58 BIOLOGY AND TECHNIQUE 



tivation and composed of silicic acid and inorganic salts have been 

 described by Winogradsky and by Omeliansky. 1 



Other nitrite-forming bacteria have since been described by various 

 observers, all of them more or less limited to definite localities. Some 

 of these are similar to nitrosomonas in that they exhibit the flagellated, 

 actively motile stage. In others this stage is absent. 



The nitrite-forming bacteria, apart from their great agricultural im- 

 portance, claim our attention because of their unique position in rela- 

 tion to the animal and vegetable kingdoms. Extremely sensitive to 

 the presence of organic compounds, they are able to grow and develop 

 only upon media containing nothing but inorganic material; and this 

 entirely without the aid of any substances comparable to the chlorophyll 

 of the green plants. The source of energy from which this particular 

 class of bacteria derive the power of building up organic compounds 

 from simple substances is to some extent a mystery. The carbon 

 which they unquestionably require for the building up of organic mate- 

 rial may be, as Winogradsky believed, derived to a certain extent from 

 ammonium carbonate. But it is also quite certain that they are capable 

 of utilizing directly atmospheric CO 2 . In the absence of chlorophyll 

 or of any highly organized chemical compound, it seems likely that 

 the energy necessary for the utilization of the carbon obtained in this 

 simple form is derived from the oxidation of ammonia during the proc- 

 ess of nitrification. 



The conversion of nitrites into nitrates is carried on by other species 

 of bacteria also discovered by Winogradsky. These bacteria are much 

 more generally distributed than nitrosomonas and probably include a 

 number of varieties. The organism described by Winogradsky is an 

 extremely small bacillus with pointed ends. Capsules have occasionally 

 been made out. It may be cultivated upon aqueous solutions con- 

 taining: 



Sod. nitrite 1 per cent. 



Potass, phosphate 05 " 



Magnesium sulph 03 " 



Sodium carbonate 1 " " 



Ferrous sulphate 04 " " 



The development of the organism is slow and sparse, and is directly 

 inhibited by the presence of organic matter. It is strongly inhibited by 

 the presence of ammonia. 



The Liberation of Energy by Bacteria. Like all other living beings, 



i Omeliansky, Cent. f. Bakt., II, 5, 1899. 



