BIOLOGICAL SOIL PROCESSES 



603 



Some further experiments were carried out with pure cultures 

 of B. mycoides and B. subtilis freshly isolated from the soil. 



Experiment VI. Ammonification in solution by B. mycoides and B. subtilis. 

 Ammonia in milligrams -per 100 grams of solution. 



Dunham solution 



B. mycoides 



B. subtilis 



35.71 

 9.95 



14.37 

 6.07 



These two facultative anaerobes not only live under anaerobic 

 conditions, but carry out their activities as well. Urea bouillon 

 is more easily ammonified than the Dunham solution by these 

 organisms. More ammonia is produced under anaerobic con- 

 ditions with urea and less with peptone. 



In general, from a perusal of the preceding experiments, it 

 appears that ammonification of the substances tested under 

 laboratory conditions, proceeds readily under aerobic or anaero- 

 bic conditions in mass cultures using soil as a medium or in media 

 inoculated with soil or when pure cultures isolated from the soil 

 are used. 



The ammonification of blood meal and casein proceeds as well 

 under anaerobic as under aerobic conditions in the soil. The 

 same is true of ammonification in solutions of urea and peptone. 

 More urea is, however, broken down under anaerobic conditions. 

 Excess air bubbled through inoculated liquid media does not 

 inhibit the production of ammonia, although less ammonia was 

 produced with Dunham's solution under these conditions than 

 under ordinary air conditions. Pure cultures of B. mycoides 

 and B. subtilis readily form ammonia under anaerobic condi- 

 tions. More ammonia is however produced from urea under 

 anaerobic conditions by these organisms. 



