The CorA Mg2+ channel is required for the virulence of Salmonella enterica serovar typhimurium

Abstract

CorA is the primary Mg(2+) channel in Salmonella enterica serovar Typhimurium. A corA mutant is attenuated in mice and defective for invasion of and replication within epithelial cells. Microarray studies show that several virulence effectors are repressed in a corA mutant strain, which ultimately manifests itself as a decrease in virulence.

FIG. 1.

Attenuation of a corA mutant strain after oral administration to BALB/c mice. Mice were infected by oral gavage with either the wild type (MM2089) at doses of 7 × 10⁹ (□) and 7 × 10⁸ (▪) cells, a corA mutant strain (MM2242) at doses of 5 × 10⁹ (○) and 5 ×10⁸ (•) cells, or a corA mutant strain with pCorA (MM2320) at a dose of 7 × 10⁸ cells (▴) as described in the text.

FIG. 2.

(A) Western blot assays of SPI-1 proteins were performed with total protein from the wild type (MM2089) and a corA mutant strain (MM2242) after growth in LB medium to log phase. The Western blot assays are representative of four independent experiments. Two independent experiments are shown. (B) The wild-type (MM2089) (top) and corA mutant (MM2242) (bottom) strains were plated at the centers of swim agar plates and allowed to grow at room temperature for 20 h. The data are representative of three independent experiments. WT, wild type.

FIG. 3.

(A) Epithelial cell invasion and survival by the wild-type strain (MM2089), a corA mutant strain (MM2242), a corA mutant strain with pCorA (MM2320), and a invA mutant strain (MM1364). Shown are data obtained 6 h after initiation of invasion. Similar results were obtained at other time points. The data are averages of three independent experiments. P values indicate t tests comparing the wild type to the other strains. (B) Time course of survival within J774.1 macrophages by the wild type (MM2089), a corA mutant strain (MM2242), a corA mutant strain with pCorA (MM2320), and a phoP mutant strain (MM3220). The data are from a single experiment representative of three independent experiments. WT, wild type.