Bacteria in Daily Life

by Grace C. Frankland

A striking instance of the advantages of taking stock, so to speak, of the attributes of bacteria will occur to everyone in the revelation which has followed of their powers to solve one of the most knotty problems of the day—the efficient manipulation of those vast subterranean rivers of sewage which honeycomb every city of the world.

The purification which sewage underwent by passing it through the pores of the soil, or, in other words, by filtration, was recognised about the year 1870, soon after the Rivers Pollution Commissioners had begun to make their classical investigations on the land treatment of sewage; but although the rapid transformation of ammonia into nitrates which followed the passage of the sewage through a few feet of soil was noted, yet the mechanism of this nitrification process remained a mystery until 1877, when two French chemists—MM. Schloesing and Muentz—made the then astounding discovery that this change was dependent upon the vital energies of micro-organisms.

The part played by bacteria in the purification of sewage thus became an established fact, and the later experiments have been devoted to studying the necessary conditions under which the maximum amount of work is obtainable from these novel bacterial labourers.

Two different classes of bacteria are required to carry on the purification of sewage: those which flourish in the absence of air and are known as anaërobic bacteria, and those to which the presence of air is essential for the exercise of their functions, the latter being therefore called aërobic bacteria.

The work of the anaërobic labourers consists in breaking down the complex organic compounds present in sewage, whilst the completion of the process of purification is left to the aërobic varieties. In the ordinary course of nature both these processes are going on side by side, but it has been found advisable to separate these two different classes of bacteria as far as possible, and allot distinct premises to the anaërobic and aërobic varieties respectively engaged in the purification of sewage, for by so doing experience has shown that the work is not only more expeditiously, but also more efficiently, carried out.

Now the anaërobic bacteria are supplied along with the sewage, and the retention of their services offers practically no difficulty as long as an ample allowance of space and time is given them in which to carry on their labours. The aërobic bacteria, however, besides demanding space and time, insist upon their workshops being well ventilated, and if the supply of fresh air is in any way curtailed they stop work entirely. Hence the ventilation of the aërobic workshops becomes a matter of primary importance if the valuable services of these labourers are to be retained. To ensure a sufficient supply of air being provided, it has been found advisable to have two or more aërobic workshops or bacteria contact beds, and the sewage is passed from one on to a second, and so on, until the purification is complete. Under proper management the sewage should leave the works as an inodorous, almost pellucid liquid, incapable of putrefaction, which may be turned into rivers or other waterways without fear of rousing the wrath of local riparian authorities.

But whilst the commercial side of bacteriology, so to speak, has made such great strides, the purely scientific applications which have been made of the facts it has furnished have by no means lagged behind. Chemists, from Pasteur downwards, have made use repeatedly of special bacteria to perform delicate operations in the laboratory which other methods have either failed to accomplish or have performed in a clumsy and less expeditious manner.

There can be no doubt that, as our knowledge grows from day to day, we shall find more and more how much depends upon the work of individual bacteria, and how much importance attaches to the selection of just those varieties which are of value, and the banishment of those which are detrimental; and thus the many applications which bacteria already admit of render their easy access a matter of increasing consequence, enhancing the value of bacterial institutions such as already exist on the Continent.

But whilst the easy access of bacteria for experimental and scientific purposes is of great importance to the investigator, their indiscriminate distribution would equally be a source of uneasiness and danger to the community at large. Already sensational fiction has made considerable capital out of the pathogenic microbe, and with the winged aid of penny publications it does not take long for suggestions of such kinds to spread in society and assume practical shape, and whilst the administration of bacterial poisons offers comparatively but little difficulty, their identification would be a far greater problem for experts than that presented by particular chemical poisons. To cope with this danger to the public, specimens of disease-germs from these bacterial depôts may not be supplied to applicants unless the latter can prove to the satisfaction of the director that they are connected with responsible public institutions.

In recent times, indeed, one of the most remarkable practical uses to which bacteria have been put is that of poisoning-agents on a large scale, or in other words vermin exterminators; if this new rôle for bacteria becomes extended, as no doubt it will, the law for the sale of noxious drugs and preparations will also doubtless be amended to cover the distribution of bacterial-poisons.