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species of micro-organisms present in sewage.
1.—Fresh seivage Jrom, St. Bartholomew's Hospital.
From the plates made from this sewage more than 200 colonies were examined, sub-cultures
in various media being made from most of them. The following organisms were recognised—
Moulds.—One colony alone was found, of a dark brown colour, and identical with the species
found in sewer air.
Yeasts.—Four colonies of torula grew, belonging to at least two species. One species was
white and allied to common yeast (S. cerevisiae) the other was of a pale pink colour.
Micrococci.—A small streptococcus was the commonest organism present in this sewer, no less
than 37 of the colonies were referred to this species. The colonies were minute and grew slowly, so
that they formed a very inconspicuous feature in the plates. We were unable to identify the exact
species, but it possessed the power of coagulating milk in 24 to 36 hours when incubated at 37° C. It
was clearly not the common pathogenic species (Streptococcus pyogenes).
Micrococcus ochroleucus occurred twice.
Micrococcus luteus twice.
Pediococcus albus doubtfully once.
A citron coloured micrococcus which we failed to identify was met with three times.
A new species of pink coccus, which we have named Micrococcus aurora, and which we describe
later, occurred once.
Sarcina colonies were found eight times, all being of a yellow colour, though none could be
referred to the common sewer air and fresh air sarcina (S. lutea). Amongst them were S. flava and
S. aurantiaca and at least two other species which are apparently undescribed.
Bacilli.—No less than 45 colonies resembled at first sight B. coli communis, but of these less
than a dozen responded to the chemical tests (coagulation of milk, formation of gas bubbles in
gelatine shake-cultures, and production of indol in broth) which are relied on to distinguish the
bacillus from its allies. It was, nevertheless, if we except the above-mentioned streptococcus, the
commonest and certainly the most conspicuous of the organisms present in this sewage. Those of the
45 colonies which failed to give some or all of the three chemical tests must be classed, from their
morphological and cultural resemblances, as close allies of B. coli communis, but we are unable to
refer them to any described species.
B. fluorescens liquefaciens was met with twice.
B. aureus occurred three times.
B. janthinus, a brilliant violet species, occurred in one colony only.
A dark orange brown bacillus, growing rapidly, was found once.
B. subflavus and B. fluorescens aureus were each met with doubtfully once.
Proteus Zenlceri, a common putrefactive organism, occurred twice.
Bacillus mycoid.es occurred twice.
A bacillus allied to B. pyocyaneus, which we describe later as Bacillus cloacae fluorescens, occurred
twice.
A very rapidly growing bacillus, which we describe later as Proteus cloacinus, was met with once.
This species was present in all the different samples of sewage which we examined.
Cladothrix.—Cladothrix dichotoma was found once.
2.—Snow-hill sewage (Fleet sewer).
In all we examined 365 colonies in the plates made from this sewage. The variety of species
was somewhat less than in the fresh sewage from St. Bartholomew's Hospital: we recognised 15 species
as compared with 22 from the latter.
Moulds.—One colony of brown mould only grew in the plates from this sewage.
Torula—A white torula occurred several times.
Micrococci.
The streptococcus coagulating milk, mentioned as common in the St. Bartholomew's sewage, was
again very abundant here ; 22 colonies were isolated.
Staphylococcus cereus albus occurred twice.
Staphylococcus pyogenes citreus was present four times.
Staphylococcus pyogenes aureus occurred once.
Biplococcus albicans tardissirnus, eight colonies were found.
Diplococcus roseus—This organism, present also in sewer air, occurred once, and was again met
with in other sewage.
Micrococcus flavus liquefaciens—One colony only met with.
Sarcina flava occurred in 25 colonies together with three colonies of an apparently new species
of yellow sarcina, giving a characteristic sepia brown reaction with strong sulphuric acid.
Cladothrix, C. dichotoma, two colonies.
Bacilli.—Here again B. coli communis was one of the commonest bacilli present, but of the numerous
colonies which at first sight resembled it only a small proportion, a dozen or so in all, gave all the
typical chemical reactions. But it is worth noting that some of these after six to eight weeks in subculture,
while retaining the power of coagulating milk, lost the power of producing indol in broth, and
in some cases of producing gas bubbles in gelatine shake cultures. There were present a large number
of colonies of species allied to B. coli communis, which we could not identify with any already described
organism, some of these gave two of the chemical reactions of B. coli communis, but not the third.
B. mesentericus ruber was found once.
B. aureus occurred once.
Proteus cloacinus, described below, occurred twice.