Definition of microorganisms
The term can be defined as follows: A micro-organism is an organism for whose observation a microscope is needed. However, there are a few exceptions: Giant organisms such as special bacteria or unicellular eukaryotes and micro-algae visible to the naked eye1.
Microorganisms are divided into different groups: bacteria, viruses, mycosis, archaea, microalgae and protozoa. This article focuses on the former three, as they are of greater importance for the human organism:
Bacteria are unicellular organisms, which means that they only consist of a single cell. In contrast to humans and animals, they belong to the prokaryotic organisms whose cells do not have a cell nucleus. Their size is between 1 and 10 micrometers.
Viruses do not belong to the group of living organisms because they are unable to carry out an independent metabolism. They need the organelles a host cell to multiply. A virus is actually not a cell, but only a capsule with genetic information. Their size is between 0.01 and 0.1 micrometers, making them about 100 times smaller than bacteria.
Mycosis are eukaryotes, which means, among other things, that their cells have a nucleus. They are usually multicellular and consist of fungal threads (hyphae). These form a mycelium, another word for this is fungal plexus. The threads are not visible to the naked eye, only the plexus is visible to us humans without a microscope. mycosis feed either on dead organic material, live on symbiotic exchange or through the parasitic occupation of plant or animal host cells2.
Beneficial insects and pests – our microbiome
It quickly becomes clear that mycosis and bacteria in particular have beneficial but also harmful effects on the human organism. We consist of about 30 trillion body cells; if the cells of all microorganisms living on and in us are added, we come to about 39 trillion4. Our metabolism is dependent on the microorganisms that colonize us and vice versa.
It is a so-called symbiosis. The term describes the coexistence of living beings of different species for mutual benefit, i.e. a quasi win-win situation. The human microbiome influences our immune system, metabolism and hormone system3. In humans, the digestive tract, skin, nose and vagina are populated by microorganisms. Only the brain, lungs, abdominal cavity, bladder and blood are sterile11.
Classification of different microorganisms
Strictly speaking, the term microbiome includes not only the symbiotic microorganisms, but also the commensal, opportunistic and pathogenic ones. Commensal in this context means that they can be classified neither as pathogenic nor as beneficial to health. They are simply there, virtually as neutral as Switzerland. The pathogenic invisible commensals are ultimately those who harm us; they are pathogens. Opportunistic microorganisms are an in-between, because they are rather neutral most of the time, but can develop into pathogenic ones when they grow strongly from a specific number4. It is therefore obvious that we want to preserve the commensal microorganisms as well as possible and keep the number of opportunistic ones small so that no pathogenic ones develop.
The skin flora
Our skin is a complex organ that serves as a mechanical and chemical barrier to the environment. It also plays an important role as a sensory organ and in communication: we can perceive temperatures, pain or pleasant touches through our skin, it turns red when we are ashamed and pale when we feel unwell. It also regulates body temperature, produces vitamin D with the help of sunlight and is important for immune defence5:
On the surface of the skin there is a large number of microorganisms, among them are mainly bacteria, mycosis and mites. The term skin flora refers to the totality of these micro-organisms that are not pathogenic for our body6. Among them are on the one hand apathogenic ones, which play an important role for our health: They protect the body from pathogens by preventing pathogenic germs from entering the system.
On the other hand, the commensal microorganisms described above can also be found on the skin. However, these can mutate into pathogenic ones in case of a weakened immune system or skin injuries. The skin also has an acid mantle; the pH value is between 5.4 and 5.9. This is an optimal living condition for the apathogenic species that live there. The pathogenic species, however, are mainly inhibited in their growth.
In addition, the health-preserving microorganisms destroy the harmful ones. So if the former are in the majority, it is a win-win situation10. It is therefore obvious that the healthy skin flora will be promoted if its natural PH value is maintained and the skin is not exposed to any injuries. Thus, too frequent hand washing or body care with products that alter the PH value of the skin should be avoided.
If the skin is not intact, pathogenic germs can enter the organism via it. Conversely, it is also possible that harmful substances that have entered the body by other means must be detoxified via the skin. This then becomes visible on the skin surface.
The diversity of bacterial species on the skin is enormous and varies greatly depending on the location. For example, there are other co-inhabitants in moist areas such as the armpits or anal folds than, for example, on dry forearms. The bacteria feed on dandruff, sebum and sweat and their metabolic breakdown products ultimately form our individual body odour11.
Oral flora
The surface in the mouth is virtually the continuation of the outer skin, except that this is a mucous membrane that must be moist. It contains more than 700 species of bacteria and mycosis, mainly commensal and opportunistic but also pathogenic11.
The microorganisms in the mouth join together to form a so-called biofilm. This is a slime coating on our teeth, which is created when the microorganisms, together with proteins, polysaccharides and electrolytes, attach themselves to each other to form a complex structure. Only in this way is it possible for them to adhere to such a smooth surface4.
The coating contains all three forms of bacteria described in the first section. Some of the bacteria serve our health and in return benefit from our oral cavity as a habitat. This interaction is called mutualism. During the first years of life, these microorganisms are involved in the maturation of our immune system. They also keep potential pathogens away, because when they have the upper hand, pathogenic bacteria cannot spread further. An imbalance in this ecosystem can lead to disease:
Caries is a case in point. Disease therefore occurs when the composition of bacteria changes in such a way that opportunistic germs become pathogenic and gain the upper hand. According to the latest scientific findings, the main cause of diseases in the oral cavity is not too little brushing, but an imbalance in the ecological system.
It has also been found that there are enough people who practice meticulous oral hygiene but still get tooth decay. This is caused by acid-forming pests that permanently keep the pH value in saliva and within the biofilm too low4. Ideally, the saliva should be slightly alkaline, a pH value of and above 7 provides a good basis for a healthy oral flora.
Above all, an incorrect diet, which favours the proliferation of pathogenic agents, is the cause of hyperacidity in the mouth. Sugar plays a decisive role in this process: the pathogenic bacterium Streptococcus Mutans, which is normally found in the biofilm in a harmless population size, feeds on sugar. If sufficient sugar is present, it can multiply rapidly and, as a metabolic product, releases acids that can normally neutralise the complex ecosystem in the mouth. However, if you constantly consume sugar, at some point it can no longer regenerate and the acids attack the minerals in the teeth, destroy the enamel and ultimately lead to lesions in the tooth14.
How can the health of the oral flora be maintained?
From the findings in the last section it can be concluded that sugar should be consumed sparingly in the diet. This should not ignore hidden sugars in convenience food, milk, fruit and juices. An adequate fluid intake is also necessary, because dry mouth is less saliva and this is a basic requirement for the balance of the local ecosystem. Good fats like olive oil, coconut oil and aloe vera also contribute to this balance. They nourish the pellicle, the protective shield of our teeth. One can imagine a fine retina underneath, which is constantly being rebuilt, for example when it is destroyed during eating. It protects the tooth from abrasion during chewing and from acids4.
Stomach
Before the food reaches the intestines, where 99% of the bacteria that colonize us are located, it is stored in the stomach and decomposed into a pulp. Unlike the alkaline oral flora, it is acidic here, the pH of gastric acid is between 1 and 1.5, and this environment is ideal for splitting proteins and destroying bacteria12. Indeed, in 1979, the pathogenic bacterium Helicobacter pylori was discovered, which can only carry out its metabolism in the human stomach. Before that, science assumed that no microorganisms could survive this acidic atmosphere. The Helicobacter is responsible for stomach cancer; since this discovery, cases of the disease have fallen by 80% in the USA11.
Gut
The food pulp is released from the stomach into the small intestine where relatively few microorganisms are present. After macronutrients and micronutrients have been released into the human blood via the intestinal villi, indigestible carbohydrates (fibre), water, electrolytes and waste products are further released into the large intestine.
In the intestine, especially in the large intestine, there is a high number of microorganisms that perform many important tasks for us: they produce various B vitamins such as vitamin K2, are involved in sugar absorption, supply the intestinal mucosa with nutrients and produce short-chain fatty acids. In addition, they stimulate the peristalsis of the intestines, which sets the food pulp in motion, and help break down the food components and their indigestible food fibres.
For the useful intestinal inhabitants to be able to do their job for us, they would have to be fed the right food: Especially carbohydrates indigestible for our intestines keep the intestinal bacteria alive. These are also known colloquially as dietary fibres. The scientific term prebiotics is somewhat more extensive and refers to non-digestible food components that serve as food for the micro-organisms in our digestive tract11.
Vegetables and fruit contain fibre, but also cereals, seeds and nuts. The intestinal inhabitants particularly like chicory, black salsify, Jerusalem artichoke, yacon, psyllium husks and fermented foods.
Body fat storage and health depend on a healthy microbiome
Scientists have discovered that different bacteria have an influence on our body weight. For example, overweight people have clearly been shown to have an overpopulation of the Fimicutes strains. This condition seems to cause more carbohydrates to be digested and absorbed than usual. Bacteroidetes, which are associated with reduced body fat storage, count as the antagonists of the Firmicutes.
Ideally, both strains are present in a 1:1 ratio; if this relationship is out of balance, more or less sugar can be absorbed from indigestible carbohydrates, converted into body fat and stored7. For people who eat little but cannot slim, an analysis of the microbiome makes sense. In addition, these people can try to eat low-carbohydrate food for a while, and often success is already measured.
Since, as already mentioned, intestinal bacteria are involved in the production of fat cells of a healthy intestinal mucosa, their relevance for our health is obvious: our intestinal mucosa must be intact so that only that which is good for us enters our system. If the surface of the intestinal mucosa is damaged, substances enter the bloodstream and tissue, which damage us and lead to inflammation.
Conclusion
Our body is a complex ecological system. It cannot be regarded as a being consisting only of human body cells. It is rather a symbiosis between microorganisms and the human organism. Our health depends on the presence of microorganisms in a healthy balance. To achieve this, we must, above all, feed ourselves correctly. An important factor in this is to use sugar very sparingly and to consume a lot of vegetables and sufficient liquid in the form of water.
References
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5 Bütikofer, Markus; Hopf, Zensi; Rutz, Guido; Stach, Silke und Grigoleit, Andrea (2015): Humanbiologie 1: Grundlagen, Stoffwechsel und Abwehrsysteme. Zürich: Compendio Bildungsmedien. S. 135-188.
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8 Krieger, Dr. Elena (2015): Die Milchlüge: Die Milch macht's - leider doch nicht. München: CBX Verlag.
9Kahlert, Christian und Müller, Pascal (2014): Mikrobiom – die Entdeckung eines Organs. In: Schweiz Med Forum.
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