Humanized mouse gut microbiota transplant experiments. A: Design of experiments in which initial human fecal samples colonize mouse gut, adapt to various diets (low fat/plant polysaccharide (LF/PP) diet or Western diet), and are evaluated. Brown arrows indicate fecal collection time points (Generation 1). B: Reciprocal microbiota transplants in which microbiota from first-generation (A) humanized mice fed Western or LF/PP diet were transferred to LF/PP or Western-fed germ-free recipients. C: Taxonomic distribution of the bacteria in the two generation experiments described in A/B. Values represent the average relative abundance across all samples within the indicated groups following analysis of 16S rRNA gene surveys. Reproduced with permission (Turnbaugh PJ, et al. Sci Transl Med 2009;1:6ra14).¹⁵