Responder: "Viruses and Us"

This post is in response to Nicholas's first readers post "Viruses and Us". Nicholas mentioned the relationship of gut flora and human health in his post and I thought I would explore it a little further. Virtually all multicellular organisms live in close association with surrounding microbes, and humans are no exception. The human body is inhabited by a vast number of bacteria, archaea, viruses, and unicellular eukaryotes. The collection of microorganisms that live in peaceful coexistence with their hosts has been referred to as the microbiota, microflora, or normal flora (Kunz et al, 2009). The composition and roles of the bacteria that are part of this community have been intensely studied in the past few years. However, the roles of viruses, archaea, and unicellular eukaryotes that inhabit the mammalian body are less well known. It is estimated that the human microbiota contains as many as 10¹⁴ bacterial cells, a number that is 10 times greater than the number of human cells present in our bodies (Kunz et al, 2009). The microbiota colonizes virtually every surface of the human body that is exposed to the external environment. Microbes flourish on our skin and in the genitourinary, gastrointestinal, and respiratory tracts (Neish, 2009). By far the most heavily colonized organ is the gastrointestinal tract (GIT); the colon alone is estimated to contain over 70% of all the microbes in the human body (Neish, 2009). The human gut has an estimated surface area of a tennis court (200 m²) and, as such a large organ, represents a major surface for microbial colonization. Additionally, the GIT is rich in molecules that can be used as nutrients by microbes, making it a preferred site for colonization (Neish, 2009).

·      Kunz C, Kuntz S, Rudloff, S. “Intestinal flora”. Adv Exp Med Biol 639:67–79, 2009.

·      Neish, AS “Microbes in gastrointestinal health and disease”. Gastroenterology 136: 65–80, 2009.