Fig. 7: Neonatal mouse model small intestine competition assay.
From: Antibacterial microcins are ubiquitous and functionally diverse across bacterial communities
A Zone of inhibition (ZOI) assays for E. coli B41 Lac+ secreting a microcin (EN43, EN44, EN112) or negative control (NC) on E. coli W3110 or E. coli B41. Only EN43 and EN44 produced a ZOI on E. coli B41 and were selected for in vivo competition experiments. Images are representative of triplicate assays. B Neonatal mice are gavaged with E. coli B41 encoding secretion of a microcin/control (Lac+, blue) and a control (Lac-, white) at a 1:1 ratio. After transit to the small intestine, microcin expression is induced, and the small intestine is excised and plated to determine the ‘competitive index’: the normalized ratio of blue (secretor): white(control) colony-forming units (CFU). Created in BioRender. Parker, J. (2025) https://BioRender.com/2xrcyef. C Competitive index per mouse small intestine. Two experiments were performed with 5 mice each for EN43 and NC (n = 10 per microcin) and 4 mice each for EN44 (n = 8). The target pathogen was outcompeted by the EN43 and EN44 microcin secretors (p = 9.8 × 10−5, Kruskal-Wallis test; pEN43-NC = 0.00012 and pEN44-NC = 0.0045, Dunn’s test.
