Feb. 1,1925 
Decomposition of Proteins and Amino Acids 
279 
developing with the amount of energy 
made available. The small nonspore¬ 
forming bacteria, utilizing protein deri¬ 
vatives and breaking these down to 
ammonia, will obtain a comparatively 
larger amount of energy; this fact, as 
well as the smaller size of the cell, may 
be the cause for the development of a 
large number of individuals. 
It remains to be seen whether this 
holds true also for other bacteria, or 
the two bacteria used in this study 
just happen to be exceptions. 
One more point remains to be dis¬ 
cussed in this preliminary study on the 
decomposition of proteins and their 
derivatives by microorganisms;' name¬ 
ly, the influence of carbohydrates upon 
the decomposition of the proteins and 
upon ammonia accumulation. It was 
pointed out above that the theory 
that 11 available carbohydrates exert 
a protective action upon the decom¬ 
position of proteins by microorganisms” 
should be modified, since, as seen in 
the case of the Actinomyces, some 
organisms are capable of utilizing 
proteins as sources of energy, even in 
the presence of dextrose, probably the 
most available of all carbohydrates for 
microorganisms, including actinomy- 
cetes. Table IX contains a few data 
on the influence of other carbohydrates 
upon the decomposition of casein by 
bacteria and fungi. Since B. cereus 
isQunable to decompose celluloses, a 
strong cellulose-decomposing bacterium 
Bad. fimi of Kellerman and associates, 
was used. In the case of B. cereus , 
both cane sugar and starch exerted 
a protective action upon ammonia 
accumulation, starch to a lesser extent, 
possibly because it is not so readily 
available as the sugars. In the case of 
Trichoderma, cane sugar and starch 
also exerted a protective action, while 
cellulose did not. Trichoderma, one of 
the strongest cellulose-decomposing 
organisms ever tested in this labora¬ 
tory, behaves towards the protein as 
if the cellulose were not present in the 
medium at all; in other words, it pre¬ 
fers the protein as a source of energy to 
the available carbohydrate (cellulose). 
The Bad. fimi , however, decomposed 
the protein only to a very limited extent 
and preferred the carbohydrate as a 
source of energy. 
The above theory should therefore 
be modified to a simple problem of 
metabolism, which holds true not only 
for microorganisms but for all living 
beings that depend for their energy 
upon complex substances; namely, 
that a living being derives its energy 
from a substance, which is most avail¬ 
able to it and which may be specific 
for a particular organism; a large 
number of microorganisms prefer cer¬ 
tain simple available carbohydrates 
to proteins as sources of energy, and 
in the presence of those, the proteins 
will be utilized only as sources of nitro¬ 
gen; therefore, ammonia, which is 
chiefly a product of utilization of pro¬ 
teins as sources of energy, will not 
accumulate. 
SUMMARY 
A study has been made of the nature 
of decomposition by two fungi, two 
bacteria, and one Actinomyces of cer¬ 
tain pure, amino acids and casein; the 
latter was used in a synthetic medium 
as sources of nitrogen alone and of 
Table IX.— Influence of various carbohydrates (2 per cent) upon the decomposition 
of casein by microorganisms ° 
Organism 
Carbohydrate 
B. cereus 
Trichoderma 
Bact. fimi 
NHj-N 
in 100 
c. c. 
NHs-N 
in 100 
C. C. 
pH 
NHj-N 
in 100 
c. c. 
NHa-N 
in 100 
c. c. 
Weight 
of dry 
myce¬ 
lium 
pH 
NH 2 -N 
in 100 
c. c. 
NHa-N 
in 100 
c. c. 
pH 
Control.. 
None _ 
Mg. 
8.4 
40. 28 
27.54 
28.33 
Mg. 
1. 76 
32.96 
3.00 
8.86 
7.7 
8.2 
4.7 
5.1 
Mg. 
8.4 
40.70 
47.17 
20.17 
* 30.32 
Mg. 
1.76 
19.77 
10.74 
9.82 
34.06 
Mg. 
94 
173 
643 
96 
7.7 
8.1 
8.0 
7.1 
8.2 
Mg. 
\ 8 - 4 
Mg. 
1.76 
7.7 
Cane sugar. 
Starch_ 
Cellulose. 
« 12.88 
1.12 
6.2 
• Incubation 8 days; for cellulose flasks, 16 days. 
* No cellulose decomposed. 
c 65 mg. of cellulose decomposed. 
