Major bacterial phyla represented in the human intestine
| Phyla . | Description . |
|---|---|
| Bacteroidetes | This phylum comprises aerobic and anaerobic Gram-negative bacteria, which commonly function to help break down carbohydrates. The breakdown products of carbohydrate metabolism have been shown to modify host inflammation. An example of an organism from this phylum is Bacteriodes fragilis. |
| Firmicutes | This phylum comprises Gram-positive bacteria with low levels of guanine and cytosine nucleotides. It contains bacteria that are phenotypically diverse and are able to form endospores. An example of an organism from this phylum is Roseburia hominis. |
| Actinobacteria | This phylum is primarily composed of Gram-positive bacteria with high guanine and cytosine nucleotide levels. These organisms are commonly associated with the production of secondary metabolites. An example of an organism from this phylum is Bifidobacterium bifidum. |
| Proteobacteria | This phylum is composed of Gram-negative bacteria, many of which are pathogenic to humans. In the gut microbiota of healthy individuals, Proteobacteria are classically believed to be less abundant than Bacteroidetes, Firmicutes, and Actinobacteria. However, bacteria in this phylum frequently expand in dysbiosis or other disease states. An example of an organism from this phylum is Escherichia coli. |
| Phyla . | Description . |
|---|---|
| Bacteroidetes | This phylum comprises aerobic and anaerobic Gram-negative bacteria, which commonly function to help break down carbohydrates. The breakdown products of carbohydrate metabolism have been shown to modify host inflammation. An example of an organism from this phylum is Bacteriodes fragilis. |
| Firmicutes | This phylum comprises Gram-positive bacteria with low levels of guanine and cytosine nucleotides. It contains bacteria that are phenotypically diverse and are able to form endospores. An example of an organism from this phylum is Roseburia hominis. |
| Actinobacteria | This phylum is primarily composed of Gram-positive bacteria with high guanine and cytosine nucleotide levels. These organisms are commonly associated with the production of secondary metabolites. An example of an organism from this phylum is Bifidobacterium bifidum. |
| Proteobacteria | This phylum is composed of Gram-negative bacteria, many of which are pathogenic to humans. In the gut microbiota of healthy individuals, Proteobacteria are classically believed to be less abundant than Bacteroidetes, Firmicutes, and Actinobacteria. However, bacteria in this phylum frequently expand in dysbiosis or other disease states. An example of an organism from this phylum is Escherichia coli. |