title: Spectral snapshots of bacterial cell-wall composition and the influence of antibiotics by whole-cell NMR.
abstract: Gram-positive bacteria surround themselves with a thick cell wall that is essential to cell survival and is a major target of antibiotics. Quantifying alterations in cell-wall composition are crucial to evaluating drug modes of action, particularly important for human pathogens that are now resistant to multiple antibiotics such as Staphylococcus aureus. Macromolecular and whole-cell NMR spectroscopy allowed us to observe the full panel of carbon and nitrogen pools in S. aureus cell walls and intact whole cells. We discovered that one-dimensional (13)C and (15)N NMR spectra, together with spectroscopic selections based on dipolar couplings as well as two-dimensional spin-diffusion measurements, revealed the dramatic compositional differences between intact cells and cell walls and allowed the identification of cell-wall signatures in whole-cell samples. Furthermore, the whole-cell NMR approach exhibited the sensitivity to detect distinct compositional changes due to treatment with the antibiotics fosfomycin (a cell-wall biosynthesis inhibitor) and chloramphenicol (a protein synthesis inhibitor). Whole cells treated with fosfomycin exhibited decreased peptidoglycan contributions while those treated with chloramphenicol contained a higher percentage of peptidoglycan as cytoplasmic protein content was reduced. Thus, general antibiotic modes of action can be identified by profiling the total carbon pools in intact whole cells.
authors: Department of Chemistry, Stanford University, Stanford, California.
authors: Rie
authors: R
authors: Nygaard
authors: Department of Chemistry, Stanford University, Stanford, California.
authors: Joseph A H
authors: JAH
authors: Romaniuk
authors: Department of Chemistry, Stanford University, Stanford, California.
authors: David M
authors: DM
authors: Rice
authors: Department of Chemistry, Stanford University, Stanford, California. Electronic address: cegelski@stanford.edu.
authors: Lynette
authors: L
authors: Cegelski
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002244:Carbon / Q000032:analysis; D002473:Cell Wall / Q000737:chemistry* / Q000187:drug effects*; D002701:Chloramphenicol / Q000494:pharmacology; D005578:Fosfomycin / Q000494:pharmacology; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D009584:Nitrogen / Q000032:analysis; D010457:Peptidoglycan / Q000032:analysis; D011135:Polysaccharides, Bacterial / Q000032:analysis; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology; D011523:Protoplasts / Q000737:chemistry; D013211:Staphylococcus aureus / Q000737:chemistry* / Q000187:drug effects*; D013682:Teichoic Acids / Q000032:analysis
chemical_list: D000900:Anti-Bacterial Agents; D010457:Peptidoglycan; D011135:Polysaccharides, Bacterial; D011500:Protein Synthesis Inhibitors; D013682:Teichoic Acids; D005578:Fosfomycin; D002701:Chloramphenicol; D002244:Carbon; D009584:Nitrogen