The @entity526 species is divided in phylogenetic groups that differ in their virulence and commensal distribution. Strains belonging to the B2 group are involved in extra-intestinal pathologies but also appear to be more prevalent as commensals among @entity1 occidental populations. To investigate the genetic specificities of B2 sub-group, we used 128 sequenced genomes and identified genes of the core genome that showed marked difference between B2 and non-B2 genomes. We focused on the gene and its surrounding region with the strongest divergence between B2 and non-B2, the antiporter gene nhaA. This gene is part of the nhaAR operon, which is in the core genome but flanked by mobile regions, and is involved in growth at high pH and high @entity1372 concentrations. Consistently, we found that a panel of non-B2 strains grew faster than B2 at high pH and high @entity1372 concentrations. However, we could not identify differences in expression of the nhaAR operon using fluorescence reporter plasmids. Furthermore, the operon deletion had no differential impact between B2 and non-B2 strains, and did not result in a fitness modification in a @entity19 model of gut colonization. Nevertheless, sequence analysis and experiments in a @entity19 model of @entity295 revealed that recombination in nhaA among B2 strains was observed in strains with low virulence. Finally, nhaA and nhaAR operon deletions drastically decreased virulence in one B2 strain. This effect of nhaAR deletion appeared to be stronger than deletion of all pathogenicity islands. Thus, a population genetic approach allowed us to identify an operon in the core genome without strong effect in commensalism but with an important role in extra-intestinal virulence, a landmark of the B2 strains.

The conserved nhaAR operon is drastically divergent between B2 and non-B2 XXXX and is involved in extra-intestinal virulence.

@entity1 :: ('9606', 'Species') :: ['human'] @entity295 :: ('MESH:D018805', 'Disease') :: ['septicemia'] @entity19 :: ('10090', 'Species') :: ['murine'] @entity1372 :: ('MESH:D012964', 'Chemical') :: ['sodium'] @entity526 :: ('562', 'Species') :: ['Escherichia coli']
@entity526 :: (562,Species) :: ['Escherichia coli']
