The bacillus is essentially a saprogenic bacterium with zymogenic
properties. A preliminary study of the chemical changes which take
place in sour hams shows that these changes are of a putrefactive
nature. Hams which had undergone spontaneous souring were compared
with hams which had been artificially soured by inoculation, and the
chemical changes were found to be identical. A chemical study was also
made of the changes taking place in egg-pork cultures of the bacillus
at different stages of growth, and these changes were found to be of a
putrefactive nature and similar in character to the changes which occur
in sour hams. Among the putrefactive products formed by the growth of
the bacillus in the egg-pork medium were indol, skatol, volatile fatty
acids, skatol-carbonic acid, and hydrogen sulphid.[4]
[4] The tests for the putrefactive products formed by the growth
of the bacillus in the egg-pork medium were made by P. Castleman,
of the Biochemic Division, who also determined the percentage
composition of the gas formed by the growth of the bacillus in the
glucose-pork-bouillon medium.
[Illustration:
BUL. 132, BUREAU OF ANIMAL INDUSTRY, U. S. DEPT. OF AGRICULTURE.
PLATE IV.
GLUCOSE BOUILLON CULTURE IN SMITH FERMENTATION TUBE AT FOUR
DAYS. CULTURE GROWN AT ROOM TEMPERATURE (20° TO 25° C.). GROWTH
CONFINED ENTIRELY TO CLOSED ARM, WITH GAS COLLECTING AT TOP.]
A more extended study is now being carried on in the Biochemic Division
of the chemical changes which take place in hams during the process of
souring, together with a further study of the chemical changes which
result from the growth of the bacillus in the egg-pork medium. The
results of this investigation will be given in a later paper.
The bacillus described in this paper belongs to the class of
putrefactive anaerobes, which are widely distributed in nature in dust,
soil, and excrementitious matters. This group of bacteria contains
both pathogenic and nonpathogenic forms. The former have received
considerable attention, but the latter have never been thoroughly
cleared up. The bacillus isolated from sour hams belongs in the latter
category, being possessed of no pathogenic or disease-producing
properties. It occurs in the dust and dirt of the packing house and
finds its way into the hams in the various manipulations to which the
hams are subjected.
The bacillus described in this paper does not seem to correspond
with any forms heretofore described. It differs from Klei bacillus
(_Bacillus fœdans_) in the following important particulars: (1) It
forms large terminal spores, whereas Klein’s bacillus formed no spores;
(2) it will grow at a temperature of 34° F., while Klei bacillus did
not grow below 50° F.; (3) it produces an acid reaction in culture
media, while Klei bacillus gave a distinctly alkaline reaction;
(4) it will grow on the ordinary nutrient media—gelatin, agar, and
broth—without the addition of glucose, while Klein’s bacillus did not;
(5) it peptonizes the casein in milk, whereas Klein’s bacillus had no
action on milk; (6) it liquefies gelatin more rapidly, causing complete
liquefaction after three weeks at 8° to 10° C., whereas Klein’s bacillus
caused only partial liquefaction after eight weeks at 20° C.; (7) it
can be conveyed
from turbid broth cultures to new culture material by means of the
platinum loop, whereas Klein’s bacillus could not be thus conveyed.
For the bacillus described in the present paper the following name is
proposed: _Bacillus putrefaciens_.