10 
North Carolina Agricultural Experiment Station 
without appreciable hydrolysis and the sterile sugar can then be added to 
sterile media, using aseptic precautions to prevent the necessity of subsequent 
sterilization. Accordingly, stock 20 per cent sugar solutions in distilled water 
were sterilized in the autoclave at 10 pounds for 10 minutes. Stock nutri¬ 
ent agar and bouillon were made as usual, were adjusted to the desired hydro¬ 
gen ion concentration l>y comparison with the buffer color standards, were 
flasked and sterilized in 95 cc. quantities and then set aside until cool. 
When 5 cc. of the sugar solution was added to such quantities of media, using 
aseptic precautions, it contained 1 per cent of the sugar to be investigated. In 
the case of agar, which had an initial hydrogen ion concentration of pH= 
7.0-7.2 the sugar was added to cooled but not yet solid media. It was then 
poured before the agar had set, into sterile test tubes, and was incubated for 
48 hours to determine its freedom from contamination. 
In making solid indicator media, sterile litmus solutions were prepared and 
the litmus was added in the same manner as the sugars. After growth had 
proceeded for a given time, in bouillon cultures containing sugars, which were 
used to check the results with solid indicator media, tests for acid were made 
by adding brom cresol purple or phenol red to the cultures and comparing 
them directly with the standards and with the uninoculated tubes. This last 
precaution seems to be of significance in the light of findings by Grace and 
Highberger (3) on variation in uninoculated media. 
Litmus agar. Litmus agar in triplicate sets for each strain and for 
each of the sugars was used as indicator media. Each series included dextrose, 
saccharose, lactose, maltose and glycerine. 
Furthermore, each series was inoculated from the same stock culture and all 
cultures were incubated at 28 degrees C. with the resultant reaction indicated 
by the litmus. No differences in strains were apparent on dextrose since the 
blue had practically disappeared from all tubes by the seventh day and they 
were reddened throughout. A slight reddening began on all strains on saccha¬ 
rose after three days, and the upper part of the stab was definitely reddened 
by the seventh day. On each of lactose, maltose, and glycerine, Nos. 268 and 
269 were able to bring about a slight change which was first apparent after 
about a week and the upper portions of the tubes became with age, a reddish 
brown, whereas, Nos. 211, 270 and 19 produced no acid from these sugars. 
Sugar broths. In order to check the changes in reaction in solid media, 
the several carbon compounds were employed in 2 per cent peptone solutions. 
The media which had been adjusted to pH=7.2 were inoculated and the changes 
after seven days were determined by comparison with buffer color standards. 
These data in terms of pH concentration are presented in the following tabu¬ 
lation : 
Reaction to Sugars in Peptone Broth by Soybean Blight Organisms 
Strain 
Dextrose 
Saccharose 
Maltose 
Lactose 
Glycerine 
268 _ 
5.4 
6.2 
6.7 
6.5 
6.2 
269 _ 
5.4 
6.4 
6.4 
6.4 
6.4 
19 _ 
6.6 
7.0 
7.4 
7.5 
7. 6 
211 _ 
6.4 
6.6 
7.6 
7.4 
7.6 
270 __ 
6.3 
6.4 
7.6 
7.6 
7.6 
