The gut microbiota strongly impacts the development of sporadic colorectal cancer (CRC), but it is largely unknown how the microbiota affects the pathogenesis of mismatch-repair-deficient CRC in... Show moreThe gut microbiota strongly impacts the development of sporadic colorectal cancer (CRC), but it is largely unknown how the microbiota affects the pathogenesis of mismatch-repair-deficient CRC in the context of Lynch syndrome. In a mouse model for Lynch syndrome, we found a nearly complete loss of intestinal tumor development when animals were transferred from a conventional "open" animal facility to specific-pathogen-free (SPF) conditions. Using 16S sequencing we detected large changes in microbiota composition between the two facilities. Transcriptomic analyses of tumor-free intestinal tissues showed signs of strong intestinal inflammation in conventional mice. Whole exome sequencing of tumors developing in Msh2-Lynch mice revealed a much lower mutational load in the single SPF tumor than in tumors developing in conventional mice, suggesting reduced epithelial proliferation in SPF mice. Fecal microbiota transplantations with conventional feces altered the immune landscape and gut homeostasis, illustrated by increased gut length and elevated epithelial proliferation and migration. This was associated with drastic changes in microbiota composition, in particular increased relative abundances of different mucus-degrading taxa such as Desulfovibrio and Akkermansia, and increased bacterial-epithelial contact. Strikingly, transplantation of conventional microbiota increased microsatellite instability in untransformed intestinal epithelium of Msh2-Lynch mice, indicating that the composition of the microbiota influences the rate of mutagenesis in MSH2-deficient crypts. Show less
Xiao, X.S.; Willemse, J.; Voskamp, P.; Li, X.M.; Prota, A.E.; Lamers, M.; ... ; Wezel, G.P. van 2021
In most bacteria, cell division begins with the polymerization of the GTPase FtsZ at mid-cell, which recruits the division machinery to initiate cell constriction. In the filamentous bacterium... Show moreIn most bacteria, cell division begins with the polymerization of the GTPase FtsZ at mid-cell, which recruits the division machinery to initiate cell constriction. In the filamentous bacterium Streptomyces, cell division is positively controlled by SsgB, which recruits FtsZ to the future septum sites and promotes Z-ring formation. Here, we show that various amino acid (aa) substitutions in the highly conserved SsgB protein result in ectopically placed septa that sever spores diagonally or along the long axis, perpendicular to the division plane. Fluorescence microscopy revealed that between 3.3% and 9.8% of the spores of strains expressing SsgB E120 variants were severed ectopically. Biochemical analysis of SsgB variant E120G revealed that its interaction with FtsZ had been maintained. The crystal structure of Streptomyces coelicolor SsgB was resolved and the key residues were mapped on the structure. Notably, residue substitutions (V115G, G118V, E120G) that are associated with septum misplacement localize in the alpha 2-alpha 3 loop region that links the final helix and the rest of the protein. Structural analyses and molecular simulation revealed that these residues are essential for maintaining the proper angle of helix alpha 3. Our data suggest that besides altering FtsZ, aa substitutions in the FtsZ-recruiting protein SsgB also lead to diagonally or longitudinally divided cells in Streptomyces. Show less
Jansen, J.G.; Tsaalbi-Shtylik, A.; Wind, N. de 2015
