No matter where we are, we are surrounded by countless living things that are invisible to the human eye. Some of them can be seen as true friends, others as mortal enemies. Who or what am I? These are bacteria, yeasts, fungi and other life forms that are often called "microorganisms" because these small creatures can only be seen with a powerful microscope.
Bacteria are everywhere: in the air, in the water, in the soil and in living things. It can affect or change almost any element on the earth's surface. In fact, even the smartest chemist feels green with envy and helplessness because of his ability to induce chemical change.
Not curious to know more about bacteria? Let's look at them, examine their way of life, find out why they die, and discover their usefulness to people and the problems they sometimes cause.
A varied diet
Basically, food serves a dual purpose for all living organisms. It provides the substances necessary for cell growth or renewal and produces energy. As small as they are, bacteria must also feed and eliminate waste. You have access to an infinite number of foods.
Some live a truly "ascetic" life and settle for a low price: the simple elements of carbon dioxide and nitrogen in the air. Others are more difficult to satisfy and require carbohydrates and ammonia or more complex nitrogen molecules, such as amino acids. Others are even more demanding; You need vitamins.
Humans and animals get their energy through the oxidation of foods such as sugar and fats. Breathing provides oxygen so that these "fuels" can be oxidized or burned in the body. Many bacteria, called "aerobics", also consume oxygen from the air. The energy thus obtained is released in the form of heat or stored in small molecules (such as ATP [adenosine triphosphate]). These compounds in turn serve as an energy source and burn the many chemical reactions that occur in bacterial cells. Did you know that it is one of these aerobics (Acetobacter aceti) that turns wine into vinegar?
With other bacteria, the oxidizing or combustible agent is not oxygen but various mineral compounds. For example, some nitrates and sulfates use for this purpose and convert them to nitrite, nitrogen or hydrogen sulfide, a gas that can be easily recognized by a bad odor and resembles rotten eggs. This type of bacteria that lives in the absence of oxygen is called "anaerobic." Some of the microorganisms present in the gut belong to this group.
Some bacteria still behave differently. In your case, an organic molecule plays a role similar to oxygen. The resulting process is called fermentation.
In fact, these categories of bacteria are somewhat vague, because while some species use only one of these agents to generate energy, many others are adapted to the environment and can be aerobic (requiring oxygen) and anaerobic (independent of oxygen). .
In all the above examples, energy derives from changes in chemicals in the atmosphere or environment where the bacteria live. But it's not always like this. In a way, some bacteria can be compared to plants because they get their energy from the sun through photosynthesis. They contain pigments that fix the sunlight and make it a substance that provides energy.
Waste: hazardous or useful?
As bacteria grow, they produce substances that can often be considered as metabolic waste or by-products. Toxins that are highly toxic to humans should be included in these wastes. Have you heard of tetanus disease? It is caused by the tetanus bacillus which, when it enters the body through a wound, begins to produce tetanus toxin, which spreads through the body and reaches the nervous system. The result is almost always fatal.
Another bacteria (Clostridium botulinum), Bacillus botulinus, very resistant to heat, is sometimes found in poorly sterilized cans or sweets. It releases an extremely potent toxin in the digestive tract which ultimately affects the nervous system and causes paralysis. This poison, the most toxic substance known, is two million times more potent than arsenic. Eating contaminated food can be fatal. It's so toxic that scientists estimate that just 100 grams (3.5 ounces) of this substance would be enough to wipe all human life out of the soil!
Now you can understand why you have to be extra careful when cooking. Of course, you should also throw away canned foods that have not been properly heated or sterilized. Beware of protruding cans, as Bacillus botulinus is a gas generator (anaerobic) or smells bad when opened!
Fortunately, not all bacteria are equally dangerous. Among the bacteria that use fermentation as a source of energy, they release a lot of waste that is useful to humans. For example, did you know that the distinctive smell of butter is due to the oxidation of acetoin, a bacterial byproduct that turns into pleasant smelling diacetyl? Likewise, two lactic acid bacteria (Streptococcus thermophilus and Lactobacillus bulgaricus) produce yogurt, a fermented dairy product originating in Bulgaria that is mainly consumed in Europe and North America. In the case of kefir, which is native to the Caucasus, and koumiss, which is common in Central Asia, both drinks result from the fermentation of milk by lactic acid bacteria in combination with the fermentation of milk with alcohol.
The same goes for cheese. Lactic acid, a by-product of sugar metabolism, acidifies milk and causes it to stop. Other microorganisms, usually bacteria or molds, produce a large amount of residue which gives many existing cheeses their distinctive taste and smell.
Extremely productive
Usually bacteria multiply by dividing, which means they divide into two parts. When a bacterium becomes large enough, it divides and creates two new bacteria that are identical to the mother cell. These two bacteria are in turn divided, and so on. This phenomenon occurs at regular intervals, the time required varies greatly from one species to another and depends on environmental conditions. For example, in perfect condition, a marine bacteria called Pseudomonas natriegens divides every ten minutes, while the tuberculosis microbe (Mycobacterium tuberculosis) divides only every 27 hours.
To illustrate the speed of reproduction and possible consequences, let's take a look at a single bacteria that receives the right temperature, humidity, and nutrition, and breaks down every 20 minutes, as do many bacteria in the human gut. Do you have any idea how many bacteria there would be if there were 24 hours of continuous breeding? No less than 47 x 1020 or 47 followed by 20 zeros! Even if a bacteria weighed only about half a billionth (US) of a milligram (1 milligram = 0.00003527 ounces), the result would be a mass of bacteria weighing 2,300 tons (2,500 US tons). Fantastic! Lower temperatures almost prevent bacterial growth.
It's no wonder that foods like candies, dairy products, and sauces can quickly fill with bacteria and are not suitable for consumption if not stored in a cold place. Because they are rich in nutrients, they are excellent breeding grounds for bacterial growth. One bacteria is enough to contaminate any food.
When there is no food, the temperature is inconvenient, and no residue or by-product of bacterial growth is removed, division decreases and eventually stops. Weaker bacteria die, while the rest wait for better conditions. Some, well equipped to survive, form "spores" that are very resistant to heat, drought, sunlight and disinfectants. The spores can survive for several years, and some (like botulism spores) can withstand boiling water for up to eight hours. As soon as favorable living conditions are restored, the shoot germinates into a bacterium resembling a spore and reproduction continues.
More good than bad
This brief study of the life and death of bacteria shows that while these microorganisms can sometimes be our deadly enemies, they are in most cases our precious allies. It just keeps them in check. Yes, bacteria represent their almost invisible but important world. They contribute to important natural cycles. In fact, the life and death of bacteria are of utmost importance for the balance between plant and animal life on earth. These infinite life forms therefore testify to the Creator's wisdom of all things great and small.