XII. 



ADDITIONAL SPECIES OF BACTERIA, NOT 

 CLASSIFIED. 



440. NITROMONAS OF WINOGRADSKY. 



Obtained from the soil at Zurich by Winogradsky (1890), who says: " In 

 speaking of a nitrifying ferment I do not wish to affirm that there is but a 

 single species capable of exercising this function over the whole surface of 

 the globe. That appeal's to me not at all probable. . . . But it is probable 

 that there are but few. At Zurich, for example, up to the present time I 

 have found but a single one." 



Morphology. Ellipsoidal cells, more or less elongated, the youngest 

 cells often nearly spherical; 0.9 to 1 n broad and from 1.1 to 1.8 M long; the 

 longer cells already show the central constriction which precedes binary di- 

 vision; sometimes among the oval cells spindle-shaped cells are seen, and oc- 

 casionally this is the prevailing form. As a rule, the cells do not remain as- 

 sociated after binary division has occurred, but occasionally a chain of three 

 or four elements is seen. Irregular masses are formed in cultures, which are 

 held together loosely by a gelatinous material. 



Biological Characters, Does not grow in the usual culture media, but 

 was cultivated by Winogradsky in a solution containing one gramme of 

 potassium phosphate and one gramme of ammonium sulphate in one thousand 

 grammes of pure water. To this solution he adds half a gramme to a gramme 

 of basic magnesium carbonate. 



In testing the nitrifying power of the ferment the ammonium sulphate is 

 added in separate portions, a standard solution of ten grammes in five hun- 

 dred cubic centimetres of water being used. From two to five cubic centi- 

 metres of this solution are added at intervals of twenty-four to forty-eight 

 hours, according to the rapidity of the ferment action, and the absence of 

 ammonia as a result of this action is determined by the use of Nessler's solu- 

 tion. The cultures are kept at the room temperature. 



The nitromonas of Winogradsky does not form spores. It is sometimes 

 seen to exhibit active movements, but is usually at rest. The researches of 

 the author named show that it is capable of growing and of exercising its 

 ferment action in solutions from which all organic matter has been excluded, 

 and the conclusion is reached that it is able to assimilate the carbon required 

 for its development from the carbonic acid set free in the culture liquid as a 

 result of the action of the nitric acid formed by the nitrifying ferment upon 

 the magnesium carbonate in suspension. 



Recently (1891) Winogradsky has succeeded in cultivating this nitrifying 

 ferment in a solid medium containing soluble silicates, which form a gela- 

 tinous mass (see page 47). The bacillo-cocci of G. and P. F. Frankland 

 appear to be identical with the nitromonas of Winogradsky. The authors 

 named, finding that the nitrifying ferment did not grow in nutrient gelatin, 

 succeeded in isolating it in liquid cultures by the method of dilution. They 

 describe the nitrifying organism obtained by this method as a bacillus which 

 is but little longer than it is broad, and which they designate a " bacillo- 

 coccus." In this country E. O. Jordan and Ellen H. Richards have also 



