BioProject

Colibactin, a bacterial genotoxin produced by E. coli harboring the pks genomic island, induces cytopathic effects such as DNA breaks, cell cycle arrest and apoptosis. More...

Colibactin, a bacterial genotoxin produced by E. coli harboring the pks genomic island, induces cytopathic effects such as DNA breaks, cell cycle arrest and apoptosis. Patients with a colonic dysfunction due to inflammatory bowel disease such as ulcerative colitis have an elevated likelihood of carrying pks+ E. coli in their colon microbiota but it is not clear whether and how they contribute to the pathogenesis of colitis. Using a gnotobiotic mouse model, we show that pks+ E. coli do not affect colonic integrity under homeostatic conditions, with the microbiota remaining separated from the epithelium by a mucus barrier. However, upon chemical disruption of this barrier by DSS, the microbes gain direct access to the epithelium, causing severe epithelial injury, and development of colitis, while mice colonized with an isogenic ΔclbR mutant incapable of producing colibactin suffer significantly less pronounced effects. While ΔclbR-colonized animals show efficient recovery of the mucus barrier and crypt homeostasis, recovery in WT-colonized mice is impaired. Instead, the mucosa remains in a chronic regenerative state characterized by high proliferation and impaired differentiation of enterocytes and goblet cells, preventing the re-establishment of a functional barrier. In turn, pks+ E. coli remain in direct contact with the epithelium, perpetuating the process and triggering chronic mucosal inflammation that morphologically and transcriptionally resembles human ulcerative colitis. It is characterized by high levels of stromal R-spondin 3. Genetic overexpression of R-spondin 3 in colon myofibroblasts is sufficient to mimic this chronic regenerative state, resulting in barrier disruption and expansion of E. coli. Together, our data reveal that pks+ E. coli are pathobionts that upon contact with the epithelium promote severe injury and interfere with recovery, initiating chronic tissue dysfunction and inflammation. Overall design: To study how colibactin-producing E. coli affect the colon epithelium, gnotobiotic E. coli-free mice, originally colonized by the Charles River altered Schaedler flora (CRASF®) were used, kindly provided by Till Strowig. These mice were used to establish in-house colonies of Enterobacteriaceae free C57BL/6, Axin2CreErt2/Rosa26-tdTomato and Krt20CreErt2/Rosa26-tdTomato mice Mice were treated for 48 h with 2 mg/ml streptomycin in drinking water. Streptomycin was replaced by drinking water 24 h before infection. Mice were infected with 1x 109 CFU of M1/5 E. coli, a pks+ E.coli strain and its isogenic Δ clbR mutant via oral gavage. At 5 days post-infection, mice were treated with 2% (Axin2CreErt2/Rosa26-tdTomato and Krt20CreErt2/Rosa26-tdTomato mice) or 2.5% DSS (C57BL/6) provided as drinking water for 7 days. After DSS treatment, mice were changed to normal drinking water and allowed to recover. Microarray experiments were performed as independent dual-color dye-reversal color-swap hybridizations using two biological replicates per group for the infected mice. on Agilent whole mouse catalog 4x44K (Agilent-014868) arrays. To compensate for dye-specific effects, a dye-reversal color-swap was applied. Less...