A study by Sender, Fuchs, and Milo (2016) revises estimates of the number of human and bacterial cells in the human body. The researchers found that the total number of bacteria in a 70 kg "reference man" is approximately 3.8×10¹³, while the number of human cells is about 3.0×10¹³. This challenges the widely accepted 10:1 ratio of bacterial to human cells, showing that the numbers are actually comparable, with the total bacterial mass being about 0.2 kg. The study emphasizes that the majority of bacterial cells reside in the colon, and the number of human cells is dominated by hematopoietic lineage cells. The researchers also note that the ratio of bacterial to human cells varies across different population segments, with a range from 1.3 to 2.3. The study highlights the importance of accurate estimates for understanding the role of the microbiota in human biology and underscores the need for further research to refine these estimates. The findings suggest that the human body contains roughly the same number of bacterial cells as human cells, with the bacterial mass accounting for about 0.3% of the body weight. The study also discusses the implications of these findings for understanding the human microbiome and its impact on health.A study by Sender, Fuchs, and Milo (2016) revises estimates of the number of human and bacterial cells in the human body. The researchers found that the total number of bacteria in a 70 kg "reference man" is approximately 3.8×10¹³, while the number of human cells is about 3.0×10¹³. This challenges the widely accepted 10:1 ratio of bacterial to human cells, showing that the numbers are actually comparable, with the total bacterial mass being about 0.2 kg. The study emphasizes that the majority of bacterial cells reside in the colon, and the number of human cells is dominated by hematopoietic lineage cells. The researchers also note that the ratio of bacterial to human cells varies across different population segments, with a range from 1.3 to 2.3. The study highlights the importance of accurate estimates for understanding the role of the microbiota in human biology and underscores the need for further research to refine these estimates. The findings suggest that the human body contains roughly the same number of bacterial cells as human cells, with the bacterial mass accounting for about 0.3% of the body weight. The study also discusses the implications of these findings for understanding the human microbiome and its impact on health.