Dependence of induction of enterobacterial AmpC beta-lactamase on cell-wall peptidoglycan, as demonstrated in Proteus mirabilis and its wall-less protoplast L-form.
The mobilizable plasmid pMD101 (ampR, ampC) was constructed by inserting cloned ampC, the structural gene for the chromosomal AmpC beta-lactamase of Citrobacter freundii, and the closely linked ampR encoding the transcriptional regulator essential for enzyme induction, into the broad host-range plasmid pKT231. Plasmid pMD101 was transconjugated into Proteus mirabilis VI and its isogenic, cell-wall-less protoplast L-form LVI. AmpC beta-lactamase was expressed constitutively from cloned ampR and ampC in bacteria and in some L-form protoplasts. However, induction of the enzyme by beta-lactam antibiotics occurred only in bacterial cells and not in the cell-wall- and peptidoglycan-deficient L-form. In agreement with current models, induction of AmpC beta-lactamase is thought to be initiated by an induction signal arising from the metabolic disturbance of cell-wall peptidoglycan.
Tölg
M
M
Institut für Mikrobiologie, Technische Hochschule Darmstadt, FRG.
Schmidt
H
H
Schierl
R
R
Datz
M
M
Martin
H H
HH
D001426:Bacterial Proteins; D002473:Cell Wall / Q000378:metabolism; D016971:Citrobacter freundii / Q000235:genetics; D003001:Cloning, Molecular; D003227:Conjugation, Genetic; D004790:Enzyme Induction / Q000502:physiology; D010457:Peptidoglycan / Q000378:metabolism*; D011513:Proteus mirabilis / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D011523:Protoplasts / Q000378:metabolism; D001618:beta-Lactamases / Q000096:biosynthesis* / Q000235:genetics
D001426:Bacterial Proteins; D010457:Peptidoglycan; C048795:AmpC beta-lactamases; D001618:beta-Lactamases