title: Identification of MupP as a New Peptidoglycan Recycling Factor and Antibiotic Resistance Determinant inPseudomonas aeruginosa.
abstract: Peptidoglycan (PG) is an essential cross-linked polymer that surrounds most bacterial cells to prevent osmotic rupture of the cytoplasmic membrane. Its synthesis relies on penicillin-binding proteins, the targets of beta-lactam antibiotics. Many Gram-negative bacteria, including the opportunistic pathogenPseudomonas aeruginosa, are resistant to beta-lactams because of a chromosomally encoded beta-lactamase called AmpC. InP. aeruginosa, expression of theampCgene is tightly regulated and its induction is linked to cell wall stress. We reasoned that a reporter gene fusion to theampCpromoter would allow us to identify mutants defective in maintaining cell wall homeostasis and thereby uncover new factors involved in the process. A library of transposon-mutagenizedP. aeruginosawas therefore screened for mutants with elevatedampCpromoter activity. As an indication that the screen was working as expected, mutants with transposons disrupting thedacBgene were isolated. Defects in DacB have previously been implicated inampCinduction and clinical resistance to beta-lactam antibiotics. The screen also uncoveredmurUandPA3172mutants that, upon further characterization, displayed nearly identical drug resistance and sensitivity profiles. We present genetic evidence thatPA3172, renamedmupP, encodes the missing phosphatase predicted to function in the MurU PG recycling pathway that is widely distributed among Gram-negative bacteria.IMPORTANCEThe cell wall biogenesis pathway is the target of many of our best antibiotics, including penicillin and related beta-lactam drugs. Resistance to these therapies is on the rise, particularly among Gram-negative species likePseudomonas aeruginosa, a problematic opportunistic pathogen. To better understand how these organisms resist cell wall-targeting antibiotics, we screened forP. aeruginosamutants defective in maintaining cell wall homeostasis. The screen identified a new factor, called MupP, involved in the recycling of cell wall turnover products. Characterization of MupP and other components of the pathway revealed that cell wall recycling plays important roles in both the resistance and the sensitivity ofP. aeruginosato cell wall-targeting antibiotics.
authors.affiliation: Department of Microbiology and Immunobiology, Harvard Medical School, Boston, USA.
authors.forename: Coralie
authors.initials: C
authors.lastname: Fumeaux
authors.affiliation: Department of Microbiology and Immunobiology, Harvard Medical School, Boston, USA thomas_bernhardt@hms.harvard.edu.
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Bernhardt
mesh_terms: D002473:Cell Wall / Q000378:metabolism*; D004251:DNA Transposable Elements; D024881:Drug Resistance, Bacterial; D016254:Mutagenesis, Insertional; D010457:Peptidoglycan / Q000378:metabolism*; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism*; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*
chemical_list: D004251:DNA Transposable Elements; D010457:Peptidoglycan; D010744:Phosphoric Monoester Hydrolases