Peptidoglycan maturation controls spatiotemporal organisation of outer membrane proteins in Escherichia coli

Abstract

Linkages between the outer membrane of Gram-negative bacteria and the peptidoglycan layer are crucial to the maintenance of cellular integrity and enable survival in challenging environments. The functionality of the outer membrane relies on outer membrane proteins (OMPs), which are inserted by the β-barrel assembly machine, BAM. Previous work has shown that growing Escherichia coli cells segregate old OMPs towards the poles by an unknown mechanism. Here, we demonstrate that peptidoglycan underpins the spatiotemporal organisation of OMPs. Mature, tetrapeptide-rich peptidoglycan binds to BAM components and suppresses OMP foldase activity. Nascent peptidoglycan, which is enriched in pentapeptides and concentrated at septa, associates with BAM poorly and has little impact on its activity, leading to preferential insertion of OMPs at division sites. Synchronising OMP biogenesis to cell wall growth enables bacteria to replenish their OMPs by binary partitioning. Our study reveals that Gram-negative bacteria coordinate the assembly of two major cell envelope layers by rendering OMP biogenesis responsive to peptidoglycan maturation. This coordination offers new possibilities for the design of antibiotics that disrupt cell envelope integrity.

Non-typeable Haemophilus influenzae major outer membrane protein P5 contributes to bacterial membrane stability, and affects the membrane protein composition crucial for interactions with the human host

“…Based on the ranking of relative abundance, virulence factors such as major adhesins (i.e., High molecular weight adhesin (HMW) and Haemophilus adhesin protein (Hap)) and IgA protease were less represented while P2, PD, PF and PE were more abundant in the P5-knockout mutant, with respect to the wild-type strain (Table S3) (Duell et al, 2016). We also noticed that periplasmic chaperones (SurA, Omp26 and DegP) and Bam complex subunit proteins (BamA, C, D and E) that are essential for proper folding and assembly of OM proteins, respectively, were less abundant in the mutant (Knowles et al, 2009;Calmettes et al, 2015;Mamou et al, 2022).…”

“…The OmpA-like domain serves as an anchor between the OM layer and the peptidoglycan. The interaction is crucial for OM-cell wall stability, and the assembly of membrane and cell wall proteins (Hancock et al, 1994;Knowles et al, 2009;Park et al, 2012;Calmettes et al, 2015;Ortiz-Suarez et al, 2016;Samsudin et al, 2016;Graham et al, 2021;Mamou et al, 2022). Since we showed that P5 CTD of NTHi 3655 has peptidoglycan-binding activity, we hypothesized a possible role for P5 in the distribution of NTHi periplasmic and membrane protein (membrane proteome).…”