Bacteria
organisms that comprise a class of low plants, the importance of which is due to their power of producing profound changes in life. The terms bacteria, germs, microbes, bacilli, are popularly used to denote these microscopic objects. Bacillus means a little rod. The term is properly applicable to only such microbes as are rod-shaped.
The word microbe (from the Greek, mikros, small, and bios, life) is a term which was coined to include all of the microscopic plants commonly included under the terms bacteria and yeasts.
Plants or Animals. --Bacteria possess characteristics of plants and animals.
They resemble animals in their common power, independent motion, and in their habit of living upon complex bodies for food. But in general form, methods of growth, and formation of threads and spores they resemble plants. Though there are hundreds of different species there are only three general formsspheres, rods, and spirals, reminding of billiard balls, pencils, and corkscrews.
There is some, though slight, variation in size. All are extermely minute and never visible to the naked eye. They BACTERIA range in size from 1-100000th to 1-3000th of an inch. Some species have the power of active motion, and may be seen moving rapidly to and fro in the liquid in which they are growing. This motion is produced by flagella, which protrude from the body. species that have been carefully watched of fours, eights, or sixteens. Some long chains; others produce solid groups remain attached after division, forming With some species the individuals tiply by simple division or fission. individual elongates the middle into similar halves; each of which then repeats the process. ates and then divides in With ion.
Each species the individuals some BACTERIA decomposition or Sometimes, however, they possess the power of building other compounds out of fr Sometimes, however, they possess the decomposition or cleavage products. industries based upon the decomposition industries in the separation of the jute, hemp, and cocoanut fiber; also in as tearing down. There are various fragments, ts, thus building up as well the commercial preparation of sponges, material in the preparation of linen, valuable fibers from the useless fibrous powers of bacteria-viz., the maceration and often in the early stages of leather remain attached after division, forming preparation. Some 50 years ago it was long chains; others produce solid groups of fours, eights, or sixteens. Some species that have been carefully watched enormous, were it not that their rate bulk and weight of which would be under favorable conditions, to grow so rapidly as to divide every half hour.
At this rate in one day each microbe would produce over 16,000,000 descendants. At the end of the third day they would number millions of millions, the bulk and weight of which would be enormous, were it not that their rate of multiplication is checked either by cause of fermentation and putrefaction. containing organic matter, and are the their own excreted products, which are injurious to them. or ferment Harmful Bacteria. - Bacteria abound in all putrescent or fermenting mixtures containing cause of fermentation and putrefaction. ng organic matter, and are the Some are present in, and the cause of, certain of the zymotic out of surgical wounds, there is no sup- in diameter, often less. If they are kept erysipelas, tuberculosis, etc. Micrococci are spheroidal bacteria, and very small, never more than 1-25000th of an inch in diameter, often less. If they are kept out of surgical wounds, there is no suppuration. The discovery of this fact made hundreds of operations possible which of old were thought to be out of the reach of art-hence the wonderful success of antiseptic surgery.
Bacillus Tuberculosis. - Very great interest attaches to the bacillus tuberculosis, which is so constantly present that it is used as a means of differentiating the inflammatory diseases of the lungs from tuberculosis. This organism always produces the disease when oculated into animals. Statistics have been published showing that the bacillus was present in 2,417 out of 2,509 cases of supposed tuberculosis. bacteria are man's greatest benefactors; Useful Bacteria. -In many respects for upon their activities is founded the continued life of the animal and vegetable kingdoms. As microbes consume the material which serves them as food they produce chemical changes therein, resulting in simpler products called found that the mysterious substance known to brewers as yeast or barm was really composed of a vast number of minute oval particles that are endowed living. plication, and, therefore, undoubtedly living. jority of butter-making countries the churned; the cream is allowed to stand for from 12 to 17 hours, thus giving the bacteria an opportunity to grow in it.
Bacteria in the Dairy. In the ma- As a result the cream becomes somecream is subjected to a process known as ripening or souring before it is the cream is churned. Not only does the ripened cream churn more rapidly the cream is churned. Not only does what soured, slightly curdled. Then As a result the cream becomes some- bacteria an opportunity to grow in it. the sweet cream, but there are develand give a larger yield of butter than the sweet cream, but there are devel- and give a larger yield of butter than what soured, slightly curdled. Then product. The dairymen in the great butter producing countries of northern Europe are making practical use of this knowledge and are utilizing pure culwhich are characteristic of the highest tures of certain bacteria which have been found to be advantageous tures of certain bacteria which have knowledge and are utilizing pure cul- Europe are making practical use of this butter producing countries of northern production of agreeable flavors. ous for the fertile soil is a class of bacteria which teria. They feed on the soil ingredients and have the same effect on the simple nitrogen cleavage products the vinegarproducing species have on alcohol-viz., Nitrifying Bacteria. - Everywhere in bringing about a union with oxygen.
Thus these nitrifying organisms form has received the name of nitrifying bacthe last link in the chain that binds the animal kingdom to the vegetable kingdom. For the nitrates are left in the soil, and may now be seized upon by the this way it will be seen that while the journey around the food cycle. In plants, by building up compounds, form the connecting link between the soil and of the cycle, by reducing them again, roots of plants and begin once more give us the connecting link between animal life and the soil. The food cycle animal life, bacteria in the other half BACTERIOLOGY would be as incomplete without the agency of bacterial life as it would be without the agency of plant life.
Aids to Digestion. The attention of investigators has been directed in modern times to a hitherto unknown class of bacteria which have a share in the process of digestion in the stomach of man and the animals. It has long been known that the mouth, throat, intestines and other organs of the human system were inhabited by harmless bacteria. It was announced by Vignal that certain other microbes found habitually in the stomach possess properties similar to that of the saliva in aiding digestion.
Numerous specimens were obtained and pure cultures made. With the artificially bred microbes a lot of experiments were tried. At least two kinds of organism were distinguished. One promoted the digestion of starch and another that of meat and albuminous substances. One acted most efficiently when it was slightly acidulated. The other needed to be a little alkaline. A third species seemed to have a special fitness for promoting the action of bile on fats.