Comparing wild type Salmonella Typhimurium to a corA mutant

CorA is the primary Mg2+ channel in Salmonella enterica serovar Typhimurium. A strain lacking corA is attenuated in mice after infection either by oral gavage or intraperitoneal injection. Microarray studies show that several virulence effectors in Salmonella pathogenicity island 1 and Salmonella pathogenicity island 2 are repressed in the corA strain compared to wild type. While these results could be sufficient to explain the virulence deficit, the microarray data suggest additional defects that could also contribute. Motility is significantly reduced in a corA strain whereas enterochelin-dependent iron uptake and curli are upregulated. A corA strain is defective for invasion of and replication within Caco-2 epithelial cells. However, a corA strain does not have a significant survival defect in J774A.1 macrophages. Thus, despite the presence of two other Mg2+ transporters, loss of CorA affects multiple systems which manifests ultimately as a decrease in virulence. Keywords: strain comparison Cells were collected for RNA isolation on three separate days from wild type or corA strains giving six total samples from three independent cultures for each strain. A single microarray was run for each sample, three for wild type and three for the corA strain. Genomic DNA from wild type was used as a reference on each slide. Each microarray consists 3 subarrays.