( 161 ) 
acetate and tartrate, whereas cane-sugar, milk-sugar, mannite and 
raffinose produce no growth at all. Ammonium-chloride may also 
serve as source of nitrogen, when using tartrate for carbon nutrition. 
Pepton, asparagin, and kalium-asparaginate may simultaneously 
serve as C and N nutriment. 
The bacterium secretes neither invertin nor diastase and does not 
split indican or ureum. In broth it produces no sulphureted hydrogen 
but a little indol. 
In the “tube experiment” in broth gelatin with 0,1 °/, KNO,, 
bubbles of nitrogen are exclusively seen to form at a little distance 
from the meniscus, and moreover, the culture of this species not 
succeeding in a bottle wholly filled with a culture liquid containing 
nitrate, we must needs conclude, that /. vulpmus wants considerable 
quantities of oxygen for the denitrification. 
As regards the other species, which form gas bubbles also in the 
depth of the tube, I have come to the conviction that they too, 
want traces of free oxygen to this end. 
Notwithstanding this different behaviour towards free oxygen, the 
motion figure, like that of B. stutzeri, shows the spirillum type. 
By modifying the nutrient liquids and temperatures [ have succeeded, 
as observed above, in accumulating various other denitrifying bacteria, 
beside those deseribed. Thus I obtained, at 37° C. with calcium-citrate 
and 0,2°/, KNO,, under exclusion of air, and using garden soil for 
material of infection, the spirillum-like . mdigoferus Voors), which 
denitrifies only feebly, but is interesting by its indigo-like pigment. 
When using sewage water, I obtained a strongly denitrifying, liquefying, 
blue pigment bacterium, not yet deseribed. 
Of all these experiments however, the result is not constant enough 
to be inserted here. 
6. Summary and conclusions. 
1st. The fundamental principle of my accumulation experiments 
was partly or completely to prevent the access of air. By this means 
I have succeeded, by cultivating in solutions of organic salts and 
nitrate, only by repeated transports in the same liquid, in bringing 
many denitrifying bacteria to a more or less perfectly pure culture. 
1) Crarssen. Ueber einen indigoblauen Farbstof erzeugenden Bacillus aus Wasser. 
Centrbl. f. Bakt. 1890, Bd. 7, S. 13. 
Voces. Ueber einige im Wasser vorkommende Pigmentbacteriën, Centrbl. f. Bakt, 
1898, Bd. 14, S. 301. 
