Fig. 4
Bacterial strain dominance determines inflammatory and tumor responses. a Early evaluation of strain dominance. Viable CFU percentages of 9343 or 86 detected in stools harvested 1 week p.i. in SPF WT mice. Isolated B. fragilis colonies (up to 30) cultured from stool homogenates were randomly selected and screened by strain-specific PCR. In 11 of 12 9343→86 mice, only 9343 was detected (92%); in 1 of 12, both 9343 and 86 were detected in equal parts (8%). In 10 of 10 9343+86 mice, only 86 was detected (100%). b–e Relative strain quantification (B. fragilis copies/100 ng of DNA) by fecal qPCR at 2 weeks (SPF WT) or 12–16 weeks (SPF Min) and presented in the order of 9343(NT)/86(ET): lo/hi, hi/hi, or hi/lo. Low (lo) = 101 < 105 copies. High (hi) = ≥ 105 copies. Circles represent individual mice; triangles represent median Il17a expression or tumor counts (see right vertical axis). *Mice with hi/hi co-colonization levels. b Strain quantification in WT co-infected mice. c Strain quantification in Min co-infected mice. d Correlation of Il17a expression with 86 copies in WT mice. e Correlation of tumor number with 86 copies in Min mice. f Representative IF staining in SPF mice (2 to 4 weeks p.i.); images taken at ×400. Insets show images taken at ×630. The stippled line indicates the border between the luminal contents and the epithelial mucus layer. Panel 1: a WT Sham mouse; panel 2: a WT 9343-colonized mouse; panel 3: a WT 86-colonized mouse; panel 4: a Min 9343→86 co-colonized mouse. Strains 9343 and 86 colonize both the lumen and the mucosal surface with patchy mucus penetration (examples are shown with arrows) whether colonizing alone or in combination with another strain in the gut
