| Comments |
p.5859 right column 3rd paragraph: "These observations support the notion that gut microbes may live at the intersection of 2 forms of selective pressure: bottom-up selection, where fierce competition between members of a community that approaches a population density of 10^11 to 10^12 organisms per milliliter of colonic contents drives phylotypes to assume distinct functional roles (niches): and top-down selection, where the host selects for functional redundancy to ensure against the failure of bioreactor functions that could prove highly deleterious (refs 9, 10)." |