title: Modification of Salmonella Lipopolysaccharides Prevents the Outer Membrane Penetration of Novobiocin.
abstract: Small hydrophilic antibiotics traverse the outer membrane of Gram-negative bacteria through porin channels. Large lipophilic agents traverse the outer membrane through its bilayer, containing a majority of lipopolysaccharides in its outer leaflet. Genes controlled by the two-component regulatory system PhoPQ modify lipopolysaccharides. We isolate lipopolysaccharides from isogenic mutants of Salmonella sp., one lacking the modification, the other fully modified. These lipopolysaccharides were reconstituted as monolayers at the air-water interface, and their properties, as well as their interaction with a large lipophilic drug, novobiocin, was studied. X-ray reflectivity showed that the drug penetrated the monolayer of the unmodified lipopolysaccharides reaching the hydrophobic region, but was prevented from this penetration into the modified lipopolysaccharides. Results correlate with behavior of bacterial cells, which become resistant to antibiotics after PhoPQ-regulated modifications. Grazing incidence x-ray diffraction showed that novobiocin produced a striking increase in crystalline coherence length, and the size of the near-crystalline domains.
authors.affiliation: Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California; Molecular Foundry, Lawrence Berkeley National Laboratory, Berkeley, California. Electronic address: thatty@ursa.ifsc.usp.br.
authors.forename: Thatyane M
authors.initials: TM
authors.lastname: Nobre
authors.affiliation: Center for Molecular Study of Condensed Soft Matter and Department of Physics, Illinois Institute of Technology, Chicago, Illinois; X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Martynowycz
authors.affiliation: Center for Molecular Study of Condensed Soft Matter and Department of Physics, Illinois Institute of Technology, Chicago, Illinois.
authors.forename: Konstantin
authors.initials: K
authors.lastname: Andreev
authors.affiliation: X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois.
authors.forename: Ivan
authors.initials: I
authors.lastname: Kuzmenko
authors.affiliation: Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, California.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nikaido
authors.affiliation: Center for Molecular Study of Condensed Soft Matter and Department of Physics, Illinois Institute of Technology, Chicago, Illinois. Electronic address: gidalevitz@iit.edu.
authors.forename: David
authors.initials: D
authors.lastname: Gidalevitz
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D008050:Lipid A / Q000378:metabolism; D008070:Lipopolysaccharides / Q000378:metabolism*; D009675:Novobiocin / Q000737:chemistry / Q000378:metabolism / Q000494:pharmacology*; D010539:Permeability; D012475:Salmonella / Q000166:cytology* / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D008050:Lipid A; D008070:Lipopolysaccharides; D009675:Novobiocin