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Agar "stab" cultures.—Growth occurs all the way down the stab, and on the surface a white layer is
developed.
Agar "streak" cultures.—At 37° C. the growth is very rapid, and occurs as an abundant moist and
white layer.
Potato cultures.—A rich yellowish-brown layer quickly developes.
Broth cultures.—The growth is characteristic. In less than 24 hours, at 37° C., the broth is uniformly
turbid. Later, a heavy bacterial deposit collects at the foot of the tube. There is no distinct pellicle formation,
but sometimes an imperfect scum forms on the surface.
Phenol (0.05 per cent.) broth cultures.—The growth is the same as in an ordinary broth cultivation.
Litmus milk cultures.—The growth is extremely characteristic. Usually, an acid solid clotting of the milk
takes place in 24 hours at 37° C. Occasionally the clotting is somewhat delayed. First of all, the bluishpurple
colour changes to pink; then clotting occurs, and the milk, except at the free surface, becomes white.
Later, the redness extends from the surface downwards until the whole contents of the tube are bright red in colour.
Blood serum cultures.—An abundant white layer is quickly developed at 37° C.; there is no liquefaction.
Indol reaction.—Indol reaction is usually well marked in broth cultures kept at 37° C. for five days.
Reduction of nitrates.—In 24 hours, at 37° C., reduction of nitrates to nitrites well marked. [Broth 5 per
cent. KNO3 0.1per cent., water 94 9 per cent.]
Widal's test.—Typhoid blood serum gives a negative result.
Remarks.—Bacillus coli communis is one of the most abundant and most characteristic of sewage bacteria.
In this and a previous report it has been shown that its number may exceed 100,000 per c.c. of London crude
sewage. It has likewise been shown that it survives the processes at work in the biological filters at the Outfall
Works. Apart from its function as one of nature's scavengers, the B. coli is of great importance from the point
of view of the bacterioscopic examination of water. In the first report a photograph (plate I, figure 1) was given,
showing that even in so minute an amount as 1/100000 c.c. Crossness crude sewage, B. coli and closely allied
forms were present, and it was pointed out that a bacterial process of great delicacy exists for the detection
of pollution of water with minimal quantities of sewage.
It has been asserted that B. coli is abundant everywhere, that it multiplies outside the animal body, that
it is present in the intestinal contents not only of human beings but of the higher mammals and birds, and
that, therefore, its value as an indication of pollution of water of possibly dangerous sort is nil. The fact remains
that in crude sewage B. coli is present in numbers exceeding 100,000 per c.c., and is absent, or present in but few
numbers in a corresponding amount of a water free from suspicion of recent pollution. Moreover, if B. coli
multiplies outside the animal body under favourable conditions, it also loses its vitality under unfavourable
conditions, and we have yet to learn that the excrement of healthy, much less of diseased, mammals and birds
is altogether harmless to man.
The Bacillus coli may ba pathogenic, but can hardly be considered pathogenic in the ordinary sense of the
term. Its presence serves rather as an index of the possible presence of other and more objectionable kinds of
bacteria.
No apology is needed for describing B coli in a report dealing with the bacteriology of sewage. Its
prevalence in sewage, its relation to the proper bacterioscopic examination of drinking water, and the important
partitplayB as one of Nature's scavengers, all make it desirable to record its chief morphological and biological
characteristics. This is the more necessary as the published descriptions of this microbe are often incomplete,
and in some cases even misleading.
It will be noted that not only the presence of B. coli in the various samples of crude sewage and effluents
has been determined, but that, as well, a record has been kept of its relative abundance. Until such records are
obtained, not only as regards B. coli, but as regards many other species of micro-organisms, the usefulness of
bacteriology is restricted.
2. Bacillus Mesentericus.
Sewage variety E.
[An aërobic, non-chromogenic, actively motile, slowly
liquefying bacillus.]
Sewage variety I.
[An aerobic, non-chromogenic, actively motile, rapidly
liquefying bacillus.']
Source.
London crude sewage; gelatine plate cultures heated
to 80° C. for 10 minutes.
London crude sewage; gelatine plate cultures heated
to 80° C. for 10 minutes.
Morphology.
* Long bacilli, with rounded ends; solitary, in pairs
and long chains.
Medium-sized bacilli, with rounded ends; solitary, †
in pairs and chains.
Motility.
Actively motile.
Exceedingly rapid movement.
Spore formation.
Readily forms spores.
Readily forms spores.
Flagella.
‡ A multi-flagellated organism.
A multi-flagellated organism. ||
Temperature.
Grows well at the room temperature, and exceedingly
rapidly at 37° C.
Grows very rapidly at the room temperature, and
with great rapidity at 37° C.
* See fig. 3, Plate I.
† See fig. 5, Plate II.
‡ See fig. 4, Plate I.
|| See fig. 6, Plate II.