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36
Litmus milk cultures.
In 24 hours at 37° C. slight discolouration has taken
place. In 48 hours the liquid is of a dirty yellowish-white
colour, with a tinge of red ; no clot. In 72 hours a weak
clot has formed, and the liquid near the surface is semitransparent.
On gently shaking the tube, a pinkish
tinge develops. In five days the clot lies at the foot of
the tube as a dirty white mass; above this the liquid is
transparent and of a faint yellow colour, which on
shakintr changes to a pink tint.
In 24 hours at 37° C. the bluish-purple colour of the
milk is changed to a dirty yellowish-white; no clot.
In 48 hours no clot, but the milk is rapidly becoming
transparent. In 72 hours the whole of the contents of
the tube are semi-transparent and of a dirty yellowish
colour. On gently shaking the tube, the liquid assumes
a crushed strawberry colour.
Blood serum cultures.
At 37° U., and in less than 24 hours, nearly the whole
of the oblique surface of the medium has become covered
with a deeply wrinkled skin. Later, slow liquefaction
sets in, and in about 16 days the blood serum is completely
liquefied.
At 37° C. decided liquefaction takes place in less than
24 hours, and on the surface of the liquid, at the foot of
the tube, a wrinkled skin is formed. Later, the blood
serum is completely liquefied.
Indol reaction.
No indol is formed.
No indol is formed.
Reduction of nitrates to nitrites.
[Broth 5 per cent., KNO3 0.1 per cent., water 94.90 per cent.]
Great reduction of nitrates to nitrites in 24 hours at
37° C.
No reduction of nitrates to nitrites in 24 hours at
37° C.
Remarks.
Resembles very closely, if it is not identical with,
Bacillus mesentericus ruber.
The micro-organism is constantly present in sewage
in the form of spores; 10, 20, 30, or more spores per c.c.
of London crude sewage may be found. It is present in
considerable number in the effluents from the biological
filters. It resembles closely B. mesentericus vulgatus,
B. mesentericus fuscus, and B. liodermos, and is perhaps
most closely allied to, if it is not identical with,
B. mesentericus vulgatus.
3.—Sewage Proteus.
[An aerobic, non-chromogenic, actively motile, rapidly liquefying bacillus.]
Source.—Very abundant in London crude sewage; frequently as many as 100,000 per c.c. of crude sewage.
Morphology.*—Small bacilli, with rounded ends; solitary, in pairs, or sometimes in short chains; involution
forms may occasionally be seen.
Motility.—Actively motile.
Spore formation.—No spores are formed.
Flagella.†—Each rod is possessed of a single flagellum.
Temperature.—The original culture grew better at 20° C. than at 37° C.¶
Gelatine plate cultures.‡—In less than 24 hours at 20° C. the surface colonies appear as delicate granular films
of irregular shape. In two days the colonies look like "punched out" circles containing liquefied gelatine, and
greyish-white bacterial deposit. The masses of bacteria lying in the liquefied gelatine usually give a mottled
appearance to the colonies. Viewed under a low power of the microscope the individual bacilli can be made out,
and their active movement watched: the colonies appear darkest centrally and at the circumference, and here and
there darker spots may be seen in the liquefied and granular-looking gelatine. The colonies are usually exactly
circular in shape with well-defined borders, and no swarming islands" appear to be given off, as in proteus
vulgaris. By the third or fourth day the plate is completely liquefied, the gelatine being converted into a turbid
greyish-white liquid.
Gelatine "stab" cultures. §.—The growth is very characteristic.—In 24 hours at 20° C. liquefaction has occurred
all the way down the path of the needle, and minute bubbles of gas may be watched rising through the turbid,
greyish-white liquefied gelatine to the surface. In 48 hours the liquefaction is very much more pronounced;
numerous bubbles of gas may be seen at the surface, and also bubbles in the solid gelatine. The bacteria collect
at the foot of the liquefied portion as a greyish-white deposit. In four or five days the whole of the gelatine is
converted into a greyish-white liquid. If such a culture be heated to 80° C. for 20 minutes the bacilli are killed,
but if, after cooling, a portion of the fluid be added to another tube containing solid gelatine, the gelatine in this
second tube becomes liquefied.
Gelatine "streak " cultures.—The gelatine is liquefied so rapidly that all details of growth are lost.
Gelatine "shake" cultures.—|| In 24 hours at 20° C. numerous gas bubbles are formed, and the gelatine is
liquefied near the surface.
Aqar plate cultures.—The growth is not characteristic. The colonies are more or less circular in shape,
they are greyish-white in colour, and have a somewhat moist, glistening appearance.
Agar "stab" cultures.—There is growth all down the stab; gas bubbles may form in the medium; on the
surface the growth is like a surface colony in an agar plate culture. In old cultures the surface growth becomes
of a brownish colour.
Agar "streak" cultures.—The growth is rapid, but not specially characteristic. A greyish-white layer
having a moist glistening appearance is formed, which may extend nearly to the walls of the tube.
Potato cultures.—The growth is not characteristic; a slimy, thin, yellowish-white growth appears on the
surface of the potato.
Broth cultures.—Abundant diffuse cloudy growth in 24 hours at 20° C.
Litmus milk cultures.—The growth at 20°C. in litmus milk culture may be described as an acid change from
an opaque bluish-purple coloured liquid to a semi-transparent reddish-coloured fluid. The redness is chiefly near
the surface, but if the tube be shaken the whole of the contents of the tube assume a crushed strawberry tint.
If clotting occurs, it is imperfect in character and possibly is dissolved as soon as it is formed.
Blood serum cultures.—Rapid growth, accompanied by liquefaction.
Indol reaction.—Usually no indol is formed in broth cultures, but in one such culture, kept for twelve days,
a feeble indol reaction was observed.
Reduction of nitrates.—Rapid reduction of nitrates to nitrites in 24 hours at 20° C. [Broth, 5 per cent.,
KNOs 0.1 per cent., water 94.9 per cent.]
Remarks.—This organism differs from Proteus vulgaris, and has little or no resemblance either to Proteus
mirabilis or to Proteus zenkeri. It differs from Proteus vulgaris in many respects, for example: sewage proteus
* See fig. 10, Pate III. † See fig. 11, Plate III. ¶ See, however, notes under heading, Remarks.
‡ See fig. 12, Plate III. § See fig. 13 (6) (c), Plate IV.
|| Fig. 13 (a), Plate IV.