Periplasmic protein EipA determines envelope stress resistance and virulence inBrucella abortus
SummaryMolecular components of theBrucella abortuscell envelope play a major role in its ability to infect, colonize and survive inside mammalian host cells. In this study, we have defined a role for a conserved gene of unknown function inB. abortusenvelope stress resistance and infection. Expression of this gene, which we nameeipA,is directly activated by the essential cell cycle regulator, CtrA.eipAencodes a soluble periplasmic protein that adopts an unusual eight-stranded β-barrel fold. Deletion ofeipAattenuates replication and survival in macrophage and mouse infection models, and results in sensitivity to treatments that compromise the integrity of the cell envelope. Transposon disruption of genes required for LPS O-polysaccharide biosynthesis is synthetically lethal witheipAdeletion. This genetic connection between O-polysaccharide andeipAis corroborated by our discovery thateipAis essential inBrucella ovis, a naturally rough species that harbors mutations in several genes required for O-polysaccharide production. Conditional depletion ofeipAexpression inB. ovisresults in a cell chaining phenotype, providing evidence thateipAdirectly or indirectly influences cell division inBrucella. We conclude that EipA is a molecular determinant ofBrucellavirulence that functions to maintain cell envelope integrity and influences cell division.