Types
Not all the species in the gut have been identified because most cannot be cultured, and identification is difficult. Populations of species vary widely among different individuals but stay fairly constant within an individual over time, even though some alterations may occur with changes in lifestyle, diet and age. An effort to better describe the microflora of the gut and other body locations has been initiated; see Human microbiome project. In 2009, scientists from INRA (France) highlighted the existence of a small number of species shared by all individuals constituting the human intestinal microbiota phylogenetic core.
Most bacteria belong to the genera Bacteroides, Clostridium, Fusobacterium, Eubacterium, Ruminococcus, Peptococcus, Peptostreptococcus, and Bifidobacterium. Other genera, such as Escherichia and Lactobacillus, are present to a lesser extent. Species from the genus Bacteroides alone constitute about 30% of all bacteria in the gut, suggesting that this genus is especially important in the functioning of the host.
The currently known genera of fungi of the gut flora include Candida, Saccharomyces, Aspergillus, and Penicillium.
An enterotype is a classification of living organisms based on its bacteriological ecosystem in the human gut microbiome. Three human enterotypes have been discovered.
Read more about this topic: Gut Flora
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—Henry David Thoreau (1817–1862)
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—Albert Camus (1913–1960)