Genetic interaction mapping highlights key roles of the Tol‐Pal complex. Issue 4 (21st February 2022)

• Record Type: Journal Article
• Authors: Tan, Wee Boon; Chng, Shu‐Sin
• Is Part Of: Molecular microbiology. Volume 117:Issue 4(2022)
• Page Start: 921
• Page End: 936
• Publication Date: 2022-02-21
• Subjects: Molecular microbiology -- Periodicals; 572.829
• DOI: 10.1111/mmi.14882
• Languages: English
• ISSNs: 0950-382X

Abstract

Abstract: The conserved Tol‐Pal trans‐envelope complex is important for outer membrane (OM) stability and cell division in Gram‐negative bacteria. It is proposed to mediate OM constriction during cell division via cell wall tethering. Yet, recent studies suggest the complex has additional roles in OM lipid homeostasis and septal wall separation. How Tol‐Pal facilitates all these processes is unclear. To gain insights into its function(s), we applied transposon‐insertion sequencing, and report here a detailed network of genetic interactions with the tol‐pal locus in Escherichia coli . We found one positive and > 20 negative strong interactions based on fitness. Disrupting osmoregulated‐periplasmic glucan biosynthesis restores fitness and OM barrier function, but not proper division, in tol‐pal mutants. In contrast, deleting genes involved in OM homeostasis and cell wall remodeling causes synthetic growth defects in strains lacking Tol‐Pal, especially exacerbating OM barrier and/or division phenotypes. Notably, the Δ tolA mutant having additional defects in OM protein assembly (Δ bamB ) exhibited severe division phenotypes, even when single mutants divided normally; this highlights the possibility for OM phenotypes to indirectly impact cell division. Overall, our work underscores the intricate nature of Tol‐Pal function, and reinforces its key roles in cell wall‐OM tethering, cell wall remodeling, and in particular, OM homeostasis. Abstract : The Tol‐Pal trans‐envelope complex plays important, multi‐faceted roles in Gram‐negative bacterial cell envelope biogenesis. We compared saturated transposon insertion profiles in Escherichia coli Δ tolQ and Δ tolA backgrounds with the wild type to map genome‐wide genetic interactions with the tol‐pal locus. In addition to its role in outer membrane‐cell wall tethering, our results highlight critical requirements for Tol‐Pal in maintaining proper cell wall remodeling and outer membrane homeostasis.