Bacteria are microscopically-small single-celled living organisms. Different kinds of bacteria exist on virtually every spot on earth and in every living space. Bacteria also exist in and on people - approximately 1014 varying types. If one were to write the number out, it would be a 1 with 14 zeros, ten times the amount of cells a human being has.


Most of these bacteria are useful and essential to our survival. Below we will introduce you to the most important of these “helper bacteria”. Dating back to the time when bacteria were considered plants, such accumulations of bacteria are called flora. A flora usually includes other microorganisms as well, e.g. fungi or mites.


99% of the bacteria inhabiting the human body live in the intestines. These bacteria belong to at least 500 different types, probably more. Two of the most important bacteria are E.Coli and the lactic acid bacteria. The flora composition differs from one section of the intestines to the other (e.g. small and large intestine).

The bacteria assist digestion and metabolism by metabolising different substances. They also supply the intestinal wall with energy and break down harmful substances. Intestinal bacteria produce fatty acids (e.g. acetic acid), which play a particularly large role. These stimulate the intestinal peristalsis, i.e. the contracting movements that move the digested food on.

An unbalanced intestinal flora can cause bloating, diarrhoea, infection and food intolerances and can affect the immune system. The intestinal flora is unbalanced when there are too few bacteria (under colonisation) or too many (over colonisation). A wrong composition of bacteria can also cause problems.  

Oral Flora

The mouth also contains a large amount of different bacteria. Their main purpose it to protect against harmful pathogens. Some of these bacteria are however damaging to teeth, particularly the types of bacteria that cause tooth decay and plaque.

Skin Flora



The microorganisms of the skin flora are also most useful. They build a barrier against pathogens. An infectious pathogen would have a hard time spreading on the skin, for the simple reason that it is already occupied. The bacteria play the role of placeholders. Furthermore the skin flora’s bacteria produce substances that make the skin slightly acidic, the skin’s acid protective cover. A further useful quality is that they break down certain waste products, e.g. flakes of shed skin and sebum.

The skin flora varies depending on the skin area. Most of the bacteria live in damp or greasy areas of the skin, e.g. armpits or on the forehead.

Under and over colonisation of the skin can lead to skin alterations, such as dandruff or acne.




The vaginal flora is mainly made up of lactic acid bacteria. As with the skin, these microorganisms play the role of placeholders. While everything is covered with lactic acid bacteria, it is hard for harmful bacteria or fungi to spread. Also, as their name indicated, lactic acid bacteria produce lactic acid. This causes an acidic milieu in the vagina that provides further protection against pathogenic bacteria.

If too few lactic acid bacteria are present, it can quickly lead to a bacterial infection (a so-called vaginosis) or fungal infections.

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