710 



ADDITIONAL SPECIES OF 



succeeded in isolating a nitrifying ferment by the method of dilution and by 

 cultivation in a liquid containing certain salts dissolved in distilled water. 

 Their culture medium was constituted as follows : 



Ammonium chloride (resublimed) , 

 Sodium carbonate, 

 Sodium phosphate, . . . 



Potassium sulphate, 



1.9070 grammes. 

 3.7842 



0.2000 " 

 0.2000 " 



" These salts were dissolved in such a quantity of redistilled water that the 

 solution contained one hundred parts of nitrogen per one hundred thousand, 

 and two equivalents of alkali. Ten cubic centimetres of this solution were 

 mixed with one litre of redistilled water and then inoculated as desired . " 



The nitrifying ferment obtained by Jordan and Eichards is described as a 

 short bacillus of a slightly oval shape, about 8 to 9 M broad and from 1.1 to 

 1.7 u long. These bacilli are associated in irregular zooglcea by a jelly-like 

 material. The masses are found chiefly at the bottom of the flasks, as was 

 the case with the nitrifying ferment isolated by Winogradsky. No inde- 

 pendent movements were observed by Jordan and Richards, who state that 

 they have not been able to determine in a definite manner whether the nitri- 

 fying organism isolated by them is identical with that of Winogradsky and 

 of the Franklands. They remark that their bacillus stains with some diffi- 

 culty with the usual aniline dyes. 



441. NITRIFYING BACILLUS OF WINOGRADSKY. 



Obtained by Winogradsky (1891) from the soil by cultivation in a gela- 

 tinous medium containing soluble silicates. 



Morphology. Small bacilli of somewhat irregular form, often pyriform ; 



the average length does not usually exceed 

 0.5 /u, and the breadth is quite variable, 

 even in the same cell. The bacilli are 

 grouped in irregular masses and united 

 into a membranous pellicle by a gelatin- 

 ous material. This pellicle in old cultures 

 is seen attached to the bottom of the tube 

 as a transparent membrane, which may be 

 detached by agitation ; in more recent 

 cultures it is firmly adherent and sa 

 transparent as to be seen with difficulty ; 

 it gives to the glass a feeble bluish-gray 

 tint, and is not detached by repeatedly 

 rinsing the tube with distilled water. The 

 bacilli are somewhat difficult to recognize 

 in stained preparations, owing to the stain- 

 ing of the gelatinous intercellular sub- 

 stance. Winogradsky recommends wash- 

 ing the stained preparation with water at 

 50 to 60 C. to remove the color from the 

 gelatinous material. 

 The Biological Charactersof this bacillus have not been fully determined. 

 In a gelatinous medium made by the addition of silicic acid to a culture liquid 

 containing certain salts, yellowish-gray, lenticular colonies were developed, 

 from which liquid cultures were subsequently made by Winogradsky. In 

 these the liquid remained transparent, and no pellicle formed upon the sur- 

 face, but a very transparent, gelatinous film was found attached to the bot- 

 tom of the flask ; the bacillus above described was found to be present in this 

 and to be the cause of the active oxidation of nitrites present in the culture 

 medium. With reference to its ferment action Winogradsky says: "The 

 oxidizing power of this imponderable quantity of a living ferment is aston- 

 ishing. " When this bacillus is associated with the microorganism previously 



Fin. 258. Nitrifying bacillus of Wino- 

 gradsky. x 1,000. From a photomicro- 

 graph. (VVinogradsky.) 



