title: Cell growth of wall-free L-form bacteria is limited by oxidative damage.
abstract: The peptidoglycan (PG) cell wall is a defining feature of the bacterial lineage and an important target for antibiotics, such as β-lactams and glycopeptides. Nevertheless, many bacteria are capable of switching into a cell-wall-deficient state, called the "L-form" [1-3]. These variants have been classically identified as antibiotic-resistant forms in association with a wide range of infectious diseases [4]. L-forms become completely independent of the normally essential FtsZ cell division machinery [3, 5]. Instead, L-form proliferation is driven by a simple biophysical process based on an increased ratio of surface area to cell volume synthesis [6, 7]. We recently showed that only two genetic changes are needed for the L-form transition in Bacillus subtilis [7]. Class 1 mutations work to generate excess membrane synthesis [7]. Until now, the function of the class 2 mutations was unclear. We now show that these mutations work by counteracting an increase in the cellular levels of reactive oxygen species (ROS) originating from the electron transport pathway, which occurs in wall-deficient cells. Consistent with this, addition of a ROS scavenger or anaerobic culture conditions also worked to promote L-form growth without the class 2 mutations in both Gram-positive B. subtilis and Gram-negative Escherichia coli. Our results suggest that physiological compensation for the metabolic imbalance that occurs when cell wall synthesis is blocked is crucial for L-form proliferation in a wide range of bacteria and also provide new insights into the mode of action of antibiotics that target the bacterial cell wall.
authors.affiliation: Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Medical School, Newcastle University, Richardson Road, Newcastle upon Tyne NE2 4AX, UK. Electronic address: y.kawai@ncl.ac.uk.
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Kawai
authors.affiliation: Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Medical School, Newcastle University, Richardson Road, Newcastle upon Tyne NE2 4AX, UK.
authors.forename: Romain
authors.initials: R
authors.lastname: Mercier
authors.affiliation: Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Medical School, Newcastle University, Richardson Road, Newcastle upon Tyne NE2 4AX, UK.
authors.forename: Ling Juan
authors.initials: LJ
authors.lastname: Wu
authors.affiliation: Department of Biology, University of Copenhagen, Ole Maaløes Vej 5, 2200 Copenhagen N, Denmark.
authors.forename: Patricia
authors.initials: P
authors.lastname: Domínguez-Cuevas
authors.affiliation: Genomics of Bacterial Cell Functions, Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5, Takayama, Ikoma, Nara 630-0192, Japan.
authors.forename: Taku
authors.initials: T
authors.lastname: Oshima
authors.affiliation: Centre for Bacterial Cell Biology, Institute for Cell and Molecular Biosciences, Medical School, Newcastle University, Richardson Road, Newcastle upon Tyne NE2 4AX, UK. Electronic address: jeff.errington@ncl.ac.uk.
authors.forename: Jeff
authors.initials: J
authors.lastname: Errington
mesh_terms: D001412:Bacillus subtilis / Q000166:cytology* / Q000235:genetics; D002473:Cell Wall; D004579:Electron Transport; D004926:Escherichia coli / Q000166:cytology*; D007740:L Forms / Q000166:cytology*; D009154:Mutation; D010084:Oxidation-Reduction; D018384:Oxidative Stress