Structural Variations in Ulcerative Colitis-associated Escherichia coli Reduce Fructose Utilization and Aggravate Inflammation Under High-Fructose Diet.

Background & Aims: Structural variations (SVs) have significant effects on microbial phenotypes. The underlying mechanism of functional changes caused by gut microbial SVs in the development of ulcerative colitis (UC) need further investigation.

Methods: We performed long-read (Oxford Nanopore Technology-based) and short-read (Illumina-based) metagenomic sequencing on stool samples from 93 patients with UC and 100 healthy controls (HCs) and analyzed microbial SVs. A total of 648 Escherichia coli (E coli) strains from fecal samples of patients with UC (UC-strains) and HCs (HC-strains) were isolated. SV-associated scrK gene deletion was verified via whole-genome sequencing or targeted polymerase chain reaction. Then, representative UC-strains, HC-strains, and scrK-knockout E coli were used for the in vitro and in vivo experiments to investigate the effects of specific SVs in E coli on fructose utilization ability and colitis.

Results: E coli in UC with the highest fold change had SV-affected functional differences on fructose metabolism to that of HCs. The fructose utilization gene deletion was common in UC-strains, ostensibly reducing fructose utilization in vitro and leading to fructose-dependent aggravation of colitis in murine models. UC-strains and HC-strains induced comparable colitis under low fructose. However, high fructose exacerbated colitis severity exclusively in UC-strain-colonized mice, with elevated intestinal fructose residues, significant microbiome/metabolome changes, increased inflammation, and gut barrier disruption. These changes were mechanistically dependent on the deletion of the fructose utilization gene scrK.

Conclusions: SV-caused difference in fructose utilization and proinflammatory properties in E coli from patients with UC influence the development of UC, emphasizing the importance of fine-scale metagenomic studies in disease.