755 



inoculated with the bacteria ammonia was oxidized rapidly. The infer- 

 ence is that the bacteria are tlie nitrifying" organisms of the soil. 



Winogradsky describes the organism as of oval form, about 1.1-1.8// 

 long and 0.9-1 (i wide, usually at rest, but capable of motion at times, 

 and dividing perpendicularly to the longest axis. He places it in a 

 genus by itself, which he calls Nitromonas. Whether only one single 

 form of nitrifying bacteria exists or whether there are other forms, Win- 

 ogradsky does not attempt to say at present. The soil about Zurich 

 gave only this one form, and a sample of soil from a distant locality 

 gave bacteria in every way resembling it. But he is inclined to believe 

 there may be several species and chooses to refer to them not as a single 

 ferment but as a physiological group whose special function is the 

 oxidation of ammonia; and having designated those which cause the 

 oxidation of sulphur and iron compounds as sulphobacteria and ferro- 

 bacteria he applies to these the term nitro-bacteria. 



By way of comparing the nitrifying activity of the nitromonas with 

 that of the nitrifying ferments as they may actually occur in the soil, 

 Winogradsky made a series of experiments to compare the amount of 

 nitrification in his culture liquid with that observed by iSchlosing in a 

 soil to which^ however, more oxygen had access than was the case with 

 Winogradsky's liquid. 



While in Schlosing's experiments by the use of 200 grams of earth, 

 3.4, 9, and 4.1 mg. of nitrogen, respectively, were nitrified, Wino- 

 gradsky's pure cultures of bacteria nitrified 8G0 mg. of ammonium 

 sulphate in 37 days and 930 mg. in 30 days, which in the period at 

 which the nitrification was most energetic would furnish about 7.2 mg. 

 of nitrogen per day. 



Winogradsky further investigated the interesting and very remark- 

 able fact previously cited, that the nitromonas, although it contains no 

 chlorophyll, grows and is able to multiply in a solution entirely free 

 from orga nic matter. To prove this fact beyond doubt he prepared a cul- 

 ture medium absolutely free from every trace of organic matter by using 

 water distilled twice and tested, and salts which had been carefully puri- 

 fied by recrystallizatiou. He thoroughly removed all organic matter 

 from the glass dishes and apparatus to be used, and inoculated sepa- 

 rate portions of the medium with the nitromonas. All of the cultures 

 developed normally, and in the dark as well as in the light. To gain 

 an idea of the extent of the assimilation of carbon the carbon in the 

 organic matter which had been formed by the organism in its growth 

 was determined by analysis. Four cultures contained respectively, 

 10.2, 7.1, 4.6, and 4.8 mg. of assimilated carbon ; and in these cultures, 

 respectively, 928, 604, and 83.5 mg. of nitric acid had been formed. 

 This seemed to leave no doubt that nitromonas is able to assimilate 

 the carbon of carbonic acid. 



The oxidation of ammonium salts by nitromonas, according to Wino- 

 gradsky, takes place only in the presence of atmospheric oxygen j the 



