WT and [Delta]ompA E.coli compete in the same niche for colonization in the mouse intestine

Abstract

Escherichia coli is known to contain several outer membrane porin proteins that potentially play a role in its ability to colonize its host. One of the most abundant is the Beta barrel outer membrane protein A, or ompA. To study its role in colonization, an ompA-deletion mutant of commensal E.coli MG1655 was constructed. The [Delta]ompA strain was administered to mice in a series of experiments to determine how the absence of ompA would affect the colonization of E.coli in the mouse intestine. The [Delta]ompA mutant alone colonized in numbers equal to the wild type, supporting the idea that ompA is not vital to colonization. However, when WT and [Delta]ompA E.coli strains were administered simultaneously, WT outcompeted the [Delta]ompA by almost 4 log fold within 15 days of competition. To determine if the ompA mutant competes in the same niche as the WT, mice were associated with WT and then challenged with the ompA mutant. A second experiment was also done in reverse order. When WT was administered first followed by ompA, ompA was unable to colonize. Likewise, when ompA was administered first followed by WT, WT was unable to colonize. The results demonstrated that both strains compete in the same niche and once the niche is fully occupied by one strain, the other cannot colonize.