Revised Estimates for the Number of Human and Bacteria Cells in the Body

By R. Sender, Shai Fuchs, Ron Milo. bioRxiv, 2016

4,512 citations recorded by the source corpus.

We critically revisit the “common knowledge” that bacteria outnumber human cells by a ratio of at least 10:1 in the human body. We found the total number of bacteria in the “reference man” to be 3.9·1013, with an uncertainty (SEM) of 25%, and a variation over the population (CV) of 52%. For human cells we identify the dominant role of the hematopoietic lineage to the total count of body cells (≈90%), and revise past estimates to reach a total of 3.0·1013 human cells in the 70 kg “reference man” with 2% uncertainty and 14% CV. Our analysis updates the widely-cited 10:1 ratio, showing that the number of bacteria in our bodies is actually of the same order as the number of human cells. Indeed, the numbers are similar enough that each defecation event may flip the ratio to favor human cells over bacteria.

Subfields: Immunology, Molecular Biology, Physiology

View Paper: https://www.semanticscholar.org/paper/9a76fd4c97aa984b1b70a0fe99810706a226ab41

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Citations in the corpus

Human gut microbiota in health and disease: Unveiling the relationship (2022, background): “Recent studies have demonstrated that the progression of diabetes is closely correlated to the alterations in the composition of intestinal microbiota (Sender et al., 2016; Gurung et al., 2020).”
The Effects of Vegetarian and Vegan Diets on Gut Microbiota (2019, background): “” Several studies have suggested that there are three basic bacterial enterotypes (5) (1) genus Prevotella (considered to be mostly anti-inflammatory and otherwise protective), (2) genus Bacteroides (more pro-inflammatory and possibly related to the heightened risk of metabolic syndrome and other pa”
Gut Bacteroides species in health and disease (2021, background): “The human colon is the main site of habitation for bacterial residents with an estimated concentration of 10(12)/ml.(4) As the colon of the gastrointestinal tract (GIT) of mammals has the availability of diverse nutrient sources (derived from the host diet), this makes it a predilection site for num”
The Influence of Probiotics on the Firmicutes/Bacteroidetes Ratio in the Treatment of Obesity and Inflammatory Bowel disease (2020, background): “In the human body, trillions of microorganisms live in symbiosis with the host and are mainly located in the gastrointestinal tract, skin, saliva, oral mucosa, conjunctiva, and vagina [1].”
Resistance Mechanisms to Immune-Checkpoint Blockade in Cancer: Tumor-Intrinsic and -Extrinsic Factors. (2016, neutral): “Recent estimates suggest that the human cells in our bodies are outnumbered by bacteria (Sender et al., 2016), the majority of which inhabit the gut.”
Intestinal Barrier Dysfunction, LPS Translocation, and Disease Development (2020, background): “Furthermore, the number of microorganisms inhabiting the intestine or the gastrointestinal (GI) tract has been estimated to exceed 10(14), which encompasses ∼10 times more bacterial cells than the number of human cells and over 100 times the amount of genomic content (microbiome) as the human genome”
The microbiome and human cancer (2021, background): “1 to 1% are archaea and eukarya (including fungi) (27, 48).”
The healthy human microbiome (2016, background): “The ecosystem of the colon has been the most intensively studied body habitat (Table 1) as it boasts a remarkable diversity between people and a microbial biomass (cell count) that eclipses that of other body sites by more than an order of magnitude [32].”
Are We Really Vastly Outnumbered? Revisiting the Ratio of Bacterial to Host Cells in Humans. (2016, methodology): “We revisited and updated the values for all the main contributors to total cell number to find 3.03 1013 human cells in the 70 kg ‘‘reference man’’ with 2% uncertainty and 14% CV (Sender et al., 2016).”