Mar. J4. 1919 Ammonification of Manure in Soil 34 1 



Conversion into free nitrogen is the easiest to determine. It has 

 already been seen that fluorescent denitrifiers have been described in the 

 past. Here, they prove to be common enough in soil to be obtained 

 frequently from ordinary soil culture plates. Neither Edson and Car- 

 penter (13) nor Tanner {49) found any among the various cultures they 

 studied; but they both used nitrate broth containing only o.i per cent 

 of peptone, in which appreciable gas production has never been observed 

 here. Most vigorous gas production has been observed in broth or 

 agar containing i per cent of peptone. Typical Ps. fluorescens, how- 

 ever, has never been found to convert nitrate into nitrogen. 



Conversion into ammonia is ordinarily impossible to demonstrate by 

 any simple test, because ammonia can be produced from any nitrogenous 

 substance, and some organic nitrogen is ordinarily present in media. 

 Conversion into nitrite is easy to demonstrate, provided the organism 

 investigated does not convert the nitrite into ammonia or assimilate it 

 as fast as produced. Ps. fluorescens is generally considered to produce 

 nitrite, but Franzen and Lohmann {18) studied two strains of what were 

 presumably Ps. fiiwrescens without obser\dng any action at all on the 

 nitrate. Certain strains of fluorescent Hquefiers have been studied here 

 which produce no appreciable amount of nitrite in media containing 

 peptone or ammonium chlorid, but produce considerable nitrite in 

 an agar containing no nitrogen except potassium nitrate.^ One strain 

 has been found which does not produce nitrite (nor ammonia) even on 

 the latter medium. This suggests that some strains of Ps. flicorescens 

 lack the ability to produce nitrate, wholly or in part, and never attack 

 the nitrate in the presence of more readily available nitrogen. This 

 may explain Franzen and Lohmann's findings (18). 



The question naturally arises whether those organisms that produce no 

 nitrate in ordinary nitrate media constitute a different species from typical 

 Ps. fluorescens. So far as tested, these differences between the strains 

 have proved constant. Nevertheless, the different strains agree in all 

 other particulars investigated, and the data at hand are not considered 

 to warrant the establishment of separate species. As typical Ps. 

 fluorescens is generally considered to produce nitrite in nitrate broth 

 the strain selected for Bright's work in the preceding section was one 

 showing considerable nitrite on all the nitrate media investigated. 



DiASTATic ACTION ON STARCH. — This tcst was made by the method 

 of Allen," streaking the cultures over a plate of agar containing soluble 

 starch, and flooding with iodin after seven days. In general no diges- 

 tion of the starch was observed, although some of the cultures seemed 

 to show a very narrow zone around the growth where the starch had 

 disappeared. 



» The formula of this medium was: Distilled water i.ooo cc, agar is gm.. calcium chlorid (CaClj) 0.5 

 gm. potassium phosphate (K0HPO4) 0.5 gm. . potassium nitrate (KNO2) i gm.. dextrose or sucrose 10 gm. 



5 Allen, Paul W. a simple method for the classification of bacteria as to diastase produc- 

 tion, /n Jour. Bact., V. 3, no. I, p. 15-17. illus. 1918. 



