Com que els bacteris són de 10 a 100 vegades més petits que les cèl·lules humanes, la microbiota sencera pesa uns 200 grams. Vegeu també Coyle, MD, Walter J. «The Human Microbiome: The Undiscovered Country» p. 16. [Consulta: 2 març 2012].
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Qin J, Li R, Raes J, Arumugam M, Burgdorf KS, Manichanh C, Nielsen T, Pons N, Levenez F, Yamada T, Mende DR, Li J, Xu J, Li S, Li D, Cao J, Wang B, Liang H, Zheng H, Xie Y, Tap J, Lepage P, Bertalan M, Batto JM, Hansen T, Le Paslier D, Linneberg A, Nielsen HB, Pelletier E, Renault P, Sicheritz-Ponten T, Turner K, Zhu H, Yu C, Li S, Jian M, Zhou Y, Li Y, Zhang X, Li S, Qin N, Yang H, Wang J, Brunak S, Doré J, Guarner F, Kristiansen K, Pedersen O, Parkhill J, Weissenbach J; MetaHIT Consortium, Bork P, Ehrlich SD, Wang J. «A human gut microbial gene catalogue established by metagenomic sequencing». Nature, Vol. 464, 7285, 2009, pàg. 59-65. DOI: 10.1038/nature08821. PMC: 3779803. PMID: 20203603.
NIH HMP Working Group, Peterson J, Garges S, Giovanni M, McInnes P, Wang L, Schloss JA, Bonazzi V, McEwen JE, Wetterstrand KA, Deal C, Baker CC, Di Francesco V, Howcroft TK, Karp RW, Lunsford RD, Wellington CR, Belachew T, Wright M, Giblin C, David H, Mills M, Salomon R, Mullins C, Akolkar B, Begg L, Davis C, Grandison L, Humble M, Khalsa J, Little AR, Peavy H, Pontzer C, Portnoy M, Sayre MH, Starke-Reed P, Zakhari S, Read J, Watson B, Guyer M «The NIH Human Microbiome Project.». Genome Res, Vol. 19, num. 12, 2009, pàg. 2317-23. DOI: 10.1101/gr.096651.109. PMC: 2792171. PMID: 19819907.
Qin J, Li R, Raes J, Arumugam M, Burgdorf KS, Manichanh C, Nielsen T, Pons N, Levenez F, Yamada T, Mende DR, Li J, Xu J, Li S, Li D, Cao J, Wang B, Liang H, Zheng H, Xie Y, Tap J, Lepage P, Bertalan M, Batto JM, Hansen T, Le Paslier D, Linneberg A, Nielsen HB, Pelletier E, Renault P, Sicheritz-Ponten T, Turner K, Zhu H, Yu C, Li S, Jian M, Zhou Y, Li Y, Zhang X, Li S, Qin N, Yang H, Wang J, Brunak S, Doré J, Guarner F, Kristiansen K, Pedersen O, Parkhill J, Weissenbach J; MetaHIT Consortium, Bork P, Ehrlich SD, Wang J. «A human gut microbial gene catalogue established by metagenomic sequencing». Nature, Vol. 464, 7285, 2009, pàg. 59-65. DOI: 10.1038/nature08821. PMC: 3779803. PMID: 20203603.
Zimmer, Carl «Bacteria Divide People Into 3 Types, Scientists Say». The New York Times, 20-04-2011 [Consulta: 21 abril 2011]. «a group of scientists now report just three distinct ecosystems in the guts of people they have studied.»