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7
Fluorescent bacteria.
The bacteria causing fluorescence do not appear to be so numerous in London crude sewage as
in samples of sewage obtained from other sources.
Bacillus Fluorescens liquefaciens, and its varieties.
Barking crude sewage.
Present in 0.00001 c.c. of crude sewage, (Expt. 2)—Absent in 0.0001 c.c. of crude sewage
(Expt. 7)—10,000 per c.c. crude sewage, (Expt. 10)—40,000 per c.c. of crude sewage (Exp. 14).
Crossness crude sewage.
Absent in 0.00005, 0.0001, and 0.0001 c.c. of crude sewage (Expts. 1, 8and Irrespectively)—
10,000 per c.c. of crude sewage (Expt. 3).
Bacillus Fluorescens non-liquefaciens, and its varieties.
Barking crude sewage.
Absent in 0.00005, 0.000l and 0.0001 c.c. of crude sewage (Expts. 2, 7 and 10, respectively.)
Crossness crude sewage.
Absent in 0.00005, 0.0001, 0.0001 and 0.0001 c.c. of crude sewage. (Expts. 1, 3, 8 and 11,
respectively).
Although it was absent in the minute quantities of crude sewage used in the above-named
experiments, B. Fluorescens non-liquefaciens is undoubtedly present in both Barking and Crossness
sewage, but is apparently not so abundant as in many other polluted liquids.
* Coli Group of Bacteria.
As well as the true Bacillus Coli Communis there are a very large number of its close
allies constantly present in Barking and Crossness sewage. Many of these resemble B. Coli so
closely as to be differentiated only by subculture in a variety of media. In an excellent paper
on "Coli and its varieties" Mr. M. H. Gordon¶ has shown how great is the number of bacteria in
nature which resemble the Bacillus Coli Communis sufficiently closely to suggest a similarity, and which
yet can be shown by subculture in various media by the application of certain tests, and by flagella
staining, to belong to separate groups, although the majority of them are phase forms of the coli species.
† B. Mycoides, ‡ B. Subtilis, and § B. Mesentericus.
The spores of these micro-organisms are commonly present in London crude sewage, as the
following notes show—
Barking sewage.
10 spores of B. Subtilis and 10 of B. Mycoides per c.c. of crude sewage (Exp. 10).—20 spores of
B. Mesentericus, 10 of B. Subtilis and 10 of B. Mycoides per c.c. of crude sewage (Exp. 14) in this
sample, ||B. Megaterium was also found.
Crossness sewage.
At least 20 spores of B. Subtilis and 20 of B. Mesentericus in 1 c.c. crude sewage (Exp. 15).
A number of other spore-bearing micro-organisms are at present under observation and will
probably be described in a further report.
Sarcinae, Yeasts and Moulds.
These are so rarely met with in cultivations of London crude sewage, that they almost suggest,
when present, the possibility of air contamination.
In conclusion, it is to be noted that a large number of bacteria, other than those already
discussed, have been met with in the cultivations of the different samples of sewage. Many of
these belong to species hitherto not described, or described in so incomplete a manner as to make
comparison and identification difficult if not impossible. It is hoped that in further reports space may
be found for the description of a few of these bacteria. As showing the great number of bacteria of
different sorts in sewage it may be stated that in a cultivation of Crossness crude sewage, containing
so minute a quantity as 0.00001 c.c. of sewage, there were present at least five distinct species of microorganisms
out of a total of 34 colonies.
* See No. 1 (Plate I.). † See Nos. 7 and 8 (Plate I.). ‡ See No. 11 (Plate I.).
§ See No 9 (Plate I.). || See No. 10 (Plate I.).
¶ Journal of Pathology and Bacteriology, June, 1897.