902 
Wotrr-Dreenrer,’) by oxydation with bichromate and sulfuric acid. 
After a culture of about six weeks there was in this way found 
about 0.05 gram of carbonic acid per gram of oxidised sulfur, which 
corresponds to 0.013 gr. of organic carbon.’) This quantity, however, 
must certainly be donbled, for at the extraction of the chalk and 
sulfur at least half the weight of the bacterial substance is lost. I 
therefore esteem the production of organic carbon in relation to the 
oxidised sulfur at 2°/, in weight. 
Old cultures containing much organic matter and in which the 
nitrate has disappeared produce H,S, obviously in consequence of 
sulfate reduction, and perhaps, too, directly from the still present 
sulfur, whilst the hydrogen wanted for this originates from the 
organic material formed by chemosynthesis. Such liquids finally teem 
with infusoria and monads, and various other members of the so 
remarkable ‘“sulfur-flora” and ‘-fauna’’. 
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 an- 
organic mixture; only those of the 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 */, °/, 
thiosulfate, 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 floceules of the sulfur 
denitrification 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 species recognisable among the denitrificators may be easily 
distinguished. On the media containing sulfur or thiosulfate 
and chalk, and on the silicic plates, the colonies remain small 
1) F. TrEMANN und A. GäRrTNER. Die chemische, mikroskop. und bakteriol. 
Untersuchungen des Wassers. 3te Aufl. Pag. 247, 1889. 
8) The quantity found by Mr. JACOBSEN at the direct oxidation of sulfur by 
bacteria was of the same order. (Die Oxydation des elementaren Schwefels durch 
Bakterién. Folia Microbiol. Jahrg. 1, Pag. 487, 1912). 
