Feb. 1, 1925 
Decomposition of Proteins and Amino Acids 
277 
When Bad. fluorescens and B. ceresu 
were inoculated into the same solution, 
the latter decomposed the casein, while 
the former decomposed a large part of 
the simple amino compounds, as soon 
as formed, with the formation of am¬ 
monia. The number of cells of Bad. 
fluorescens greatly exceeded those of B. 
cereus; the culture looked and smelled 
like a typical Bad. fluorescens culture. 
The accumulation of amino nitrogen in 
the mixed culture never reached as high 
a point as in the culture of B. cereus 
alone; so that, in 6 days, the mixed 
culture produced a little more than half 
as much amino nitrogen, as B. cereus 
alone did, and over twice as much 
ammonia. 
The question often arises in the 
study of soil microbiology: Just what 
part is played in the soil by a large 
number of bacteria and other organisms 
incapable of decomposing native pro¬ 
teins, celluloses, and other complex 
compounds added to the soil? It may 
be that here will be found the answer to 
this question; namely, that they attack 
the products resulting from the decom¬ 
position of complex compounds by those 
organisms that are able to do so. 
Various instances of such associative 
action are on record as between the 
nitrate-forming and nitrite-forming 
bacteria, nitrogen-fixing and cellulose- 
decomposing bacteria, etc. There is no 
reason to doubt that a similar associa¬ 
tive action is found here between the 
large spore-forming and other strongly 
proteolytic bacteria, (aerobic and an¬ 
aerobic) and fungi, on the one hand, 
and the small, nonspore forming and 
nonproteolytic bacteria on the other. 
This will also explain the apparent dis¬ 
crepancy between the numbers of the 
spore-forming and nonspore-forming 
bacteria in the soil, the former being 
present there only as 5 to 10 per cent of 
the flora developing on the plate, and 
the latter as 50 to 80 per cent. This 
discrepancy led Conn (4) to doubt the 
activity of the spore formers in the soil. 
The explanation here may again be 
very simple: The strong proteolytic 
cells will obtain a comparatively small 
amount of energy from the hydrolysis 
of the proteins to amino acids, even 
when they transform a part of these to 
ammonia; this and the large size of the 
cell may account for the fact that only 
a limited number of cells are capable of 
Table VIII .—Decomposition of casein by B. cereus, by Bad. fluorescens and by 
both organisms in association 
Organism used 
Age of culture 
B. cereus 
Bact. fluorescens 
Total N 
in 100 c. c. 
solution 
NH2-N 
in 100 c. c. 
nh 3 -n 
in 100 c. c. 
Weight 
of 
pellicle 
pH 
Total N 
in 100 c. c. 
solution 
NH 2 -N 
in 100 c. c. 
nh 3 -n 
in 100 c. c. 
! 
pH 
Mg. 
Mg. 
Mg. 
Mg. 
Mg. 
Mg. 
Mg. 
Control.. __ . 
140.6 
7. 57 
2.30 
7.1 
140.6 
7.57 
7.1 
1 day_ 
9. 55 
3.30 
7.1 
6.34 
S.00 
7.1 
2 days_ _ 
15.30 
3.00 
7.1 
9.86 
1.04 
7.1 
4 days.. . . 
135.03 
29.93 
12.94 
50 
7.4 
7.90 
1.40 
7.1 
6 days_ 
128.1 
44.89 
16.62 
73 
8.0 
8. 21 
2.06 
7.3 
9 da vs 
113. 2 
38.93 
40.86 
113.2 
8.5 
7.46 
3.00 
7.3 
15 days. 
82.56 
24. 62 
46. 52 
209 
8.9 
139.6 
9.86 
0.88 
7.3 
Organism used—B. cereus+Bact. fluorescens 
Age Of culture 
Total N 
in 100 c. c. 
solution 
NH 2 -N 
in 100 c. c. 
nh 3 -n 
in 100 c. c. 
Weight 
of 
pellicle 9 
pH 
Control__ 
Mg. 
140.6 
Mg. 
7. 57 
Mg. 
2.30 
Mg. 
7.1 
1 day_______ 
7. 26 
1.76 
7.1 
2 days......... 
18.42 
7.96 
7.2 
4 days__ ____ 
119.80 
23.31 
27.86 
156 
8.2 
6 days______ 
115.50 
27.68 
35.36 
185 
8.9 
9 days____- 
92.14 
13.90 
56.76 
203 
9.4 
15 days_____ 
91.22 
10.84 
59. 72 
224 
9.4 
Approximate. 
