Dissecting Escherichia coli outer membrane biogenesis using differential proteomics

PLoS One. 2014 Jun 26;9(6):e100941. doi: 10.1371/journal.pone.0100941. eCollection 2014.


The cell envelope of Gram-negative bacteria is a complex multi-layered structure comprising an inner cytoplasmic membrane and an additional asymmetric lipid bilayer, the outer membrane, which functions as a selective permeability barrier and is essential for viability. Lipopolysaccharide, an essential glycolipid located in the outer leaflet of the outer membrane, greatly contributes to the peculiar properties exhibited by the outer membrane. This complex molecule is transported to the cell surface by a molecular machine composed of seven essential proteins LptABCDEFG that form a transenvelope complex and function as a single device. While advances in understanding the mechanisms that govern the biogenesis of the cell envelope have been recently made, only few studies are available on how bacterial cells respond to severe envelope biogenesis defects on a global scale. Here we report the use of differential proteomics based on Multidimensional Protein Identification Technology (MudPIT) to investigate how Escherichia coli cells respond to a block of lipopolysaccharide transport to the outer membrane. We analysed the envelope proteome of a lptC conditional mutant grown under permissive and non permissive conditions and identified 123 proteins whose level is modulated upon LptC depletion. Most such proteins belong to pathways implicated in cell envelope biogenesis, peptidoglycan remodelling, cell division and protein folding. Overall these data contribute to our understanding on how E. coli cells respond to LPS transport defects to restore outer membrane functionality.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Outer Membrane Proteins / metabolism*
  • Biological Transport
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins / metabolism*
  • Lipopolysaccharides / chemistry
  • Lipopolysaccharides / metabolism
  • Membrane Proteins / metabolism
  • Protein Transport
  • Proteome*
  • Proteomics* / methods
  • Stress, Physiological


  • Bacterial Outer Membrane Proteins
  • Escherichia coli Proteins
  • Lipopolysaccharides
  • LptC protein, E coli
  • Membrane Proteins
  • Proteome

Grant support

This work was supported by Fondazione Cariplo (Grant no. 2010-0653) to P.S., MIUR-Regione Lombardia (ID 30190679) to A.P. and G.D., Regione Lombardia “Cooperazione scientifica e tecnologica internazionale” (Grant 16876 SAL-18), Fondazione Banca del Monte di Lombardia and MIUR-PRIN 2012 (2012WJSX8K) to A.P. P.L.M. thanks the Italian Ministry of Economy and Finance, in particular the Project of CNR “FaReBio di Qualità.” The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.