What is the gut microbiota (microorganisms) to human cell ratio in the gastrointestinal (GI) tract?

From the Guidelines

The ratio of gut microbiota to human cells in the gastrointestinal (GI) tract is approximately 10:1, with the microbiota outnumbering human cells by a factor of ten [ 1 ].

Key Points

• The human microbiota contains an estimated 10^14 cells, with the majority found in the GI tract [ 1 ].
• The microbial composition in the GI tract varies by location, with different species present in the stomach, duodenum, and colon [ 1 ].
• The gut microbiota is taxonomically diverse, with over 50 bacterial phyla described, and 10 phyla inhabiting the colon [ 1 ].
• The ratio of microbial cells to human cells is also supported by another study, which estimates that there are 150 times as many genes in the intestinal metagenome as in the human genome [ 1 ].

Microbiota Composition

• The Firmicutes, Bacteroidetes, and Actinobacteria phyla are the most predominant in the colon [ 1 ].
• The microbial composition in the gut lumen and the mucus layer of the GI tract also differs [ 1 ].

From the Research

Gut Microbiota Composition

• The human gut contains approximately 10^14 bacteria and other microorganisms such as Archaea, viruses, and fungi 2.
• The gut microbiota is composed of more than 1000 bacterial species, with the phyla Firmicutes, Bacteroidetes, Proteobacteria, and Actinobacteria being the most abundant 3, 4.
• Firmicutes and Bacteroidetes constitute 70-90% of the total abundance of the gut microbiota 3.

Gut Microbiota to Human Cell Ratio

• The number of microorganisms in the human gut exceeds the number of body cells by a factor of ten 2, 5.
• This means that for every human cell, there are approximately 10 microbial cells in the gut.

Stability and Variability of the Gut Microbiota

• The composition and functions of the gut microbiota are stable over long periods but can be influenced by factors such as genetics, mode of delivery, age, diet, geographic location, and medical treatments 4.
• The gut microbiota has a unique composition for each individual, although more than 95% of individuals can be assigned to 4 major phyla 2.