title: The Absence of a Mature Cell Wall Sacculus in Stable Listeria monocytogenes L-Form Cells Is Independent of Peptidoglycan Synthesis.
abstract: L-forms are cell wall-deficient variants of otherwise walled bacteria that maintain the ability to survive and proliferate in absence of the surrounding peptidoglycan sacculus. While transient or unstable L-forms can revert to the walled state and may still rely on residual peptidoglycan synthesis for multiplication, stable L-forms cannot revert to the walled form and are believed to propagate in the complete absence of peptidoglycan. L-forms are increasingly studied as a fundamental biological model system for cell wall synthesis. Here, we show that a stable L-form of the intracellular pathogen Listeria monocytogenes features a surprisingly intact peptidoglycan synthesis pathway including glycosyl transfer, in spite of the accumulation of multiple mutations during prolonged passage in the cell wall-deficient state. Microscopic and biochemical analysis revealed the presence of peptidoglycan precursors and functional glycosyl transferases, resulting in the formation of peptidoglycan polymers but without the synthesis of a mature cell wall sacculus. In conclusion, we found that stable, non-reverting L-forms, which do not require active PG synthesis for proliferation, may still continue to produce aberrant peptidoglycan.
authors.affiliation: Institute for Food, Nutrition and Health, ETH Zurich, Zurich, Switzerland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Studer
authors.affiliation: Department of Microbiology/Biotechnology, University of Tuebingen, Tuebingen, Germany.
authors.forename: Marina
authors.initials: M
authors.lastname: Borisova
authors.affiliation: Department of Microbiology/Biotechnology, University of Tuebingen, Tuebingen, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Schneider
authors.affiliation: Centro de Biología Molecular Severo Ochoa, Universidad Autónoma de Madrid, Madrid, Spain.
authors.forename: Juan A
authors.initials: JA
authors.lastname: Ayala
authors.affiliation: Department of Microbiology/Biotechnology, University of Tuebingen, Tuebingen, Germany.
authors.forename: Christoph
authors.initials: C
authors.lastname: Mayer
authors.affiliation: Institute for Food, Nutrition and Health, ETH Zurich, Zurich, Switzerland.
authors.forename: Markus
authors.initials: M
authors.lastname: Schuppler
authors.affiliation: Institute for Food, Nutrition and Health, ETH Zurich, Zurich, Switzerland.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Loessner
authors.affiliation: Institute for Food, Nutrition and Health, ETH Zurich, Zurich, Switzerland.|Department of Applied Biosciences, Ghent University, Ghent, Belgium.
authors.forename: Yves
authors.identifier: 0000-0001-7723-1040
authors.initials: Y
authors.lastname: Briers
mesh_terms: D002473:Cell Wall / Q000378:metabolism*; D007740:L Forms / Q000378:metabolism*; D008089:Listeria monocytogenes / Q000378:metabolism*; D010457:Peptidoglycan / Q000378:metabolism*; D014166:Transferases / Q000378:metabolism
chemical_list: D010457:Peptidoglycan; D014166:Transferases