284 



The microscopical image during the period of chemosynthesis is that of very 

 small, partly motile rodlets and micrococci. Spore-formers with chemosynthesis 

 do not exist. 



Plate culture. 



The agents of the denitrification with sulfur were isolated on different solid 

 media, but always with the result that the pure cultures, grown on organic media 

 did not, or only feebly denitrify in the anorganic mixture; only those of tJte silicic 

 plates were but slightly enfeebled in this function. The media used were: washed 

 agar dissolved in distilled water, with salts; or tapwater-agar with x /2% thiosul- 

 fate, 0,1% saltpetre and 0,02% bipotassium fosfate; or silicic plates with the same 

 mixture with or without addition of chalk, and finally broth-agar and broth-gelatin. 



If on the media containing organic matter floccules of the sulfur denitri- 

 fication are streaked off and cultivated at 30 C., there appear, already within 

 24 hours, denitrifying colonies which, especially on the broth plates grow with 

 a remarkable rapidity. The two or three chief spezies recognisable among the 

 denitrificators mav be easily distinguished. On the media containing sulfur or 

 thiosulfate and chalk, and on the silicic plates, the colonies remain small and 

 cannot be well recognised on account of the opaqueness of the medium. Yet I 

 have further examined these colonies by making streaks of them on broth-agar 

 plates, always finding that they more or less readily develop; colonies failing in 

 this respekt I did not find. 



I have also tried to obtain anorganic denitrifications with those portions of 

 the streaks on the sulfur- and thio-sulfate plates lying between the colonies, but 

 as well in aerobic as in anaerobic condition always in vain. .^Neither microscopically 

 nor by colouring, bacteria or microbes of other nature could be found in these parts. 



Hence it follows with certainty that the agents of the anorganic denitri- 

 fication grow to colonies both on the sulfur-chalk and the thio-sulfate plates and 

 besides, as will be still further proved below, on the ordinary broth plates. The 

 highly improbable hypothesis that they might be obligative anaerobes is disproved 

 by these experiments, which are, however, well in accordance with the conception 

 that by growth on organic matter their power of autotrophy gets lost. 



To compare the broth with the thiosulfate medium I made the following 

 experiment. 



A platinum wire was bent so as to form at one end a loop, with which 

 droplets of the same size could easily be taken up; the other end was curved 

 to a circular base, which made it possible to place it on the balance and deter- 

 mine the weight of the droplet. Now drops of equal size were taken up with 

 this loop from the anorganic denitrifications and transported for comparison to 

 a thiosulfate- and to a broth-plate. The result was that the number as well as 

 the species of the developing colonies were about the same. All the colonies 

 grown on the thiosulfate plates, after being sown on brothplates, developed very 

 well, quite in accordance with what was observed already for the colonies grown 

 on the sulfur-chalk plates. 



So it is certain that the microbes causing the anorganic denitrification produce 

 colonies on the organic plates. 



