Human microbiome

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Yersinia enterocolitica colonies growing on XLD agar plates
Staphylococcus aureus, magnified x50,000, image by transmission electron microscope
Escherichia coli: a long-term resident in our gut

The human microbiome (or human microbiota) is the collection of microorganisms which live on us. They live on the skin, in the saliva and mouth, in the eyes, and in the gut and the rest of the gastrointestinal tract. They include bacteria, archaea, fungi and single-celled eukaryotes ('protozoa').[1] Everyone carries around far more of these microbes than the number of human cells in the body. The human body has about 100 trillion cells, and carries about ten times as many microorganisms in the intestines alone.[2][3][4][5]

The microbiome is "the ecological community of commensal, symbiotic, and pathogenic microorganisms that literally share our body space".[6][7] The term was originally coined by Joshua Lederberg, who argued the importance of microorganisms inhabiting the human body in health and disease. Many scientific articles distinguish "microbiome" and "microbiota" to describe either the collective genomes of the microorganisms that reside in an environmental niche or the microorganisms themselves, respectively.[8][9][10] However, by the original definitions these terms are largely synonymous.

Some of these organisms are useful for humans. However, most have no known effect. They are just symbionts: they live with us. Those which are expected to be present are members of the normal flora. Under normal circumstances they do not cause disease, but may even help our health. Studies in 2009 asked whether our health is damaged if we reduce this biota.[11] This is certainly the case with gut flora.[3]

Although "flora" refers to plants rather than bacteria, the term 'gut flora' is widely used and familiar to biologists. 'Biota' refers to the total collection of organisms in an ecosystem. The term 'microbiota' is best for bacteria and other microorganisms, but no doubt 'flora' will often be used.

The microbes being discussed are generally non-pathogenic (do not cause disease unless they grow abnormally); they exist in harmony and symbiotically with their hosts.[12]

Researchers have learned that much of the population of microbes found in the human body are not bacteria but a very old class of single-celled organisms called archaea.[12] They include methanogens which produce methane and may cause flatulence.

Related pages[change | change source]

References[change | change source]

  1. Mundasad, Smitha 2012. Human Microbiome Project reveals largest microbial map. BBC News: Health [1]
  2. Björkstén B. et al (2001). "Allergy development and the intestinal microflora during the first year of life". J. Allergy Clin. Immunol. 108 (4): 516–20. doi:10.1067/mai.2001.118130 . PMID 11590374 .
  3. 3.0 3.1 Guarner F. & Malagelada J.R. (2003). "Gut flora in health and disease". Lancet 361 (9356): 512–9. doi:10.1016/S0140-6736(03)12489-0 . PMID 12583961 .
  4. Sears C.L. (2005). "A dynamic partnership: celebrating our gut flora". Anaerobe 11 (5): 247–51. doi:10.1016/j.anaerobe.2005.05.001 . PMID 16701579 .
  5. Steinhoff U (2005). "Who controls the crowd? New findings and old questions about the intestinal microflora". Immunol. Lett. 99 (1): 12–6. doi:10.1016/j.imlet.2004.12.013 . PMID 15894105 .
  6. Lederberg J. & McCray A.T. 2001. ’Ome Sweet ’Omics — a genealogical treasury of words. Scientist. [2]
  7. The NIH HMP Working Group. 2009. The NIH Human Microbiome Project. Genome Res. 19(12): 2317–2323. [3]
  8. Backhed, F. et al 2005. Host-bacterial mutualism in the human intestine. Science 307, 1915.
  9. Turnbaugh P.J. et al 2007. The Human Microbiome Project. Nature. 449:804-810. doi:10.1038/nature06244
  10. Ley R.E; Peterson D.A. & Gordon J.I. 2006. Ecological and evolutionary forces shaping microbial diversity in the human intestine. Cell. 124: 837-848. doi:10.1016/j.cell.2006.02.017
  11. Bugs inside: what happens when the microbes that keep us healthy disappear?, Katherine Harmon, Scientific American, December 2009, accessed 27 December 2009
  12. 12.0 12.1 Madigan, Michael T. (2012). Brock biology of microorganisms (13th ed.). San Francisco: Benjamin Cummings. ISBN 9780321649638 .