Metabolite profiling and peptidoglycan analysis of transient cell wall-deficient bacteria in a new Escherichia coli model system

• Published in: Environmental microbiology 2015-05, Vol.17 (5), p.1586-1599
• Main Authors: Cambré, Alexander, Zimmermann, Michael, Sauer, Uwe, Vivijs, Bram, Cenens, William, Michiels, Chris W., Aertsen, Abram, Loessner, Martin J., Noben, Jean-Paul, Ayala, Juan A., Lavigne, Rob, Briers, Yves
• Format: Article
• Language: English
• Subjects: Bacteriology; beta-Lactam Resistance - genetics; beta-Lactams - pharmacology; Cell Wall - metabolism; E coli; Escherichia coli - drug effects; Escherichia coli - genetics; Escherichia coli - metabolism; Escherichia coli Proteins - biosynthesis; Escherichia coli Proteins - genetics; Gene Library; Membrane Lipids - metabolism; Models, Biological; Penicillin-Binding Proteins - biosynthesis; Penicillin-Binding Proteins - genetics; Peptidoglycan - metabolism; Serine-Type D-Ala-D-Ala Carboxypeptidase - biosynthesis; Serine-Type D-Ala-D-Ala Carboxypeptidase - genetics
• ISSN: 1462-2912; 1462-2920
• DOI: 10.1111/1462-2920.12594

Summary Many bacteria are able to assume a transient cell wall‐deficient (or L‐form) state under favourable osmotic conditions. Cell wall stress such as exposure to β‐lactam antibiotics can enforce the transition to and maintenance of this state. L‐forms actively proliferate and can return to the walled state upon removal of the inducing agent. We have adopted Escherichia coli as a model system for the controlled transition to and reversion from the L‐form state, and have studied these dynamics with genetics, cell biology and ‘omics’ technologies. As such, a transposon mutagenesis screen underscored the requirement for the Rcs phosphorelay and colanic acid synthesis, while proteomics show only little differences between rods and L‐forms. In contrast, metabolome comparison reveals the high abundance of lysophospholipids and phospholipids with unsaturated or cyclopropanized fatty acids in E. coli L‐forms. This increase of membrane lipids associated with increased membrane fluidity may facilitate proliferation through bud formation. Visualization of the residual peptidoglycan with a fluorescently labelled peptidoglycan binding protein indicates de novo cell wall synthesis and a role for septal peptidoglycan synthesis during bud constriction. The DD‐carboxypeptidases PBP5 and PBP6 are threefold and fourfold upregulated in L‐forms, indicating a specific role for regulation of crosslinking during L‐form proliferation.