*38 
Journal of Agricultural Research 
Vol. XXI, No. * 
To determine the tolerance of true acidity as indicated by the hydrogen- 
ion concentration, duplicate series of tubes of beef-pep tone bouillon 
were adjusted with normal hydrochloric acid to the P H values presented 
below by the comparison of the indicator methyl red in the tubes with 
a set of standards. For the P H 6.4 series, brom cresol purple was used. 
After inoculation these tubes were incubated at 22 0 C. The results are 
presented in Table II. 
Table II .—Tolerance of acidity as indicated by growth in media at various hydrogen-ion 
concentrations, incubated at 22 0 C. 
Incubation 
period. 
Ph 6.4. 
Ph 5.8. 
Ph 5.6. 
Pn 5.4. 
Ph 5.3. 
% days.... 
Heavy growth 
Light growth. 
No growth.... 
No growth.... 
No growth. 
5 days.... 
Light growth. 
Light growth. 
Do. 
The tubes of P H 5.3 were then heavily reinoculated from a slant cul¬ 
ture, and in 3 more days growth was evident. The acid range was 
then extended and the test repeated. This set of cultures was incu¬ 
bated at 25 0 C. The results are presented in Table III. 
Table III .—Tolerance of acidity as indicated by growth in media at various hydrogen-ion 
concentrations, incubated at 25 0 C. 
Incu¬ 
bation 
period. 
Ph 5 4- 
Ph 5 - 3 . 
Ph 5.2. 
Ph 5. 
Ph 4.8. 
Ph 4-7. 
Ph 4.6. 
3 days.. 
4 days., 
xa days. 
No growth. .. 
Light growth. 
Heavy growth 
No growth. .. 
Light growth. 
Heavy growth 
No growth. 
.do. 
.do. 
No growth. 
.do. 
.do. 
No growth. 
.do. 
.do. 
No growth. 
.do. 
.do. 
No growth. 
Do. 
Do. 
At the end of 12 days the tubes in which no growth had occurred were 
reinoculated from one of the cultures that grew at P H 5.3. In 7 days 
growth had occurred in both the P H 5.2 tubes and in one of the two 
P H 5 tubes, but in none of the others. Therefore, the upper limit of 
tolerance of the hydrogen-ion concentration may be taken as P H 5.3, 
although this was increased to P H 5.2 and P H 5 by reinoculation from 
cultures growing in media of P H 5.3. Development is noticeably checked 
by a P H value of 5.6, and P H 6.4 is more favorable than P H 5.8. 
TEMPERATURE RELATIONS 
The organism grows well in a wide range of temperature. Slant and 
plate cultures on potato agar, inoculated by strokes made from a water 
suspension of the bacteria and incubated in moist chambers at io°, 15 0 , 
18 0 , 22 0 , 25 0 , 30°, and 35 0 C., proved that the organism was able to 
develop at all these temperatures. At io° the growth was very slow, at 
15 0 it was more abundant, and at 18 0 fairly good growth occurred. The 
