Dec. 17,1917 
Bacterial-Blight of Barley 
635 
Optimum reaction and toleration limits. —Peptonized beef bouillon was used 
with sodium hydrate as the alkali under test and hydrochloric as the acid. Bouillons 
were prepared titrating +25, +20, +10, +5, o, —20, and —30, and uniformly inocu¬ 
lated from a 4-day-old bouillon culture. At the end of 48 hours, growth was evident 
in -f 10, +5, and o. Clouding was weak in the o bouillon at this time, but the +5 and 
+ 10 were heavily clouded. At the end of four days a pellicle was evident on the 
+10 tubes. The -f 5 later formed a weak pellicle, but none formed on the o. Gradual 
clearing began on the fifth day, but the cultures never cleared entirely. The sediment 
in the +10 was somewhat flocculent, but in the +5 and o it had more of a slimy, stringy 
consistency. None of the other reactions showed any growth. 
It seems evident, therefore, that +10 Fuller’s scale represents the optimum reaction 
and that the organism is highly sensitive to both alkali and acid. 
Another test was made of acid toleration, using +10 bouillon as the basic medium, 
to which was added 0.1 and 0.2 per cent, respectively, of malic, tartaric, and citric 
acids. The cultures were kept under observation for 20 days following inoculation, 
but no growth was observed in any of the acidulated tubes. 
Uschinsky’s solution. —A moderate, uniform clouding was noticeable on the 
fifth to eighth day. The clouding never became heavy and no pellicle was formed. 
There was slight change in the medium. Only a slight yellow tinge was given to it 
and a small amount of yellow sediment. The bacteria formed long chains in this 
medium. 
Fermi’s solution. —No growth. 
Cohn’s solution.—N o growth. 
Starch agar. —No evidence of diastasic action on potato starch suspended in 
peptone-beef agar, tests being made with potassium iodid-iodin. 
Reduction op nitrates. —Cultures in nitrate bouillon were tested with Tromms- 
dorf’s reagent, first after 24 hours and repeatedly thereafter, and gave negative tests for 
nitrites. At the end of 30 days the cultures gave strong tests for ammonia and nitrates 
but negative test for nitrites. It is doubtful if nitrates are reduced, since good tests for 
ammonia are obtained from bouillon which does not contain potassium nitrate. 
Indol. —Tests in peptonized Uschinsky’s solution and in peptone water at the 
end of two weeks and four weeks showed slight indol production. B. coli run in 
comparison showed much stronger indol production. 
Methylene-blue in milk. —Reduction is slow, first evident at end of three weeks. 
At end of two months the cultures are white except for a surface layer and some sedi¬ 
ment which is blue. 
Blood serum. —Stroke cultures on Loeffler’s blood serum gave a moderate, wax- 
yellow, glistening, smooth, convex, filiform growth. Medium not liquefied. 
Aerobism. —The organism appears to be strictly aerobic. It does not grow in the 
closed end of fermentation tubes with any of the carbcm foods tested. No growth 
occurs in the lower end of stab cultures of agar or gelatin. Shake cultures of agar 
showed growth at or near the surface only. 
Litmus agar with sugars. —On litmus-lactose agar stroke cultures there is abun¬ 
dant growth and the medium becomes somewhat bluer, probably due to production 
of acids and ammonia, the ammonia a little in excess. The same may be said about 
the growth on litmus-maltose agar. 
On litmus-dextrose agar stroke cultures there is very abundant growth, slight 
bluing along the stroke, reduction to an amber color in two weeks. 
Optimum reaction for growth is +10 Fuller’s scale. 
TEMPERATURE RELATIONS 
In +10 peptone beef bouillon the optimum temperature was 26° C. 
or slightly above. No growth was secured at 36°, and only part of the 
tubes clouded at 35 0 . Slow growth occurred at io°; none at 6°. Nu- 
