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Pigment production and chemical reactions.—Produces no pigment. Decomposes broth with the
evolution of a strong putrefactive odour. No such change noted in other media. Does not give the
indol reaction.
Relations.—Belongs apparently to the group of bacilli included formerly under the term
'Bacterium termo.' Resembles in many respects Proteus mirabilis, but as a rule liquefies far more
slowly and only occasionally throws out "swarming islands."
Bacillus cloacae fluorescens.
Source.—Found in Homerton sewage and sewage from St. Bartholomew's Hospital.
Form and arrangement.—Motile rods, on an average twice as long as broad, though some are
longer. Breadth 0.6 to 0.75 µ, length 1 to 2 µ, the average being about 13 µ. The rods are sometimes
attached in chains.
Motility.—Actively motile.
Growth on gelatine—Gelatine plates.—Minute colonies first become visible in 24 hours. In two
days the surface colonies have begun to liquefy and are circular, 2 to 2½ m.m. in diameter, and under
the microscope are seen to have a very delicate transparent irregular spreading margin not yet liquefied.
The circular liquefied portion is turbid with a granular deposit in the centre, and shows slight but
distinct greenish fluorescence. On the third day liquefaction has advanced so far that the colonies are
5 or 6 m.m. in diameter and partly fused with one another, the whole plate being largely liquefied
with bright yellowish green fluorescence and a sour and unpleasant smell.
Gelatine stab cultures.—Growth occurs almost entirely at the surface, along the depth of the
needle track hardly any is to be seen. Liquefaction begins at the surface on the second day, in a cone
some 2 m.m. wide at the surface, extending down some way along the needle track. It gradually spreads,
chiefly at the surface, till it reaches the walls of the tube in seven days, by which time slight
fluorescence is visible. In a fortnight the gelatine is liquefied for 10 or 12 m.m. from the surface, and
spreads downwards in a horizontal plane; the liquefied portion has a yellowish green fluorescence and
is floored with whitish deposit.
On agar-agar.—No growth occurs at 37° C.
Agar-agar streak cultures at 20° C.—Growth is rapid, a greyish-white semi-trail-lucent streak
appearing in 24 hours about 2 m.m. wide and with irregular edges. Fluorescence is first perceptible on
the second day when the streak is 8 m.m. wide. In eight days the agar-agar exhibits a brilliant
greenish-yellow fluorescence, the growth itself being whitish and semi-opaque, and from 4 to 5 m.m.
in width, with irregular wavy edges. The brilliant fluorescence persists for several weeks without fading.
On potato.—Grows as a dirty brown layer, spreading from the line of inoculation.
In broth.—Grows rapidly, giving rise to dense turbidity. A thin film forms at the surface, and
the top layer of the broth acquires in time a marked greenish fluorescence. The sediment eventually
becomes of a pale brown colour.
In milk.—Growth is similar to that of B. Jluorescens stercoralis, but slower. No coagulation is
produced, but after four days the upper layer becomes slightly yellowish and less opaque, owing to
gradual digestion.
Temperature.—No growth whatever at 37° C. Grows well at 20° C.
Rapidity of growth.—Grows rapidly, attaining its maximum in a week or ten days.
Spore formation.—Not observed.
Need of oxygen.—Growth exceedingly scanty away from the surface. Oxygen seems necessary
for the production of the fluorescent pigment.
Gas production.—Not observed.
Relation to gelatine.—Liquefies at first rapidly, later with increasing slowness.
Pigment production.—Produces a greenish-yellow fluorescent pigment, apparently allied to that
yielded by B. pyocyaneus. No pyocvanin can be extracted by chloroform from agar-agar or gelatine
cultures.
Relations.—Closely allied to B. pyocyaneus, but differing from it in its inability to grow
at 37° C.
Bacillus fluorescens stercoralis.
Source.—Found in Homerton sewage and Barking sewage.
Form and arrangement.—Motile rods, about twice as long as broad, but of variable length.
The breadth varies from 0.5 to 0.7µ, and the length from 0.8 to 1.6µ ; longer forms rarely occur.
Motility.—Actively motile.
Growth on gelatine.— Gelatine plates.—Tiny circular colonies are visible under the microscope in
19 hours. In 24 hours they are visible to the naked eye. I11 two days the surface colonies are
liquefied and appear as uniformly turbid circles 2 to 3 m.m. in diameter, with a whitish flocculent
deposit at bottom. The deeper colonies are white, spherical and still very minute. In three days the
colonies have increased in diameter up to 10 m.m., and are fused in places, the plate being mostly
liquefied with distinct greenish yellow fluorescence and a sour fecal smell. On the fourth day the
plate is completely liquefied and the fluorescence brighter.
Gelatine stab cultures.—In 19 hours there is already liquefaction at the surface as a small flat
hemisphere 2 m.m. in diameter, which in two days attains a diameter of 6 or 7 m.m., and in three
days reaches the walls of the tube, though not to a greater depth than 3 m.m. Little growth occurs
along the needle-track, growth being practically confined to the surface. The liquefaction advances
always in a horizontal plane, no cone being formed even at the first. In five days it extends 6 or
7 m.m. down the gelatine, and in a week about 12 m.m.; after this it progresses more slowly, and in
17 days has only advanced 25 m.m. from the surface. Greenish fluorescence is marked in the liquefied
portion by the fifth day, a thin pellicle forms on the surface, and there is a thick whitish deposit at the
bottom of the liquefied portion.