Poster Presentation BACPATH 2019

The Gram-negative bacterial periplasm; Architecture significance (#128)

Eric Mandela 1 , Von L Torres 1 , Christopher J Stubenrauch 1 , Chaille T Webb 1 , Cheng E Huang 2 , Ralf Schittenhelm 2 , JC Gumbart 3 , Iain D Hay 4 , Trevor Lithgow 1
  1. Infection and Immunity Program , Biomedicine Discovery Institute and Department of Microbiology, Monash University, , Clayton, Victoria, Australia
  2. Monash Proteomic & Metabolomic Facility,, Clayton, 3800, Australia , Monash University, Clayton, VIC, Australia
  3. School of Physics, , Georgia Institute of Technology,, Atlanta, , Georgia, USA
  4. Biological sciences , University of Auckland, , Auckland, New Zealand

Here we investigated the key player in the bacterial cell envelope organization; a small, alpha-helical lipoprotein protein Lpp, AKA Braun’s lipoprotein. Lpp provides the only covalent connection between the outer membrane (OM) and the peptidoglycan (PG). The N-terminus is attached to the OM while the C-terminus is attached to the PG. Recent work has shown that the width of the periplasm is controlled largely by Lpp. Lengthening of Lpp allowed the expansion of the periplasm relative to the number of heptad repeats inserted within the Lpp sequence.

The bacterial cell envelope is the interface through which bacteria interact with their environment, everything going into or out of the cell must transit it, and many important cellular functions take place within its enclosed periplasm: cell division regulation, osmoregulation, peptidoglycan synthesis, multidrug efflux systems, and many others. we sought to use a synthetic lethal genetic screening approach to identify periplasmic processes that are dependent on the periplasmic architecture. In addition, RNAseq and proteomics studies were performed on the lengthened Lpp isoform.  Here we report the effect of a widened periplasm on peptidoglycan assembly. The activation of the major penicillin binding proteins (PBP1A and PBP1B) by their cognate lipoproteins (LpoA and LpoB) is compromised which leads to synthetic lethal phenotype when either of the redundant pathway is removed. We also show the significance of OmpA, Pal, and TolC in non-covalent binding of the PG. The data also shows compromised iron import and lipopolysaccharide (LPS) trafficking across the periplasm. These genetic screen results are further studied to better understand the coordination between the OM and PG biogenesis in bacterial cell elongation.

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  2. Asmar AT, Ferreira JL, Cohen EJ, Cho SH, Beeby M, Hughes KT, et al. Communication across the bacterial cell envelope depends on the size of the periplasm. PLoS Biol. 2017;15(12):e2004303.