Jan. 26, *9*4 
A Bacterial Blight of Gladioli 
227 
Beef bouillon clouds only moderately but forms a thick, yellow rim and 
a thin pellicle. The rim and pellicle are extremely viscid. The growth is 
viscid in most media but especially so in beef infusion peptone media. 
Liquefaction of gelatin is not rapid at 18 to 20° C. Colonies on plates 
showed first signs of liquefaction on the fifth day. In stab cultures the 
upper fifth of the medium was liquefied by the seventh day. Blood serum 
becomes translucent and partly liquefied. 
On potato cylinders the growth is pale yellow and abundant, usually 
covering the cylinder and filling the water with a thick growth. The 
potato is slightly browned. 
A slight acidity is produced in milk cultures. A soft, smooth curd 
forms, but it is rapidly and completely digested. As the casein is digested 
the medium becomes translucent,but the translucency is obscured by the 
large quantity of almost opaque, viscid substance that practically fills 
the medium. Heavy, yellow, viscid rims and yellow sediment develop 
in milk cultures. Tyrosin crystals are formed. 
Litmus in milk is slowly reduced. 
No gas is formed from dextrose, saccharose, lactose, maltose, galactose, 
or glycerin. Slight amounts of acid are produced in cultures containing 
dextrose and saccharose. With lactose and glycerin the reaction is 
consistently alkaline. 
Growth is scanty in Cohn's and Uschinsky’s solutions; scanty and 
fugitive in Fermi's solution. 
Ammonia and hydrogen sulphid are produced in cultures. Several 
tests for indol have given negative results. Controls of B. coli gave positive 
indol reactions. 
Nitrates are not reduced. 
Sodium chlorid is not well tolerated, 1 per cent definitely reducing 
growth, and no growth occurring above a 2 per cent concentration. 
The optimum reaction for growth in peptone beef bouillon is +14 to 
+ 17 (P H 6.8 to 6.5). 4 Even under only slightly adverse conditions 
growth is slow, and no growth occurs if the media is much below or 
above the optimum. For example, in one of the experiments for the 
determination of the thermal death point, peptone beef bouillons titrat¬ 
ing + 6, +10, +15, and +17 (P H 7.6, 7.2, 6.7, and 6.5) were used. All 
four were made from the same beef infusion stock. The tubes had the 
same amount of inoculum, and the heating tests were simultaneous. 
Cultures in +15 and +17 survived higher temperatures than those in 
-f 6 and +10. In the controls growth was retarded in the +6 and +10 
and never became so heavy as in the +15 and +17 media. The mini¬ 
mum is at o (P H 8.2), the maximum at +25 (P H 5.7).. 
The toleration of organic acids was tested by adding 0.1 and 0.2 per 
cent, respectively, of citric, malic, and tartaric acids to a neutral bouillon 
base. The bacteria grew normally in the o. i per cent acids (+ 15, P H 7.0) 
and not at all in the 0.2 per cent ( + 27, P H 5.7). 
TEMPERATURE RELATIONS 
In beef bouillon the optimum temperature is near 30° C.; the minimum 
is below 2 0 . Growth begins but does not continue at 36°. The thermal 
death point is near 50°. 
< Quirk, Agnes J., and Fawcett, Edna H. hydrogen-ion concentration vs. titratable acidity 
IN culture mediums. In Jour. Infect. Diseases, v. 33, p. 20. 1923. 
