174 
Journal of Agricultural Research 
Vol. XXIX, No. 4 
Titration of these media showed that 
the 0.1 per cent acid media ranged from 
+ 20 to +26, the 0.2 per cent from +42 
to +43, and the 0.3 per cent from +63 
to +78. 
Temperature relations. —In pep¬ 
tone-beef bouillon the optimum tem¬ 
perature for growth is about 32° C. 
Clouding occurs more promptly at 34° 
to 35° than at 30° to 32°, but after 24 
hours growth is better at the lower 
temperature. 
The minimum temperature for growth 
is at 8° to 9° C. The organism re¬ 
mained alive for 4 months, and probably 
longer, at 1° to 2°. The maximum tem¬ 
perature is 40°. Various trials indicate 
a thermal death point at 52° to 53°. 
Occasional cultures have given growth 
after a 10-minute exposure to 54°. 
Freezing. —The freezing for 1 hour of 
24-hour-old beef bouillon cultures re¬ 
duced the number of bacteria 40 to 50 
per cent. 
Desiccation. —Drops of beef bouil¬ 
lon cultures 18 to 48 hours old were 
transferred to sterile cover glasses and 
dried in sterile Petri dishes. The 
results indicate that the younger cul¬ 
tures are less resistant than older. 
This may be due to the fact that the 
older cultures are already somewhat 
viscid, do not spread so well, and prob¬ 
ably retain moisture longer than the 
young cultures. Young cultures re¬ 
sisted drying from 4 to 5 days. Older 
cultures gave growth up to 14 days. 
Effect of sunlight. —Beef-peptone 
agar plates, thinly sown, were exposed 
on ice to sunlight in July at 11 a. m. 
Ten minutes’ exposure killed 50 to 70 
per cent and 20 minutes’ exposure 
killed practically all the bacteria. 
Vitality. —At Washington room 
temperatures the bacteria in culture 
media die in 7 to 9 months. This may 
be due partly to drying of the media. 
At lower temperatures (14-18° C.) cul¬ 
tures live more than a year but the 
athogenicity is reduced by age. 
ome young cultures were mixed with 
sterile soil which was then placed at 
1-2° for 4 months, then at 8-9° for 3 
weeks. From a bit of this soil the bac¬ 
teria were isolated in great numbers. 
These tubes then remained in a closet 
at room temperature and the bacteria 
were alive and virulent 11 months after 
being put in the tubes. After 15 
months isolations showed the bacteria 
still very much alive but no pathogenic 
test was made. No growth was secured 
from lesions on leaves kept at room 
temperature for 7 months. 
Variations. —Cultural studies and 
infection experiments have proved that 
the various isolations are similar in their 
essential characteristics, though not 
absolutely alike. One isolation from 
plants grown in Virginia liquefies gela¬ 
tin more rapidly than the one selected 
as the type. Another from Michigan 
produces more abundant growth on 
artificial media. Some isolations are 
less viscid than others and occasional 
sets of beef bouillon cultures never 
become viscid. The bacteria isolated in 
1913 browned beef media. Later isola¬ 
tions have not discolored beef media 
but some of them have slightly browned 
potato agar plus dextrose. The brown 
growth on potato agar plus dextrose 
occurs in most but not all of the isola¬ 
tions. 
Group numbers. —The group num¬ 
ber, according to the descriptive chart 
(1907) of the Society of American Bac¬ 
teriologists, is 211.2222022. According 
to the 1920 chart it is 5322-31130-1222. 
TECHNICAL DESCRIPTION 
Bacterium marginatum, n. sp. 
Cylindrical rods rounded at ends, 
occurring singly and in pairs; 0.8 to 
1.8 by 0.5 to 0.6 m; aerobic; motile by 
means of one to four bipolar flagella; 
no spores; capsules present; stains read¬ 
ily but often shows granular structure; 
Gram-negative; not acid fast. 
On beef agar the colonies are white, 
circular, becoming more or less irregu¬ 
larly lobed; center smooth, almost 
hemispherical, surrounded by a wide 
border which is thin at first becoming 
thick and contoured. 
Liquefies gelatin and softens blood 
serum; produces slight amount of acid 
in milk, then becomes alkaline; digests 
casein; produces acid in cultures with 
various sugars, especially in galactose 
and dextrose. Nitrates are not re¬ 
duced. No gas is produced. Slight 
amounts of indol, hydrogen sul¬ 
phide, and ammonia are produced. 
Grows well in Uschinsky’s, Fermi’s, 
and in Cohn’s solutions. Viscid in 
most media. Not viscid in Fermi. 
Temperature for growth, maximum 
40° C., minimum 8° to 9°, optimum 30 
to 32°. Thermal death point about 
53°. Remains alive at temperatures 
below 9° for 4 months or more; not 
particularly sensitive to drying; freez¬ 
ing for 1 hour killed 40 to 50 per cent; 
sunlight for 10 minutes killed 50 to 70 
per cent. 
Pathogenic on gladiolus leaves and 
corms, producing reddish brown lesions, 
circular to elongated on the leaves, and 
circular, shallow brown pits on the 
corms. 
Specimens of the disease on leaves 
and corms have been deposited in the 
