1215 



The very striking fact, that the nitrate ferment acts best when 

 organic substances are as far as possible kept out of the cultures, 

 has suggested the supposition that this raiicrobe could feed by 

 chemosynthesis, whereby the energy, produced by the oxidation of 

 the nitrites should serve for the reduction of atmospheric carbonic acid. 



For this hypothesis I hav^e not, however, been able to find a 

 single proof. 



When the pure nitrate ferment is cultivated in a liquid tiiis remains 

 quite clear; only with the microscope many bacteria can be detected, 

 especially on the glass wall. A particle of cotton wool fallen from 

 the air into the cultures, represents a quantity of organic matter 

 equalling some millions of nitrate bacteria. 



On silica plates soaked with solutions of 0,17o to 0,05°/^ sodium 

 nitrite and 1,0J "/o bipotassium fosfate, the nitrate ferment always forms 

 small but very active colonies only visible when magnified and the 

 smaller as the organic matter is better removed from the plates. So 

 there is also here ground to suppose that for the carbon requirement 

 of these extremely small colonies, always a sufficient amount of organic 

 substance is present in the impurities of the plates. 



But the strongest argument against the existence of chemosynthesis 

 with regard to the nitrate ferment, is the following circumstance. 



The crude cultures are always covered in the laboratory with a 

 thin, floating film, consisting of the above mentioned highly remark- 

 able bacterium, described by me in 1903 under the name of 5/7ce7/w.9 

 olifjocarbophilus ^) When the nitratation experiments are effected in 

 a hothouse this film also appears but later and tiien it ahvays remains 

 much thinner. When such nitratations are sown out on agar- or silica- 

 plates, Bacillus' oligocarhophilus likewise forms colonies, which at 

 first sight reveal their relation to the nitrate ferment, but they grow 

 out considerably larger and finally have the appearance of snow- 

 white, dry, flat plates of one or more millimeters in diameter. As 

 B. oligocarbophilus is not able to oxidise nitrites, and hence, under 

 the said circumstances does certainly not possess the |)Ower of re- 

 ducing carbonic acid by chemosynthesis, there must evidently be 

 in the environment a sufficient amount of fixed organic carbon to 

 provide the carbon requirement of this species. As the nitrate ferment 

 not only lives in the same fluids as B. oligocarbophilus, but by the 

 nature of the colonies resembles it very much, and moreover quite 

 corresponds with it as regards its microscopic appearance, its motility 



1) Farblose Bakteriën deren Kohlenstofl' aus der atmosferischen Luft herriihrt. 

 Centralbl. fur Bakteriologie, 2e Abt. Bd. 10. S. 38. 1903. 



79 

 Proceedings Royal Acad. Amsterdam. Vol. XVI. 



