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

      1 , 2 , * , 1 , *

      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

                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
                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

                Article
                PBIOLOGY-D-16-00889
                10.1371/journal.pbio.1002533
                4991899
                27541692
                © 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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