A single rare σ70 variant establishes a unique gene expression pattern in the E. coli pathobiont LF82.

LF82, an adherent-invasive Escherichia coli (AIEC) pathobiont, is associated with Crohn's disease, an inflammatory bowel disease of unknown etiology. Although AIEC phenotypes differ from those of 'commensal' or pathogenic E. coli, work has failed to identify genetic features accounting for these differences.

The pathobiont LF82 encodes a unique variant of σ that results in specific gene expression changes and altered phenotypes.

LF82, an adherent invasive pathobiont, is associated with ileal Crohn's disease, an inflammatory bowel disease of unknown etiology. Although LF82 contains no virulence genes, it carries several genetic differences, including single nucleotide polymorphisms (SNPs), that distinguish it from nonpathogenic . We have identified and investigated an extremely rare SNP that is within the highly conserved gene, encoding σ, the primary sigma factor for RNA polymerase.