NITRATES AND NITRITES 163 



Bact. filefaciens, Jensen. A non-motile organism isolated 

 from an old impure culture of Bact. Stutzeri. Rods usually 

 .5 to 1.5 p long and .5 to .75 thick; older cells stain irregularly. 



Gelatine. Not liquefied. Surface colonies thin, dull and some- 

 what slimy; deep colonies very small, white, round. Stab beaded, 

 with well developed white surface growth. 



Agar. Surface colonies dirty white, slimy, can be drawn out 

 into long strings. 



Nitrate Bouillon. Denitrification in one to two days at 30 C. ; 

 liquid pretty clear with a stringy sediment. 



Bact. nitrovorum, Jensen. A non-motile organism isolated 

 from horse dung. Rods very small, .5 to i p long, .5 p thick. 



Gelatine. Not liquefied. Surface colonies very small, .2 to 

 5 mm. in diameter, white, slimy, and round; deep colonies scarcely 

 visible. Stab slender and beaded, its surface growth 6 to 10 mm. 

 diameter, with concentric rings sometimes. 



Agar. Surface colonies, dirty, white, slimy, 2 to 4 mm. in 

 diameter. 



Nitrate Bouillon. Slightly turbid in twenty-four hours ; deni- 

 trification in two or three days, with little froth ; sand-like 

 sediment. 



Vibrio denitrificans, Sew. A peculiar variable bacterium 

 isolated by Sewerin from horse dung. In bouillon comma and 

 spirillum forms occur as well as rods i to 10 /* long; branched 

 and triangular involution forms are also found after four or five 

 days. On solid media usually rods 2 to 4 /x long, .5 p, thick. 



Gelatine. Not liquefied. Small, round, white surface colonies, 

 slow in development. Stab beaded. 



Agar. In two days at 30 C. small (i to 2 mm.), bluish- white, 

 slimy colonies. 



Nitrate Bouillon. Denitrification occurs in two or three days 

 with turbidity and only a slight frothing. 



Vibrio denitrificans, Hoflich. A motile vibrio isolated from 

 horse and cow dung, straw and soil. Both rods and vibrio forms 



