The signal molecule for beta-lactamase induction in Enterobacter cloacae is the anhydromuramyl-pentapeptide.
Beta-lactamase induction in Enterobacter cloacae, which is linked to peptidoglycan recycling, was investigated by high-performance liquid chromatographic analysis of cell wall fragments in genetically defined cells of Escherichia coli. After treatment of cells with beta-lactams, we detected an increase in a D-tripeptide (disaccharide-tripeptide, N-acetylglucosaminyl-1,6-anhydro-N-acetylmuramyl-L-alanyl-D-glutamyl-mes o-diaminopimelic acid), aD-tetrapeptide (disaccharide-tetrapeptide, N-acetylglucosaminyl-1,6-anhydro-N-acetylmuramyl-L-alanyl-D-glutamyl-mes o-diaminopimelic acid-D-alanine), and aD-pentapeptide (disaccharide-pentapeptide, N-acetylglucosaminyl-1,6-anhydro-N-acetylmuramyl-L-alanyl-D-glutamyl-mes o-diaminopimelic acid-D-alanyl-D-alanine)levels in the periplasms of bacterial cells. Furthermore, only the accumulation of aD-pentapeptide correlates with the beta-lactamase-inducing capacity of the beta-lactam antibiotic. The transmembrane protein AmpG transports all three aD-peptides into the cytoplasm, where they are degraded into the corresponding monosaccharide peptides. In the absence of AmpD the constitutive overproduction of beta-lactamase is accompanied by an accumulation of aM-tripeptide (monosaccharide-tripeptide, anhydro-N-acetylmuramyl-L-alanyl-D-glutamyl-meso-diaminopimelic acid) and aM-pentapeptide (L1,6-anhydro-N-acetylmuramyl-L-alanyl-D-glutamyl-meso-diaminopimelic acid-D-alanyl-D-alanine), but not aM-tetrapeptide (anhydro-N-acetylmuramyl-L-alanyl-D-glutamyl-meso-diaminopimelic acid-D-alanine), in the cytoplasm. Only the amount of aM-pentapeptide is increased upon treatment with imipenem. These findings indicate that aD-pentapeptide is the main periplasmic muropeptide, which is converted into the cytoplasmic signal molecule for beta-lactamase induction, the aM-pentapeptide.
Dietz
H
H
Institut für Medizinische Mikrobiologie und Immunologie, University of Bonn, Germany.
Pfeifle
D
D
Wiedemann
B
B
D000119:Acetylmuramyl-Alanyl-Isoglutamine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002473:Cell Wall / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D003593:Cytoplasm / Q000737:chemistry; D004269:DNA, Bacterial / Q000096:biosynthesis / Q000235:genetics; D004754:Enterobacter / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D004790:Enzyme Induction / Q000187:drug effects; D015378:Imipenem / Q000494:pharmacology; D013058:Mass Spectrometry; D000432:Methanol / Q000737:chemistry; D010457:Peptidoglycan / Q000378:metabolism; D010957:Plasmids / Q000235:genetics; D021382:Protein Sorting Signals / Q000494:pharmacology*; D001618:beta-Lactamases / Q000096:biosynthesis*
D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D010457:Peptidoglycan; D021382:Protein Sorting Signals; C052167:1,6-anhydromuramyl-alanyl-glutamyl-diaminopimelyl-alanine; D000119:Acetylmuramyl-Alanyl-Isoglutamine; D015378:Imipenem; D001618:beta-Lactamases; D000432:Methanol