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Life 2015, 5(2), 1333-1345;

Archaeal Lineages within the Human Microbiome: Absent, Rare or Elusive?

Division of Virology, Institute of Medical Microbiology, RWTH Aachen University Hospital, Pauwelsstrasse 30, 52057 Aachen, Germany
Academic Editors: Hans-Peter Klenk, Michael W. W. Adams and Roger A. Garrett
Received: 13 March 2015 / Revised: 27 April 2015 / Accepted: 28 April 2015 / Published: 5 May 2015
(This article belongs to the Special Issue Archaea: Evolution, Physiology, and Molecular Biology)
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Archaea are well-recognized components of the human microbiome. However, they appear to be drastically underrepresented compared to the high diversity of bacterial taxa which can be found on various human anatomic sites, such as the gastrointestinal environment, the oral cavity and the skin. As our “microbial” view of the human body, including the methodological concepts used to describe them, has been traditionally biased on bacteria, the question arises whether our current knowledge reflects the actual ratio of archaea versus bacteria or whether we have failed so far to unravel the full diversity of human-associated archaea. This review article hypothesizes that distinct archaeal lineages within humans exist, which still await our detection. First, previously unrecognized taxa might be quite common but they have eluded conventional detection methods. Two recent prime examples are described that demonstrate that this might be the case for specific archaeal lineages. Second, some archaeal taxa might be overlooked because they are rare and/or in low abundance. Evidence for this exists for a broad range of phylogenetic lineages, however we currently do not know whether these sporadically appearing organisms are mere transients or important members of the so called “rare biosphere” with probably basic ecosystem functions. Lastly, evidence exists that different human populations harbor different archaeal taxa and/or the abundance and activity of shared archaeal taxa may differ and thus their impact on the overall microbiome. This research line is rather unexplored and warrants further investigation. While not recapitulating exhaustively all studies on archaeal diversity in humans, this review highlights pertinent recent findings that show that the choice of appropriate methodological approaches and the consideration of different human populations may lead to the detection of archaeal lineages previously not associated with humans. This in turn will help understand variations found in the overall microbiomes from different individuals and ultimately may lead to the emergence of novel concepts/mechanisms impacting human health. View Full-Text
Keywords: human-associated archaea; human microbiome; periodontal disease; intestinal disorders; rare biosphere; anthropology of microbes human-associated archaea; human microbiome; periodontal disease; intestinal disorders; rare biosphere; anthropology of microbes
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Horz, H.-P. Archaeal Lineages within the Human Microbiome: Absent, Rare or Elusive? Life 2015, 5, 1333-1345.

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