Mutations in enterobacterial common antigen biosynthesis restore outer membrane barrier function in Escherichia coli tol-pal mutants

The outer membrane (OM) is an essential component of the Gram-negative bacterial envelope that protects cells against external threats. To maintain a functional OM, cells require distinct mechanisms to ensure balance of proteins and lipids in the membrane. Mutations in OM biogenesis and/or homeostas...

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Bibliographic Details
Published inbioRxiv
Main Authors Jiang, Xiang'er, Tan, Wee Boon, Shrivastava, Rahul, Deborah Chwee San Seow, Swaine, Chen, Xue Li Guan, Shu-Sin Chng
Format Paper
LanguageEnglish
Published Cold Spring Harbor Cold Spring Harbor Laboratory Press 12.08.2020
Subjects
Antibiotics
Antigens
Diglycerides
E coli
Escherichia coli
Gram-negative bacteria
Homeostasis
Intermediates
Lipids
Mutation
Phospholipids
Recovery of function
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Summary:The outer membrane (OM) is an essential component of the Gram-negative bacterial envelope that protects cells against external threats. To maintain a functional OM, cells require distinct mechanisms to ensure balance of proteins and lipids in the membrane. Mutations in OM biogenesis and/or homeostasis pathways often result in permeability defects, but how molecular changes in the OM affect barrier function is unclear. Here, we seek potential mechanism(s) that can alleviate permeability defects in Escherichia coli cells lacking the Tol-Pal complex, which accumulate excess PLs in the OM. We identify mutations in enterobacterial common antigen (ECA) biosynthesis that re-establish OM barrier function against large hydrophilic molecules, yet did not restore lipid homeostasis. Furthermore, we demonstrate that build-up of biosynthetic intermediates, but not loss of ECA itself, contributes to the rescue. This suppression of OM phenotypes is unrelated to known effects that accumulation of ECA intermediates have on the cell wall. Finally, we reveal that an unusual diacylglycerol pyrophosphoryl-linked lipid species also accumulates in ECA mutants, and might play a role in the rescue phenotype. Our work provides insights into how OM barrier function can be restored independent of lipid homeostasis, and highlights previously unappreciated effects of ECA-related species in OM biology. Competing Interest Statement The authors have declared no competing interest.
DOI:10.1101/480533