Bacteria and digestion

The human gastrointestinal apparatus can contain on average 300-500 different species of bacteria that are jointly referred to as the “intestinal bacterial flora” (see graph). Most bacteria are located in the colon, while very few are in the stomach and in the first part of the intestine, because they contain corrosive substances (acids, bile and pancreatic secretions) which make these habitats inhospitable for micro-organisms. The colonisation of the intestine starts at birth and takes a few days (see image). The bacterial flora is composed of anaerobic and aerobic bacteria. The first group includes such bacteria as bifidobacteria, eubacteria, clostridia and peptococci. Anaerobic bacteria include, among others, escherichia, enterobacteria, enterococci, klebsiella, lactobacilli and proteus.
The intestinal bacterial flora serves different important functions:
– it protects the organisms from the attack of harmful micro-organisms,
– it breaks food into microscopic particles to supply the organism with vitamins, mineral salts and all the micro-nutrients it needs,
– it produces vitamin K, which is important for blood coagulation, the liver and bone calcification
– it produces vitamin B12, which is important for cell reproduction and the synthesis of haemoglobin
– it makes hard-to-digest foods, such as vegetables, digestible.
The bacterial flora of the intestine is weakened by some drugs, such as antibiotics. This is why antibiotic treatments are often associated with milk enzymes (which are among the main components of the bacterial flora), which restore the correct balance of these small and precious allies.

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