Bacterium

plural, Bacteria, a term meaning a little stick, applied to the lowest known form of life. We say of a toadstool that it is a lower form of vegetable life than an oak. We say of a worm that it is a lower form of life than an antelope. Still lower than the toadstool and the worm, at the bottom of the list, so far as we know, beneath all other forms of life, are bacteria. It is hard to say whether bacteria are plants or animals; probably plants, but they are exceedingly numerous and play an important part in health, growth, and disease. Every intelligent person should aim to master some of the hard names and learn what these forms are like, and why they are important.

The simpler forms of bacteria are so small that from 10,000 to 50,000 of them lying side by side are required to measure an inch. A large colony can float or swim about in a drop of water no larger than the head of a pin. Seen in water under a powerful microscope, bacteria are as colorless as the water drop, and, except from their shape, cannot be told from minute bubbles of air. Those who study bacteria have succeeded in staining them with aniline dyes so that they may be distinguished more readily. Each bacterium consists of a tiny granular mass of protoplasm, contained in, or rather, surrounded by, a membrane-like envelope.

Under certain treatment this membrane takes a deeper color than the protoplasm and may be distinguished from it. Bacteria are merely cells. They have no heads, feet, roots, or stems. They are, to all appearance, the most harmless and the most useless things imaginable.

Bacteria are of four, some authorities say three, kinds. Those of one group are globular; those of a second group are rod-like; yet another group includes slender curved or twisted forms. The individuals of all three sorts live independently of each other; very frequently they cluster together or gather end to end in lines. Some kinds even have sticky envelopes so that they cling together in jelly-like masses.

Bacteria increase in numbers in a peculiar way that has led the Germans to call them "splitting plants." Under favorable conditions of warmth and food, each bacterium develops a partition wall, and actually splits into two bacteria exactly alike and exactly like the original bacterium. If conditions be favorable bacteria will split up and split again in from twenty minutes to an hour. Supposing that we start with one bacterium and allow that splitting is to take place at intervals of an hour. We shall have two bacteria in an hour; in two hours, four; over 4,000 in twelve hours; and by the end of twenty-four hours some 16,000,000 bacteria will have sprung from a single individual. It is this power of rapid multiplication that makes them dangerous. Many kinds split slowly. Many individuals fail to get food, and in the latter case they expire or go into a state of rest and wait for better times. The form of splitting described is the simplest method observed. Some bacteria split by two cross partitions into four individuals and each of these into four again, and so on. In all cases, however, it should be remembered that the products of splitting become as large as the original bacterium and are patterned after it.

Most bacteria are provided with exceedingly slender, waving threads by which they are able to move and even dart through a drop of water. No one has suggested that bacteria have any sense or feeling, but they are sensitive, and have a faculty of rolling toward food and away from unsatisfactory conditions. All bacteria require water. Some are killed by drying an hour or two; other kinds are able to resist drouth for several days. We have not gone into the question of spores, but it will be sufficient to say that, in addition to reproduction by splitting, most bacteria may produce spores or individuals of small size in a state of rest in which they can lie over sometimes several years until moisture quickens them into activity again, when they feed and divide as before. Some species are also then capable of resisting great heat and may be boiled a long time without being killed.

Some bacteria, and it is well to understand that bacteria are known under many names, as germs, microbes, bacilli, cocci, micro-organisms, etc., cannot live without air, from which, like persons, they absorb oxygen. These are easily smothered. Others cannot live in the presence of oxygen, a good airing kills them. Others are indifferent and thrive in either case.

Each kind grows best at the temperature of its natural home. The extreme limits between which growth, i.e., multiplication, has been seen are 5 degree C., a few degrees above freezing, and 60 degree C., or three-fifths of the way to boiling water. Life may be retained outside of these limits, but not indefinitely. Many forms live through severe freezing, in the ice of ponds, etc. None are able to survive excessive and prolonged heat. Freezing water does not necessarily kill microbes. Boiling water ten minutes kills all but the most hardy bacteria. Light, too, has its effect on bacteria. Direct sunlight is hostile. Powerful electric light is as unfavorable. So-called X-rays are without effect. Of the solar rays green and violet are most fatal.

Bacteria of various kinds are found in air, in dust, in soil nine feet deep, in rain, in snow, in ice, in the water of wells and cisterns, and in the ocean, lakes, and rivers. It is difficult to get artesian water free from bacteria. They are numerous in ponds and pools containing decaying weeds or grass. They fairly swarm in water contaminated by sewage. Rotting or decaying animal or vegetable matter of every description is, as we shall see, full of bacteria. Sour milk, rancid butter, ripening cheese, decaying fruit, everything that is undergoing fermentation or putrefaction, thoroughly advertises the presence of bacteria. When we say of an article of food that it is spoiling, the chances are that bacteria are destroying it.

All bacteria live by absorbing material. A bacterium coming into contact with food suited to it, soaks in food and splits into bacteria that soak in more food and split as before. For the present purpose it is sufficient to say that bacteria feed on animal and vegetable matter. Some sorts feed on dead plants, others draw on living plants. Some feed on living animals. Comparatively few live on live plant or live animal tissue. Not all decay is due to bacteria. Chemical decomposition may take place from a variety of reasons; but in ninety-nine cases out of a hundred the rotting animal or vegetable substance is simply giving way to bacteria. We can fruit "to keep it from the air," in reality to keep bacteria out of it. We dry beef "to keep it," in reality to render it so dry and hard that bacteria cannot get a foothold. We put specimens in alcohol and formalin not only to keep them moist, but because bacteria cannot live in these liquids. We silo our cornfodder to keep bacteria out of it.

Bacteria in their right place are exceedingly useful, indeed indispensable. Straw and all that class of dressing for land, known as stable manure, would be useless, a mere incumbrance in the fields, were it not that bacteria attack it vigorously and break it up and rot it into material suitable for plant food. What we call plants, at all events field crops, would not grow, were it not that countless myriads of bacteria have manufactured plant food ready for absorption by their roots. When one passes rank grass or luxuriant vegetation anywhere, he may know that the roots of the plants are feeding where scavenger bacteria have at some time prepared food for them. Unless plants were returned to the earth and then worked over by bacteria, rank plant growth would soon use up about all the plant food available, and immense tracts now fertile would become barren. Plant life needs the help of bacteria to work over plant and animal material so that it can be used for plant food again. Animals eat plants and other animals, but plants live on air, water, and soil. Ordinarily speaking, plants cannot use old plant and animal material till it has been reduced by bacteria to soil.

Bacteria are indispensable in the arts. The retting of flax, jute, hemp, and cocoanut fiber is brought about by the action of bacteria. The gums are dissolved, leaving the fibers free. Sponges, dripping from the sea, are piled up to rot; this is to allow bacteria to consume the animal portion. Vinegar cannot be made without bacteria. The curing of tobacco is the work of bacteria. The ripening of cream and the maturing of cheese are due to bacterial action. If not allowed to go too far, butter is improved by bacteria. Nitrogen-producing bacteria, living in colonies on the roots of clover, enrich the soil. Bacteria are the great enemies of plants and animals, but they are also indispensable. We need to know how to derive profit from useful bacteria, and how to prevent harmful bacteria from doing damage.

In making war on dirt and dust, the housekeeper is fighting bacteria. Repeated examinations show that the air of a city is full of them. A greater number are found near the ground than at an elevation. Anything which raises dust increases the number of bacteria in the air. Flies carry bacteria about on their feet; bees among their hairs, and birds among their feathers. Wherever dust can lodge, there are bacteria. They flourish in dirt and filth. They cannot multiply unless moisture is present, together with some organic substance.

The modern physiologies give generous space to the subject of bacteria. Bacteria cling to the surface of the body, to clothing, under the finger nails, in the hair, in crevices or cracks of the skin. The bodies of animals and of man contain them in the mouth, stomach, and intestines; but they are never in the blood, in the muscles, glands, or any other organ or cells in the body of a healthy animal or person. There are invariably six kinds of bacteria in the mouth, although from eight to twenty-two different kinds are often found. Inflammation and soreness of the gum is usually due to the spiral bacteria of the mouth. Bacteria are, also, the cause of the decay of the dentine of the teeth. For this reason, it is highly important that the hard enamel covering of teeth be kept intact. Painful ulcers and abscesses of the roots are also caused by the activity of mouth bacteria. Mouth bacteria also give rise to a kind of poison called ptomaine. It is these ptomaine-producing bacteria that are dangerous when the skin is broken by the bite of a dog or other animal, or by the bite of a human being. They are feared by physicians almost as much as the hydrophobia bacilli of the mad dog.

In the mouth, stomach, and intestines, certain bacteria aid in digestion of foods by producing a substance called an enzyme which breaks up and liquefies solid foods, like the white of egg, and meats, and even the hard parts of vegetables.

Peculiar bacteria, to which we now come, live by breaking down the cells of living plants and animals. A living animal is made up of cells. Bones are composed of cells that are all hardened wall, no contents, we might say. The softer the part of the body, the more liquid the cell contents. Most bacteria, as we have said, are powerless to attack life. We eat, drink, and breathe them without knowing or needing to know it. But there are a few bacteria or microbes or bacilli, as we choose to call them, that attack living cells with energy,--bacteria whose presence is dangerous. It is one of the most marvelous discoveries of the nineteenth century that many fatal diseases are due to nothing more nor less than the presence of immense colonies of bacteria that turn the sick person's body into waste until death ensues. It is thought quite possible that a person in perfect health and spirits can not be taken possession of by any of these bacteria, but there are few persons who are not liable, at some time, or in some weak spot, to be seized by one disease or another.

It is the theory of modern medicine that each contagious or infectious disease is the working of some particular bacterium peculiar to that disease. Consumption, or tuberculosis, as it is called more accurately, is the work of a kind of bacterium that breaks down the cells of the lungs. The dread bacteria of leprosy attack a person's extremities and literally consume their victims inch by inch. The list of diseases caused by bacteria is not short. The bacteria of disease are usually, but not always, of the rod-shaped group called bacilli in the plural and bacillus in the singular. We have accordingly the bacillus of pneumonia, the bacillus of tuberculosis, of leprosy, of glanders, of lockjaw, of syphilis, of typhoid fever, of dysentery, of diphtheria, of ulcers, of the bubonic plague, and of other diseases. The bacterium of cholera is a peculiar member of the spiral group. To say that a disease is contagious is to say that the bacilli of one person are likely to be transferred to another person and reestablish themselves in dangerous numbers.

Fortunately the membranes covering all parts of the human body, inside as well as outside, are not suitable lodging places, hosts, we say, for bacteria. The bacterium of disease needs to come in contact with fresh, living cells to gain a hold. The disagreeable pus that is found in wounds is a bacterial product. If a cut or wound be made without introducing bacteria and bacteria be kept out, no pus can form. Surgeons sterilize their instruments, boil them, wash their hands in hot water, use sterilized towels and lint, and even refrain from breathing into an incision lest bacteria be introduced. If bacteria be kept out, a cleanly cut will heal rapidly without ulceration or inflammation. It is not the surgeon's knife that is to be feared, but the bacteria.

A large part of modern medicine consists in efforts to prevent disease, to protect people from bacteria. Boards of health guard our water supply that we may not drink typhoid germs. Streets and alleys are ordered cleaned that they may not breed fever bacilli. Cleanliness is one of the laws of health. The cure of contagious diseases is sought by establishing conditions under which the bacillus ceases to thrive and degenerates or disappears from the system.

See Surgery; Medicine; Disease; Yellow Fever; Clover; Wine; Cheese; Molds; Fungus; Yeast; Canning; Silo; Cold Storage; Glanders; Lock-Jaw; Consumption; Pasteur; Koch