GROWTH AND PIGMENT PRODUCTION OF PSEUDO- 
MONAS JANTHINA. 
BY HARRY F. WATT. 
The study here presented was undertaken to determine 
the growth characters of Pseudomonas janthma and the re- 
lations between color production and composition of 
medium. 
The culture used was derived from the water of a farm 
well in northwestern Iowa. From its morphology and 
growth characters it was determined to be Pseudomonas 
janihina (Zopf.) Chester. 
Morphology.— -Bacillus, 0.5 to 0.8 x 1.5 to 5 microns, 
ends rounded, motile by means of one or two polar 
flagell 80 . Stains well using Gram’s method. No spore 
production, stains readily with ordinary analine dyes. 
Cultural Characters, Gelatin Plates. — Colonies appear 
first as small yellowish, or whitish dots, liquefying the 
the gelatin, and eventually with greenish purple centers 
and violet borders. Microscopically fragmental, grumose. 
Gelatin Stah. — Gelatin liquefied after some time, growth 
at first whitish, becoming violet. 
Agar Slant. — Growth smooth, spreading, thin at first and 
whitish yellow, soon becoming deep violet or even violet 
black and very much crumpled, tough. 
Potato. — Growth on the potato at first whitish or whitish 
yellow, soon developing small purple points. 
Bouillon. — At first turbid, but soon developing a mem- 
brane at first whitish, soon turning violet. 
Milk. — Milk not coagulated, upper portion violet. 
Physiological Characters. — In the cultivation on the 
above media great variations in color production were 
(173) 
