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

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PLoS Biology

Public Library of Science

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      Abstract

      Reported values in the literature on the number of cells in the body differ by orders of magnitude and are very seldom supported by any measurements or calculations. Here, we integrate the most up-to-date information on the number of human and bacterial cells in the body. We estimate the total number of bacteria in the 70 kg "reference man" to be 3.8·10 13. For human cells, we identify the dominant role of the hematopoietic lineage to the total count (≈90%) and revise past estimates to 3.0·10 13 human cells. Our analysis also updates the widely-cited 10:1 ratio, showing that the number of bacteria in the body is actually of the same order as the number of human cells, and their total mass is about 0.2 kg.

      Abstract

      Thoroughly revised estimates show that the typical adult human body consists of about 30 trillion human cells and about 38 trillion bacteria.

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      Most cited references 35

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      A human gut microbial gene catalogue established by metagenomic sequencing.

      To understand the impact of gut microbes on human health and well-being it is crucial to assess their genetic potential. Here we describe the Illumina-based metagenomic sequencing, assembly and characterization of 3.3 million non-redundant microbial genes, derived from 576.7 gigabases of sequence, from faecal samples of 124 European individuals. The gene set, approximately 150 times larger than the human gene complement, contains an overwhelming majority of the prevalent (more frequent) microbial genes of the cohort and probably includes a large proportion of the prevalent human intestinal microbial genes. The genes are largely shared among individuals of the cohort. Over 99% of the genes are bacterial, indicating that the entire cohort harbours between 1,000 and 1,150 prevalent bacterial species and each individual at least 160 such species, which are also largely shared. We define and describe the minimal gut metagenome and the minimal gut bacterial genome in terms of functions present in all individuals and most bacteria, respectively.
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        Human gut microbiome viewed across age and geography

        Gut microbial communities represent one source of human genetic and metabolic diversity. To examine how gut microbiomes differ between human populations when viewed from the perspective of component microbial lineages, encoded metabolic functions, stage of postnatal development, and environmental exposures, we characterized bacterial species present in fecal samples obtained from 531 individuals representing healthy Amerindians from the Amazonas of Venezuela, residents of rural Malawian communities, and inhabitants of USA metropolitan areas, as well as the gene content of 110 of their microbiomes. This cohort encompassed infants, children, teenagers and adults, parents and offspring, and included mono- and dizygotic twins. Shared features of the functional maturation of the gut microbiome were identified during the first three years of life in all three populations, including age-associated changes in the representation of genes involved in vitamin biosynthesis and metabolism. Pronounced differences in bacterial species assemblages and functional gene repertoires were noted between individuals residing in the USA compared to the other two countries. These distinctive features are evident in early infancy as well as adulthood. In addition, the similarity of fecal microbiomes among family members extends across cultures. These findings underscore the need to consider the microbiome when evaluating human development, nutritional needs, physiological variations, and the impact of Westernization.
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          Cancer etiology. Variation in cancer risk among tissues can be explained by the number of stem cell divisions.

          Some tissue types give rise to human cancers millions of times more often than other tissue types. Although this has been recognized for more than a century, it has never been explained. Here, we show that the lifetime risk of cancers of many different types is strongly correlated (0.81) with the total number of divisions of the normal self-renewing cells maintaining that tissue's homeostasis. These results suggest that only a third of the variation in cancer risk among tissues is attributable to environmental factors or inherited predispositions. The majority is due to "bad luck," that is, random mutations arising during DNA replication in normal, noncancerous stem cells. This is important not only for understanding the disease but also for designing strategies to limit the mortality it causes. Copyright © 2015, American Association for the Advancement of Science.
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            Author and article information

            Affiliations
            [1 ]Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel
            [2 ]Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
            Author notes

            The authors have declared that no competing interests exist.

            [¤]

            Current address: Division of Endocrinology, The Hospital for Sick Children and Department of Pediatrics, The University of Toronto, Toronto, Canada

            Journal
            PLoS Biol
            PLoS Biol
            plos
            plosbiol
            PLoS Biology
            Public Library of Science (San Francisco, CA USA )
            1544-9173
            1545-7885
            19 August 2016
            August 2016
            19 August 2016
            : 14
            : 8
            27541692 4991899 10.1371/journal.pbio.1002533 PBIOLOGY-D-16-00889
            © 2016 Sender et al

            This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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            Figures: 3, Tables: 3, Pages: 14
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            Funding
            This work was funded by the European Research Council (Project NOVCARBFIX 646827, https://erc.europa.eu/funding-and-grants); Dana and Yossie Hollander; Helmsley Charitable Foundation; The Larson Charitable Foundation; The Estate of David Arthur Barton; The Anthony Stalbow Charitable Trust, and Stella Gelerman, Canada. RM is the Charles and Louise Gartner professional chair and an EMBO young investigator program member. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
            Categories
            Essay
            Biology and Life Sciences
            Anatomy
            Digestive System
            Gastrointestinal Tract
            Colon
            Medicine and Health Sciences
            Anatomy
            Digestive System
            Gastrointestinal Tract
            Colon
            Biology and Life Sciences
            Organisms
            Bacteria
            Biology and Life Sciences
            Cell Biology
            Cellular Types
            Animal Cells
            Blood Cells
            Red Blood Cells
            People and Places
            Population Groupings
            Age Groups
            Adults
            Research and Analysis Methods
            Cell Enumeration Techniques
            Total Cell Counting
            Biology and Life Sciences
            Organisms
            Bacteria
            Gut Bacteria
            Biology and Life Sciences
            Cell Biology
            Cellular Types
            Animal Cells
            Connective Tissue Cells
            Fibroblasts
            Biology and Life Sciences
            Anatomy
            Biological Tissue
            Connective Tissue
            Connective Tissue Cells
            Fibroblasts
            Medicine and Health Sciences
            Anatomy
            Biological Tissue
            Connective Tissue
            Connective Tissue Cells
            Fibroblasts
            Biology and Life Sciences
            Physiology
            Physiological Parameters
            Body Weight
            Obesity
            Medicine and Health Sciences
            Physiology
            Physiological Parameters
            Body Weight
            Obesity

            Life sciences

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