Colonization resistance against genetically modified Escherichia coli K12 (W3110) strains is abrogated following broad-spectrum antibiotic treatment and acute ileitis

Survival of Escherichia coli harboring nucleic acid-hydrolyzing 3D8 scFv during RNA virus infection

Previously, Escherichia coli harboring the codon-optimized 3D8scFv gene (E. coli 3D8scFv) was developed as a feed additive for use in preventing norovirus infection. Here, we evaluated whether the 3D8scFv gene affects the colonization of E coli when E. coli 3D8scFv passes through the mouse gastrointestinal tract. To determine the colonization ability of E. coli 3D8scFv, E. coli cells with or without the 3D8scFv gene were fed to mice. Total DNA was extracted from the animals’ stools, stomach, small intestine and colon. All samples were amplified using 3D8scFv gene-specific primer sets. E. coli 3D8scFv begins to be excreted 1 h after feeding and that all E. coli 3D8scFv cells were excreted between 12 and 24 h after the last feeding of the cells. The previously measured gastrointestinal transit time of the mice was between 8 h and 22 h. The results of this study therefore show that E. coli 3D8scFv cannot colonize the gastrointestinal tracts of mice. In addition, if the purified 3D8 scFv protein is used as a feed additive, any associated E. coli 3D8scFv bacteria will not colonize the gastrointestinal tracts of the livestock. Thus, this feed additive meets the safety assessment criteria for the commercial use of bacteria.

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It is evaluated whether E. coli 3D8scFv colonizes in the gastrointestinal tracts of mice.

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Orally ingested E. coli 3D8scFv is excreted from mice without colonization of the gastrointestinal tract.

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Purified 3D8 scFv is suitable for a feed additive according to the concept of substantial equivalence.

Interplay between enterobactin, myeloperoxidase and lipocalin 2 regulates E. coli survival in the inflamed gut

During an inflammatory response in the gut, some commensal bacteria such as E. coli can thrive and contribute to disease. Here we demonstrate that enterobactin (Ent), a catecholate siderophore released by E. coli, is a potent inhibitor of myeloperoxidase (MPO), a bactericidal enzyme of the host. Glycosylated Ent (salmochelin) and non-catecholate siderophores (yersiniabactin and ferrichrome) fail to inhibit MPO activity. An E. coli mutant (ΔfepA) that overproduces Ent, but not an Ent-deficient double mutant (ΔaroB/ΔfepA), inhibits MPO activity and exhibits enhanced survival in inflamed guts. This survival advantage is counter-regulated by lipocalin 2, a siderophore-binding host protein, which rescues MPO from Ent-mediated inhibition. Spectral analysis reveals that Ent interferes with compound I [oxoiron, Fe(IV)=O] and reverts the enzyme back to its native ferric [Fe(III)] state. These findings define a fundamental mechanism by which E. coli surpasses the host innate immune responses during inflammatory gut diseases and gains a distinct survival advantage.

Impact of metal ion homeostasis of genetically modified Escherichia coli Nissle 1917 and K12 (W3110) strains on colonization properties in the murine intestinal tract

Metal ions are integral parts of pro- as well as eukaryotic cell homeostasis. Escherichia coli proved a valuable in vitro model organism to elucidate essential mechanisms involved in uptake, storage, and export of metal ions. Given that E. coli Nissle 1917 is able to overcome murine colonization resistance, we generated several E. coli Nissle 1917 mutants with defects in zinc, iron, copper, nickel, manganese homeostasis and performed a comprehensive survey of the impact of metal ion transport and homeostasis for E. coli colonization capacities within the murine intestinal tract. Seven days following peroral infection of conventional mice with E. coli Nissle 1917 strains exhibiting defined defects in zinc or iron uptake, the respective mutant and parental strains could be cultured at comparable, but low levels from the colonic lumen. We next reassociated gnotobiotic mice in which the microbiota responsible for colonization resistance was abrogated by broad-spectrum antibiotics with six different E. coli K12 (W3110) mutants. Seven days following peroral challenge, each mutant and parental strain stably colonized duodenum, ileum, and colon at comparable levels. Taken together, defects in zinc, iron, copper, nickel, and manganese homeostasis do not compromise colonization capacities of E. coli in the murine intestinal tract.