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Potato cultures.—A porcelain-white growth slowly developes; afterwards the colour becomes dirty
yellowish-white and the bacterial layer becomes unequally thickened.
Broth cultures.—The growth is very scanty and not characteristic.
Litmus milk cultures.—No clotting occurs, and the change in the medium is hardly visible, even after
16 days. Apparently a feeble acidity of the milk results.
Blood serum cultures.—Little or no growth on the surface, even after the lapse of some time; some growth,
however, takes place in the fluid at the foot of the tube.
Indol reaction.—No indol is formed in broth cultures.
Reduction of nitrates to nitrites.—Negative after 12 days at 20° C. [Broth 5 per cent., KNO3 0.1 percent.,
water 94.9 per cent.]
Remarks.—This micro-organism has a somewhat negative character of growth in all the nutrient media
ordinarily in use. It has been called B. fusiformis owing to the shape of the spores, spindle-shaped. So far as
could be ascertained it belongs to a new species.
6.—Bacillus Subtilissimus.
[An aerobic, non-chromogenic, non-motile, non-liquefying bacillus (? micro-coccus).]
Source.—Crude sewage.
Morphology.*—In most cultures it appears as a large micro-coccus, but if "impression" preparations be made
from surface colonies in a gelatine plate, it will be seen that at the spreading edge the elements are distinctly longer
than broad, nearer the centre they are oval and frequently united in pairs, and at or about the centre they are
perfectly spherical.
Motility.—No motility has been observed even in recent broth cultures.
Spore-formation.—None.
Temperature.—Does not grow at 37° C., but grows with extreme rapidity at 20° C.
Gelatine plate cultures.—The deep colonies are not characteristic, either on naked eye examination when
viewed with a hand-lens, or when examined under a low power of the microscope. The surface colonies are
peculiarly characteristic, and grow so rapidly and extend so widely, that a single colony may cover nearly a whole
plate in two days. The growth is film-like in character and extremely thin and transparent. It is dull grey in
colour and very faintly granular. When viewed under a low power of the microscope, the appearance is not unlike
B. coli, but the details of the growth are so much more delicate that it is difficult to perceive the slight granulation,
faint creasing and delicate veining of the bacterial film. The surface colonies are usually of a more or less circular
shape, but the spreading edge is nearly always markedly irregular.
Gelatine "streak" cultures, ‡—The growth is like an elongated surface colony. In less than 24 hours a delicate
film has spread nearly to the walls of the tube. The spreading edge is very irregular, and in older cultures may
present a terraced appearance.
Gelatine "shake" cultures.—No gas bubbles are formed in the gelatine.
Agar "streak" cultures.—A white film is formed on the surface having a markedly irregular edge. The
lateral expansion is less than in the case of gelatine cultures.
Broth cultures.—Uniform turbidity occurs in 24 hours at 20° C., and a very faint scum forms on the
surface. No motility could be made out.
Blood serum.—A thin film forms of a faint yellowish-white colour. No liquefaction occurs.
Litmus milk cultures.—No visible change in 48 hours at 20° C. Later the purple colour of the milk changes
to a reddish purple, and later still to a buff colour. On shaking the tube gently the liquid does not assume a
red tint. There is no clotting produced and no transparency of the medium occurs even in old cultures.
Indol.—No indol is formed even after 20 days at 20° C.
Remarks.—This microbe has been called B. subtilissimus on account of the thin almost gauze-like character
of the surface colonies in gelatine plate culture. No micro-organism hitherto described appears to correspond
with the above.
7.—Bacillus Subtilis.
Sewage Variety A.
Sewage Variety B.
[An aerobic, non-chromogenic, rapidly liquefying, sporeforming.
motile bacillus.]
[An aerobic non-chromogenic, rapidly liquefying, sporeforming,
motile bacillus.]
Source.
Crude sewage and effluents from coke-beds.
Crude sewage and effluents from coke-beds.
Optimum temperature.
Grows luxuriantly at 37° C., also at the room temperature.
Little or no growth at 37° C., grows luxuriantly at
20° C.
Morphology.
Large and long bacilli with rounded ends, frequently
associated in long chains.
Large and long bacilli with rounded ends, frequently
associated in long chains.
Spore formation.
Forms spores readily.
Forms spores readily.
Motility.
Waddling sluggish movement.
Waddling sluggish movement.
Gelatine plate cultures.
Forms in two days at 20° C. circular greyish-white
areas of liquid gelatine which rapidly increase in
diameter. The white masses of bacteria lying in the
liquefied gelatine may present a mottled appearance,
or may be arranged in stellate fashion. Under a low
power of the microscope (about 80 diam.) the individual
bacilli can be clearly seen in the more liquid portion,
and their movements watched. At the edge of the
colonies the bacilli bore side by side into the nonliquefied
gelatine in a highly characteristic way .‡
Rapidly froms greyish-white circles of liquefied
gelatine. The masses of bacteria lying in the liquefied
gelatine may present a rosette or star - shaped or
radiating appearance. Under a low power of the microscope
(about 80 diam.) the movement of the individual
bacilli can be clearly seen. The parallel arrangement
of the bacilli at the periphery of the colonies is absent,
or not so well marked as in the case of variety A. A
skin forms on the surface of the liquefied gelatine.
The growth is not so rapid as in the case of variety A.
Sometimes the colonies are not exactly circular in shape.
* See fig. 17, Plate V.
† Fig. 18, Plate V.
‡ Fig. B, plate VII.