266 
Joumal of Agricultural Research v 0 i. xxx, no. 3 
total nitrogen by the Kjeldahl method. 
The ammonia nitrogen was determined 
in an aliquot portion (25 c. c.) by the 
Folin (7) aeration method, using 5 c. c. 
■of 40 per cent Na 2 C (>3 solution and 
some heavy oil, to prevent foaming, 
N 
and aerating, for 4 hours, into JQH 2 SO 4 , 
then titrating. The amino nitrogen of 
the liquid was determined by the Van 
Slyke micro method (31, 32 ), after the 
ammonia had been aerated, or, in the 
original solution, allowing for the 
ammonia content by subtracting one- 
half of the ammonia nitrogen from the 
total amino nitrogen (shaking 5 min¬ 
utes) . The total nitrogen in the solu¬ 
tion was obtained by determining it in 
an aliquot portion of the filtered 
culture. The residual dextrose was 
determined by the Bertrand method. 
The hydrogen ion concentration of the 
medium was determined by the colori¬ 
metric method. In view of the fact 
that, in the case of the bacteria, the 
mere filtration through paper gave the 
weight of the bacterial pellicle but not 
of the cells throughout the medium, 
attempts have been made to obtain the 
amount of the latter by carefully 
acidifying with acetic acid, then filter¬ 
ing the coagulated mass. This process 
has been carried out successfully only 
in the case of the bacteria growing on 
glutamic acid media. Th 6 total weight 
of the bacterial cells, in the other 
culture, is therefore only approximate 
and indicates merely the weight of the 
pellicle. In the case of the fungi and 
the Actinomyces, however, filtration 
through paper is sufficient to separate 
the growth from the culture fluid 
completely. 
In all cases duplicate cultures were 
prepared, using an uninoculated con¬ 
trol for every fresh lot of medium; only 
the averages of the two determinations 
are recorded; in those cases where the 
results in the duplicates varied mark¬ 
edly they were reported separately. 
Several of the experiments were re¬ 
peated, but unless markedly different 
results were obtained (as in the case of 
the 1.4 per cent glutamic acid) they 
were not recorded. 
Before discussing the various chemi¬ 
cal changes produced by the different 
microorganisms it may not be out of 
place to point out several outstanding 
characteristics in the growth of these 
organisms. The Bact. fluorescens used 
the carbon and especially the nitrogen 
of the various amino acids in a most 
excellent way, producing a heavy pellicle 
on the surface, especially so in the 
presence of dextrose; the characteristic 
fluorescent pigment was produced in 
most cases on the second or third day 
of growth only in the amino-acid media 
not containing any dextrose. The 
B. cereus , however, made no growth 
at all with glycocoll, alanine, and 
phenylalanine and only very little 
growth with glutamic acid and as¬ 
paragine, •which indicates that this 
organism is not only incapable of 
utilizing the carbon in at least the 
amino acids tested, but can not even 
make use of their nitrogen. Such a 
distinctive difference between these two 
very common groups of soil bacteria, 
one (the Bad. fluorescens) a nonspore¬ 
forming organism and the other ( B . 
cereus) a spore former, was very un¬ 
expected. When these two organisms 
were • inoculated into the synthetic 
medium containing purified casein, the 
exactly reverse phenomenon took place 
—the B. cereus developed very rapidly, 
accompanied by a vigorous decomposi¬ 
tion of the casein, while the Bact. 
fluorescens made only a mere trace of 
growth without bringing about any 
noticeable hydrolysis of the casein. 
Thus one organism proves to be strong¬ 
ly proteolytic, capable of rapidly hydro¬ 
lyzing proteins (this was found to hold 
true also for purified vegetable proteins, 
as will be shown later), but unable to 
attack some simple amino acids; the 
other is unable to attack native 
proteins, but is capable of making a 
very abundant growth on the protein 
cleavage products—the amino acids. 
In view of the fact that these two 
organisms do not occur in nature in 
pure culture but in constant associa¬ 
tion, and the further fact that one can 
readily utilize the products of the other, 
the idea suggested itself that proteins 
could more rapidly be reduced to the 
ammonia stage by the combined action 
of these two organisms, one utilizing 
the products of the other. This has 
actually been found to be the case, as 
will be pointed out later. 
Another interesting phenomenon was 
observed in the case of the fungi. 
Whenever pure amino acids have been 
used as the only source of carbon and 
nitrogen, the fungi made a rather lim¬ 
ited growth, as shown in Tables I to IV; 
in most cases not over 50 mg. per 100 
c. c. of medium. One could, therefore, 
be led to a hasty conclusion that. fungi 
can not readily utilize amino acids as 
a source of carbon. On close examina¬ 
tion of the data, however, a more ap¬ 
propriate explanation of this phenome¬ 
non is found. In all cases whenever 
amino acids have been used as sources 
of carbon and nitrogen, the reaction is 
changed to alkaline, owing to the rapid 
accumulation of ammonia. In view of 
