Journal
MOLECULAR MICROBIOLOGY
Volume 114, Issue 6, Pages 991-1005Publisher
WILEY
DOI: 10.1111/mmi.14590
Keywords
ECA; lipid homeostasis; MPIase; outer membrane barrier; Tol-Pal complex; vancomycin resistance
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Funding
- Genome Institute of Singapore
- Nanyang Technological University
- Ministry of Education - Singapore
- National Medical Research Council [NMRC/CBRG/0072/2014, NMRC/CIRG/1357/2013]
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The outer membrane (OM) is an essential component of the Gram-negative bacterial envelope that protects the 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 inEscherichia colicells 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.
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