Feb. 1, 1925 
Decomposition of Proteins and Amino Acids 
275 
have produced all or most of its 
ammonia from the amino acid group 
and not from the amide group, while 
the Bad. fluorescens seemed to have 
produced most of its ammonia from 
the amide and not from the amino 
acid group. This again goes to em¬ 
phasize that the decomposition of pro¬ 
teins and amino acids and accumulation 
of ammonia are results of the metab¬ 
olism of the particular microorganisms, 
under specific conditions. The changes 
produced as a result of decomposition 
of the protein and amino acid mole¬ 
cules do not depend so much upon the 
age of the culture as upon its develop¬ 
ment; that is, a more abundant growth 
in a shorter period of time will produce 
a series of changes parallel to its 
growth rather than its age. 
The B. cereus made only a very lim¬ 
ited growth with asparagine; in the 
rapidity of deamidization it behaved 
similarly to the Bad. fluorescens. 
CHEMISTRY OF DECOMPOSITION OF 
CASEIN 
Casein is soluble in dilute alkali solu¬ 
tions and can therefore be readily used 
as a source of nitrogen and carbon for 
the activities of microorganisms. Only 
a small amount of the casein nitrogen 
is present in the lysin group, which 
accounts for the small amount of 
amino nitrogen present in the control 
solution. The two fungi and Actino¬ 
myces readily attacked the casein; 
the two bacteria behaved, however, 
in an exactly reverse manner than 
they did in respect to the amino acids. 
The B . cereus was very active and 
Bad. fluorescens hardly attacked the 
casein at all. 
The Zygorhynchus is capable of de¬ 
composing casein, but very little 
amino nitrogen accumulates in the me¬ 
dium, showing that it decomposes the 
amino acids as soon as they are formed. 
One would almost expect this to occur, 
since this organism was capable of 
utilizing, as a source of carbon and 
nitrogen, all the amino acids previously 
tested, if only present in the proper 
concentration and with the proper re¬ 
action. The casein as such was all 
decomposed, since no precipitate was 
obtained any longer with acetic acid. 
It was not, however, completely de¬ 
composed, even in the presence of dex¬ 
trose, to carbon dioxide, water, and 
ammonia, as seen from the fact that, 
although 120.5 mg. of the nitrogen was 
present in solution, only 17 mg. of it 
was found in the form of amino and 
ammonia nitrogen. In other words, a 
large part of the nitrogen was left in the 
form of polypeptides and other protein 
derivatives, which the organism could 
not very readily and rapidly utilize as 
a source of carbon. In the presence of 
available dextrose, a large part of the 
Table VII.— The chemistry of decomposition of 1 per cent casein by micro¬ 
organisms , in the presence and absence of dextrose 
Organism used 
Dex¬ 
trose 
Age 
of 
cul¬ 
ture 
Total N in 
1 100 c. c. 
NHj-Nin 
100 c. c. 
* 
NHi— N 
in 100 
c. c. 
Dextrose in 
100 c. c. 
Dry growth 
pH 
Found 
De¬ 
crease 
from 
con¬ 
trol 
Found 
In¬ 
crease 
over 
con¬ 
trol 
Found 
Util¬ 
ized 
Weight 
Nitro¬ 
gen 
con¬ 
tent 
Per cent 
Days 
Mg. 
Mg. 
Mg. 
Mg. 
Mg. 
Mg. 
Mg. 
Mg. 
Mg. 
Control. 
None. 
126.4 
6.84 
2.10 
7.0 
Do..... 
2 
126.4 
6.84 
2.10 
1,890 
6.4 
Zygorhynchus.. 
None. 
16 
120.5 
5.9 
10.32 
3.48 
13. £2 
93 
6 .35 
7.8 
Do.... 
2 
16 
76.1 
50.3 
9.48 
2.64 
19.82 
0 
1,890 
643 
40.95 
7.8 
Trichoderma... 
None. 
6 
113.1 
13.3 
26.24 
19.40 
14.14 
154 
14.99 
7.5 
Do... 
2 
6 
70.7? 
55. 7? 
15.76 
8.92 
3.00 
560 
1,330 
452 
19.90 
4.6 
Do a . 
None. 
5 
26.17 
3.31 
59 
7.2 
Do “. 
None. 
11 
40.02 
24.29 
200 
19.62 
8.2 
Do °. 
2 
5 
16.94 
1.66 
*>1, 385 
335 
92 
5.5 
Do 0 . 
2 
11 
21.90 
9.11 
**40 
1,680 
692 
44.90 
6.6 
Actinomyces_ 
None. 
19 
108.9 
17.5 
8.94 
2.10 
31.80 
117 
9.95 
8.0 
Do. 
2 
19 
104.2 
22.2 
15.40 
8.36 
3.00 
1,380 
510 
5.1 
B. cereus_ 
None. 
10 
101.1 
25.3 
18.10 
11 . 26 
45.50 
102 
8.07 
8.4 
Do. 
2 
10 
120.0 
6.4 
9.75 
2.91 
3.30 
1,700 
190 
4.8 
Do «. 
None. 
6 
54.04 
24.92 
66 
8.5 
DO <* 
None. 
13 
24.77 
38.52 < 
156 
8.6 
Do «. 
2 
6 
25.91 
2.8 
*>1,490 
230 
4.7 
Bact. fluores¬ 
None. 
13 
124.3 
2.1 
8.34 
1.50 
2.36 
7.1 
cens. 
Do. 
2 
13 
105.8 
20.6 
7.78 
0.94 
1.12 
1,580 
310 
4.6 
° Data from a different experiment. 
*> Control in this case 1,720 mgm. 
