Studies on Physiology of Some Plant Pathogenic Bacteria 
29 
Experiment II—The Nature of the Change in Reaction in 
Beef-extract Broth 
In these tests, a 0.3 Liebig’s beef extract broth with an initial reaction of 
pH 7.2 was employed. The daily changes in reaction with each of the organ¬ 
isms is shown in the following table: 
Table 3.— Final pH in 0.3 Beef Extract Broth 
Organism 
Age of Cultures in Days and pH Concentration 
Days 
1 
2 
3 
4 
5 
6 
pH 
pH 
pH 
pH 
pH 
pH 
Bacterium tabacum 
7.2 
7.4 
7.4 
7.4 
7.6 
7.8 
Bacterium angulatum. 
7.2 
7.4 
7.4 
7.6 
7.6 
7.8 
Bacillus carotovorus 
7.2 
7.2 
7.2 
7.4 
7.6 
7.8 
Bacterium glycineum_ 
7.2 
7.2 
7.2 
7.4 
7.6 
7.6 
Bacterium sojae. 
7.2 
7.2 
7.2 
7.4 
7.6 
7.6 
Bacterium campestre. . 
7.2 
7.2 
7.2 
7.4 
7.4 
7.4 
This medium supports meagre growth in the case of all of these organisms so 
that little significance perhaps can be attached to this experiment. All cul¬ 
tures, however, appear to become progressively more alkaline. 
Experiment III—The Changes in Reaction in Peptone Broth 
One per cent Armour’s peptone broth with an initial pH of 7.2 was used. 
In Table 4 are shown the pH concentrations at given intervals. 
Table 4.-— -Changes in pH Concentration in 1 Per Cent Armour’s 
Peptone Broth 
Organism 
Age of Cultures in Day 
3 and pH Concentration 
Days 
1 
2 
4 
6 
8 
11 
pH 
pH 
pH 
pH 
pH 
pH 
Bacterium tabacum - _ 
7.2 
7.4 
7.6 
8.2 
8.4 
8.4 
Bacterium angulatum_ 
7.2 
7.4 
7.6 
8.2 
8.4 
8.4 
Bacillus carotovorus.- 
7.0 
7.0 
7.0 
7.4 
7.4 
7.6 
Bacterium glycineum_ 
7.2 
7.2 
7.6 
8.0 
8.4 
8.4 
Bacterium sojae_ .. . 
7.2 
7.2 ' 
7.4 
7.8 
8.2 
8.4 
Bacterium campestre _ 
7.2 
7.4 
7.8 
8.0 
8.0 
8.4 
The only point of interest in this table is the slight but definite increase in 
acidity in cultures of B. carotovorus. This increase is followed by a reversal 
of reaction with a subsequent gradual increase in alkalinity. These changes 
are more marked in plain bouillon as shown in Table 5 which follows. 
A similar increase in hydrogen ion concentration in sugar free broth has 
been noted in the case of a number of organisms, including Micrococcus aureus 
