Outer membrane lipoprotein DolP interacts with the BAM complex and promotes fitness during envelope stress response

In Gram-negative bacteria, coordinated remodelling of the outer membrane (OM) and the peptidoglycan is crucial for envelope integrity. Envelope stress caused by unfolded OM proteins (OMPs) activates sigmaE(σE) in Enterobacteria. Whereas σE upregulates biogenesis factors, including the β-barrel assembly machinery (BAM) that catalyzes OMP-folding, elevated σE activity can be detrimental for OM integrity. We report that DolP (YraP), a σE-upregulated OM lipoprotein needed for envelope integrity, is a novel interactor of BAM and that BamA is a critical determinant of the BAM-DolP complex. Mid-cell recruitment of DolP had been reported to promote septal peptidoglycan remodelling during cell division, but the role of DolP during envelope stress was unknown. Using a synthetic-defect CRISPRi screen, we found that dolP is critical in cells with elevated or constitutive σE activation. Differently from other σE-upregulated proteins, DolP is not directly implicated in OMP assembly. Envelope stress or OM-overaccumulating BamA, however, interferes with DolP septal recruitment. Taken together, our results uncover DolP as a fitness factor during σE activation, and support a model where differential septal recruitment of DolP contributes to link envelope stress to a late step of cell division.