title: Unstable Escherichia coli L forms revisited: growth requires peptidoglycan synthesis.
abstract: Growing bacterial L forms are reputed to lack peptidoglycan, although cell division is normally inseparable from septal peptidoglycan synthesis. To explore which cell division functions L forms use, we established a protocol for quantitatively converting a culture of a wild-type Escherichia coli K-12 strain overnight to a growing L-form-like state by use of the beta-lactam cefsulodin, a specific inhibitor of penicillin-binding proteins (PBPs) 1A and 1B. In rich hypertonic medium containing cefsulodin, all cells are spherical and osmosensitive, like classical L forms. Surprisingly, however, mutant studies showed that colony formation requires d-glutamate, diaminopimelate, and MurA activity, all of which are specific to peptidoglycan synthesis. High-performance liquid chromatography analysis confirmed that these L-form-like cells contain peptidoglycan, with 7% of the normal amount. Moreover, the beta-lactam piperacillin, a specific inhibitor of the cell division protein PBP 3, rapidly blocks the cell division of these L-form-like cells. Similarly, penicillin-induced L-form-like cells, which grow only within the agar layers of rich hypertonic plates, also require d-glutamate, diaminopimelate, and MurA activity. These results strongly suggest that cefsulodin- and penicillin-induced L-form-like cells of E. coli-and possibly all L forms-have residual peptidoglycan synthesis which is essential for their growth, probably being required for cell division.
authors.affiliation: Institut Jacques Monod, 2 place Jussieu, 75251 Paris Cedex 05, France. dari@ijm.jussieu.fr
authors.forename: Danièle
authors.initials: D
authors.lastname: Joseleau-Petit
authors.forename: Jean-Claude
authors.initials: JC
authors.lastname: Liébart
authors.forename: Juan A
authors.initials: JA
authors.lastname: Ayala
authors.forename: Richard
authors.initials: R
authors.lastname: D'Ari
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002441:Cefsulodin / Q000494:pharmacology; D002455:Cell Division; D002473:Cell Wall / Q000737:chemistry; D003470:Culture Media; D004926:Escherichia coli / Q000187:drug effects / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D007740:L Forms / Q000187:drug effects / Q000254:growth & development*; D009154:Mutation; D010457:Peptidoglycan / Q000096:biosynthesis*; D010878:Piperacillin / Q000494:pharmacology; D047090:beta-Lactams / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D003470:Culture Media; D010457:Peptidoglycan; D047090:beta-Lactams; D002441:Cefsulodin; D010878:Piperacillin