Bacteria—Helpful or Harmful?
By “Awake!” correspondent in France
WHEREVER we may be, we are surrounded by countless numbers of living creatures invisible to the human eye. Some of them can be regarded as true friends, others as mortal enemies. Who or what are they? They are bacteria, yeasts, molds and other life forms designated by the general term “microorganisms,” because these tiny creatures can be seen only through a powerful microscope.
Bacteria are to be found everywhere—in the air, water, soil and in living beings. They are able to act on or alter almost every element on the face of the earth. In fact, their ability to produce chemical changes makes the most ingenious chemists feel green with envy and quite powerless.
In this connection, biochemistry professor John M. Wood stated in the September 1976 issue of the French scientific monthly La Recherche: “It is widely known that microorganisms synthesize organic compounds more easily and efficiently than our best industrial chemists.” He also noted that bacteria are able to cause chemical reactions while “breaking long-established rules of organic chemistry.” How frustrating for the chemists!
Are you not curious enough to learn a little more about bacteria? Let us take a close look at them, peering into their way of life, finding out what causes them to die and, while so doing, discovering their usefulness to man, as well as the trouble they sometimes cause.
A Varied Diet
Basically, food for any living organism serves a double purpose. It provides substances necessary to the growth or renewal of cells, and it produces energy. Minute as they may be, bacteria also need to eat and throw off wastes. They draw upon an infinite variety of foods.
Some lead a really “ascetic” life, contenting themselves with dull fare: the simple elements of carbon dioxide and nitrogen from the air. Others are harder to please and require carbohydrates and ammonia, or more complex nitrogen molecules, such as amino acids. Still others are even more fussy; they need vitamins.
Both men and animals draw their energy from the oxidation of foods like sugars and fats. Breathing supplies oxygen so that these “fuels” oxidize or burn in the body. Similarly, many bacteria, called “aerobes,” use oxygen from the air. The energy so obtained is released as heat or stored in small molecules (such as those of ATP [adenosine triphosphate]). These compounds, in turn, serve as a source of energy, powering the many chemical reactions that take place inside bacterial cells. Did you know that it is one of these aerobes (Acetobacter aceti) that causes wine to turn into vinegar?
For other bacteria, the combustive agent or fuel is not oxygen but various mineral compounds. For instance, some use nitrates and sulphates for this purpose, transforming them into nitrites, nitrogen or hydrogen sulfide, a gas easily recognizable by its foul smell, resembling that of rotten eggs. This type of bacterium, living in the absence of oxygen, is called an “anaerobe.” Some of the microorganisms found in human intestines belong to this group.
Certain bacteria act still differently. In their case, an organic molecule plays a part similar to that of oxygen. The resulting process is called fermentation.
Actually, these categories of bacteria are quite loose, because, whereas some species use only one of these means of obtaining energy, many others adapt themselves to their environment and can be aerobic (requiring oxygen) at one time, and anaerobic (independent of oxygen) at another.
In all the foregoing examples, energy is derived from changes in chemicals at hand in the atmosphere or in the medium in which the bacteria live. But this is not always the case. In one respect, some bacteria can be compared to plants, for they draw their energy from the sun by photosynthesis. They have pigments that fix sunlight and transform it into a substance that supplies energy.
Wastes—Dangerous or Useful?
During their growth, bacteria produce substances that can often be considered metabolic wastes or by-products. Toxins that are very poisonous to man are to be counted among such wastes. Have you heard of the disease called “lockjaw”? It is caused by the tetanus bacillus, which, upon entering the body through a wound, starts producing tetanus toxin that spreads throughout the body, affecting the nervous system. The result is nearly always fatal.
Another bacterium (Clostridium botulinum), the bacillus botulinus, which is highly resistant to heat, is sometimes found in improperly sterilized canned food or delicatessen foods. It releases an extremely powerful toxin in the alimentary canal, eventually affecting the nervous system and causing paralysis. This poison, the most poisonous substance known, is two million times as powerful as arsenic. Merely tasting contaminated food may be lethal. It is so toxic that scientists estimate that just 100 grams (3.5 ounces) of this substance would be enough to sweep all human life off the face of the earth!
Now you can see why great care must be exercised in the home canning of foods. Also, one should without hesitation discard all canned foods that have not been properly heated or sterilized. Beware of any can that bulges, as the bacillus botulinus is a gas former (anaerobic), or that smells bad when you open it!
Fortunately, not all bacteria are so dangerous. Among the bacteria that use fermentation as a source of energy, many release wastes that are helpful to man. Did you know, for instance, that the characteristic odor of butter is due to the oxidation of acetoin, a bacterial by-product that turns into pleasant-smelling biacetyl?
Among many other good things, God has provided for mankind “wine that makes the heart of mortal man rejoice.” (Ps. 104:15) Taken in moderation, wine is a pleasant and healthful drink. Well, did you know that the alcohol in wine is produced by a yeast called Saccharomyces cerivisiae? Although this is not a bacterium, but a fungus, the metabolism involved is the same. From this microorganism, alcohol is a by-product resulting from the breaking down of the sugars contained in grapes.
Likewise, two lactic bacteria (Streptococcus thermophilus and Lactobacillus bulgaricus) produce yogurt, a fermented milk product that originated in Bulgaria, and is mostly eaten in Europe and North America. As for kefir, originally from the Caucasus, and koumiss, common in Central Asia, both are drinks resulting from the fermentation of milk by lactic bacteria coupled with an alcoholic fermentation of the milk by yeast.
The same applies to cheese. Lactic acid, a by-product of the metabolism of sugars, acidifies milk and causes it to curdle. Other microorganisms, often bacteria or molds, produce a whole range of wastes giving the many existing varieties of cheeses their distinctive taste and smell.
Extremely Prolific
Generally speaking, bacteria reproduce by fission, which means that they split in two. When a bacterium reaches a sufficient size, it splits, resulting in two new bacteria identical to the parent cell. In turn, these two bacteria split, and so on. This phenomenon occurs at regular intervals, the time required varying greatly from one species to another, and depending upon environmental conditions. For example, if it is placed in ideal conditions, a marine bacterium called Pseudomonas natriegens splits every 10 minutes, whereas the tuberculosis microbe (Mycobacterium tuberculosis) splits only every 27 hours.
To illustrate how fast reproduction occurs and what its consequences can be, let us consider a single bacterium provided with the right conditions of temperature, moisture and food supply, and splitting every 20 minutes, as is the case with many bacteria found in human intestines. Do you have any idea of the number of bacteria there would be if reproduction continued uninterrupted for 24 hours? No fewer than 47 x 1020, or 47 followed by 20 zeros! Although a bacterium weighs only about half a billionth (U.S.) of a milligram (1 milligram = .00003527 ounce), the result would be a mass of bacteria weighing 2,300 metric tons (2,500 U.S. tons). Amazing! Lower temperatures impede nearly all bacterial growth.
No wonder foodstuffs such as delicatessen foods, dairy products and sauces can be quickly overgrown with bacteria and can become unsuitable for consumption if not stored in a cold place! Being rich in nutrients, they are excellent culture media for bacterial growth. Just one bacterium is enough to contaminate the whole food item. How forceful and accurate was the apostle Paul’s illustration, “A little leaven ferments the whole lump”!—Gal. 5:9.
When food is lacking, when the temperature is unfavorable and when the wastes or by-products of bacterial growth are not removed, splitting slows down and eventually stops. The weakest bacteria die, while the others wait for better conditions. Some, well equipped for survival, form “spores,” which are very resistant to heat, dryness, sunlight and disinfectants. Spores can survive for years, and some (for example, the botulism spore) can withstand boiling water for eight hours. As soon as favorable life conditions are restored, the spore germinates and develops into a bacterium similar to the prespore one, and reproduction resumes.
Vulnerability
Having considered how bacteria live and multiply, let us now see what causes them to die.
Microorganisms are sensitive to many physical or chemical agents. These agents are said to have a “bacteriostatic action” when they stop the growth of bacteria, and a “bactericidal action” when they kill them.
The sun, with its ultraviolet rays, is doubtless the oldest bactericidal agent, and one of the most efficient. Ultraviolet rays bring about mutations in bacteria, that is to say, changes in their genetic makeup, which prove to be deadly in most cases.
In general, bacteria are unable to develop in highly concentrated solutions of substances like sugar or salt. In such conditions, the water contained in the microorganisms is released through the cell wall in an attempt to dilute the medium outside (osmosis). The result is that the bacteria dehydrate and stop growing or die. This is what occurs when meat or fish is salted. Similarly, the presence of a large quantity of sugar in fruit jellies or jams helps to preserve them.
Heat is bacteria’s mortal enemy. A temperature of 50 to 60 degrees Celsius (122 to 140 degrees Fahrenheit) for half an hour is sufficient to neutralize most bacteria, but those that can form spores require more stringent measures. It takes 20 minutes in a steam sterilizer to kill such germs. For this reason a surgeon’s gown and the drapes over his patient are sterilized in such a manner.
Bacteria also are sensitive to many chemical substances. Knowledge of this can be put to good use in various ways, for example, in food preservation. The oldest and best-known chemical preservatives doubtless are alcohol and vinegar. More recently the chemical industry has created a wide variety of products acting either on bacteria or on fungi, and preventing their growth. Some of these chemical agents seem to be harmless, but unfortunately the long-term secondary effects of many of them are not known.
Antiseptics, too, are chemical products that are detrimental to bacteria. They are useful for disinfecting skin, clothing or rooms. Housewives knowingly or unknowingly wage war on bacteria when they use kitchen disinfectants, bleaches, iodine, carbolic acid and hydrogen peroxide.
Finally, among bacteria’s enemies mention must be made of antibiotics, which, when used correctly, are extremely useful in combating certain infectious diseases.
More Good than Harm
This short study of the life and death of bacteria reveals that, although such microorganisms can sometimes be our deadly enemies, more often than not they are our precious allies. It is simply a question of keeping them under control. Yes, bacteria represent an almost invisible but important world of their own. They contribute to the indispensable natural cycles. Indeed, the life and death of bacteria are of utmost importance to the balance of plant and animal life on earth. These infinitesimal life forms therefore testify to the wisdom of the Creator of all things, great and small.