Polar localization of putative phospholipid transporters in Escherichia coli

The Gram-negative bacterial cell envelope comprises an outer membrane (OM) with an asymmetric arrangement of lipopolysaccharides (LPS) and phospholipids (PLs), protecting them from both physical and chemical threats. To build the OM, PLs must be transported across the cell envelope; this process has remained elusive until recently, where three collectively essential AsmA-superfamily proteins – YhdP, TamB, and YdbH – are proposed to function as anterograde PL transporters in Escherichia coli . Here, we discover that all three proteins are strongly enriched at the cell poles. We also identify a novel interacting partner of YhdP, which provides possible insights into its localization mechanism. Our observation raises the possibility that anterograde PL transport could be spatially restricted to the cell poles, and highlights the importance of understanding the spatial-temporal regulation of OM biogenesis in coordination with cell growth and division.