrate. . . . 



....do 



150 mgm. of NO3 calcium nitrate . . . 



....do 



150 mgm. of NO3 ammonium nitrate . 

 ....do 



Total nitrogen in 100 c. c. of medium. 



Uninoculated. 



Inoculated. 



Found. Average. Found. Average. 



MgTti. 

 2. 40 

 2.50 

 18. 00 

 17.90 

 16.80 

 17. CO 



14. 00 



13.80 



40.50 



41. 20 



Mgm. 



45 



13 



40, 



95 



90 



Mgm. 

 3-3° 

 3-5° 



18. 70 



19. 00 

 19.30 

 19. 20 

 14. 60 

 14. 70 

 41.30 

 41. 70 



Mgm. 

 } 3- 40 



} 18. 8s 



} 19-25 



} 14-65 



\ 41- 50 



Nitro- 

 gen 

 fixed. 



Mgm. 



0-95 



.90 



2-35 

 • 75 

 •65 



The data in Table XXIV show that a rather large reduction in the 

 total nitrate content took place. This reduction varied rather markedly 

 among the four different nitrates studied. The greatest reduction oc- 

 curred where calcium nitrate was used. Potassium and sodium were 

 next in order; the loss was almost the same for both salts. Ammonium 

 nitrate was last with but a very small comparative reduction in total 

 nitrate. 



The question arises as to whether the nitrate is reduced to nitrite, 

 ammonia, or elemental nitrogen or whether the reduction in amount is 

 due to a natural assimilation of the nitrate by the organisms. The first 

 possibility was precluded when qualitative tests for nitrites were made 

 and none found. Table XXV reveals the fact that no ammonia was 

 produced. Table XXVI shows no loss in total nitrogen. Therefore it 

 seems obvious that reduction in total amount of nitrate present is brought 

 about by the assimilation of those compounds by the organisms. 



An inspection of Table XXVI, which gives the results of the total 

 nitrogen determinations, shows that a slight fixation of atmospheric 

 nitrogen took place. This fixation is entirely possible, as will be shown 

 later when the influence of nitrates on the fixation of nitrogen is taken 

 up. In the presence of potassium, sodium, and ammonium nitrates the 

 amount of nitrogen assimilated is somewhat decreased. But in the 

 case of sodium nitrate a large increase in the amount of total nitrogen 

 seems to have taken place. This is interesting in the light of results 

 to be presented later. 



From the results of the work on the effect of B. radicicola on nitrates 

 it may be concluded that the organisms do not reduce the nitrates to 

 nitrite or ammonia or elemental nitrogen under aerobic conditions. 



