title: Modification of the peptidoglycan of Escherichia coli in the viable but nonculturable state.
abstract: The aim of this study was to analyse the chemical composition of peptidoglycan and the state of some of the enzymes involved in its metabolism in Escherichia coli KN126 in the viable but nonculturable (VBNC) state which is a survival strategy adopted by bacteria (including those of medical interest) when exposed to environmental stresses. When entering the VBNC state, E. coli cells miniaturised and became coccus-shaped. Analysis of peptidoglycan chemical composition, by separation in HPLC of muropeptides released by muramidase digestion of purified peptidoglycan, indicated a high degree of cross-linking, a threefold increase in unusual DAP-DAP cross-linking, an increase in muropeptides bearing covalently bound lipoprotein, and a shortening of the average length of glycan strands in comparison with dividing cells. Analysis of penicillin-binding proteins (PBPs), enzymes involved in the terminal stage of peptidoglycan assembly showed the disappearance of high-molecular-weight PBPs 1A, 1B, 2, and 3 in VBNC cells. Finally, VBNC cells displayed an autolytic capability which was far higher than that of exponentially growing cells. It is suggested that part of these alterations of peptidoglycan may be connected with the VBNC state.
authors.affiliation: Dipartimento di Patologia, Sezione di Microbiologia, Università di Verona, Strada Le Grazie, 8, 37134 Verona, Italy.
authors.forename: Caterina
authors.initials: C
authors.lastname: Signoretto
authors.forename: Maria  Mar
authors.initials: M
authors.lastname: Lleò
authors.forename: Pietro
authors.initials: P
authors.lastname: Canepari
mesh_terms: D000942:Antigens, Bacterial; D001426:Bacterial Proteins / Q000378:metabolism; D001433:Bacteriolysis; D002352:Carrier Proteins / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D004926:Escherichia coli / Q000201:enzymology* / Q000254:growth & development / Q000378:metabolism; D006602:Hexosyltransferases; D009113:Muramidase / Q000378:metabolism*; D002267:Muramoylpentapeptide Carboxypeptidase / Q000378:metabolism; D046915:Penicillin-Binding Proteins; D010457:Peptidoglycan / Q000737:chemistry / Q000378:metabolism*; D010458:Peptidyl Transferases
chemical_list: D000942:Antigens, Bacterial; D001426:Bacterial Proteins; D002352:Carrier Proteins; C421489:MRP protein, Streptococcus suis; D046915:Penicillin-Binding Proteins; D010457:Peptidoglycan; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D009113:Muramidase; D002267:Muramoylpentapeptide Carboxypeptidase