Your-someone else's: who lives in our body, and why we need them
Bacteria are our friends. Honestly. Most of them, anyway. It may be difficult for us to talk about these microorganisms as something good, but our body, especially the intestines, need them so that it can function effectively. Yes that there — according to microbiologists, we on 90% consist of bacteria! But not all "neighbors" are so good: among them, there are those with whom it would be nice to finally make friends, there are nasty, but under certain circumstances safe, and there are also quite harmful, from which one is a hassle.
The human body is home to trillions of strange and amazing life forms. Our gut alone contains about a kilogram and a half of bacteria, about four hundred different species in total. We live in symbiosis with the useful ones, they help us digest food and produce enzymes that we use to digest the necessary nutrients. Others produce potentially harmful toxins, and if their population is not constantly contained, then you can expect trouble. The balance in one direction or another depends on diet, age, stress, periodic alcohol consumption, and a number of other factors.
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Everyone is terribly afraid of E. coli, and rightly so. For example, some strains of it (such as O157: H7) cause severe diseases and even lead to the death of the elderly, young children, and people with weakened immune systems. However, other strains are part of the normal intestinal flora of humans and animals. Escherichia coli benefits the host body, for example, by synthesizing group K vitamins (necessary for the synthesis of proteins that provide a normal level of blood coagulation), as well as preventing the development of pathogens in the intestine.
Or take Salmonella, the well-known pathogens of food poisoning, which live happily on our skin without any harmful effects on us. We have a lot of animals on our skin. Bacteria associated with sweat glands and hair follicles are especially abundant. They can sometimes cause acne, but with a healthy immune system, they do not harm us. Staphylococci, pneumo-and streptococci, pathogens of angina, meningitis, pneumonia, and other unpleasant infections constantly live on the mucous membrane of the nasopharynx. The mouth is home to a bacterium from the genus of treponemes, which does not cause harm to a healthy person, but to those who do not follow the hygiene of the oral cavity causes a lot of trouble. Its relative is the causative agent of syphilis.
The bacterium Helicobacter pylori, which infects various areas of the stomach and duodenum, is not afraid of gastric juice and feels great in the digestive system. Many cases of ulcers of these organs, gastritis, duodenitis, stomach cancer, and some cases of gastric lymphoma are associated with this infection. But for most healthy people, it is safe.
A lecturer at the Cork Institute of Technology in Ireland, Dr. Roy D. Slyator spent years studying our roommates. He quite seriously claims that the bacteria that live in the human body are a separate organ, as important as the liver. This bacterial-human interaction is mostly symbiotic: in exchange for food and nutrition, bacteria help digestion, produce vitamins, and strengthen our innate immune system. They protect us from infection by pathogens — the so-called harmful bacteria. Animals and humans that do not have bacteria or have a reduced population (due to antibiotic treatment, for example) are much more susceptible to infection.
We can't completely destroy all harmful bacteria, but usually the number of friendly microorganisms in our body is several times greater. However, sometimes force majeure happens and the balance changes. Guarding this delicate balance is the immune system, which is two-thirds made up of friendly intestinal bacteria. Each person contains about 500 different types of unicellular. They multiply to form about 100 trillion individual cells, which is much more than the several trillion human cells that make up a single person. We are really only 10% of our body, and the rest is our single-celled "neighbors".