title: The zeamine antibiotics affect the integrity of bacterial membranes.
abstract: The zeamines (zeamine, zeamine I, and zeamine II) constitute an unusual class of cationic polyamine-polyketide-nonribosomal peptide antibiotics produced by Serratia plymuthica RVH1. They exhibit potent bactericidal activity, killing a broad range of Gram-negative and Gram-positive bacteria, including multidrug-resistant pathogens. Examination of their specific mode of action and molecular target revealed that the zeamines affect the integrity of cell membranes. The zeamines provoke rapid release of carboxyfluorescein from unilamellar vesicles with different phospholipid compositions, demonstrating that they can interact directly with the lipid bilayer in the absence of a specific target. DNA, RNA, fatty acid, and protein biosynthetic processes ceased simultaneously at subinhibitory levels of the antibiotics, presumably as a direct consequence of membrane disruption. The zeamine antibiotics also facilitated the uptake of small molecules, such as 1-N-phenylnaphtylamine, indicating their ability to permeabilize the Gram-negative outer membrane (OM). The valine-linked polyketide moiety present in zeamine and zeamine I was found to increase the efficiency of this process. In contrast, translocation of the large hydrophilic fluorescent peptidoglycan binding protein PBDKZ-GFP was not facilitated, suggesting that the zeamines cause subtle perturbation of the OM rather than drastic alterations or defined pore formation. At zeamine concentrations above those required for growth inhibition, membrane lysis occurred as indicated by time-lapse microscopy. Together, these findings show that the bactericidal activity of the zeamines derives from generalized membrane permeabilization, which likely is initiated by electrostatic interactions with negatively charged membrane components.
authors.affiliation: Laboratory of Gene Technology, Department of Biosystems, KU Leuven, Heverlee, Belgium Laboratory of Food Microbiology, Department of Microbial and Molecular Systems, KU Leuven, Heverlee, Belgium.
authors.forename: Joleen
authors.initials: J
authors.lastname: Masschelein
authors.affiliation: Laboratory of Gene Technology, Department of Biosystems, KU Leuven, Heverlee, Belgium Laboratory of Food Microbiology, Department of Microbial and Molecular Systems, KU Leuven, Heverlee, Belgium.
authors.forename: Charlien
authors.initials: C
authors.lastname: Clauwers
authors.affiliation: Laboratory of Gene Technology, Department of Biosystems, KU Leuven, Heverlee, Belgium.
authors.forename: Karen
authors.initials: K
authors.lastname: Stalmans
authors.affiliation: Molecular Design and Synthesis, Department of Chemistry, KU Leuven, Heverlee, Belgium.
authors.forename: Koen
authors.initials: K
authors.lastname: Nuyts
authors.affiliation: Molecular Design and Synthesis, Department of Chemistry, KU Leuven, Heverlee, Belgium.
authors.forename: Wim
authors.initials: W
authors.lastname: De Borggraeve
authors.affiliation: Laboratory of Gene Technology, Department of Biosystems, KU Leuven, Heverlee, Belgium.
authors.forename: Yves
authors.initials: Y
authors.lastname: Briers
authors.affiliation: Laboratory of Food Microbiology, Department of Microbial and Molecular Systems, KU Leuven, Heverlee, Belgium.
authors.forename: Abram
authors.initials: A
authors.lastname: Aertsen
authors.affiliation: Laboratory of Food Microbiology, Department of Microbial and Molecular Systems, KU Leuven, Heverlee, Belgium.
authors.forename: Chris W
authors.initials: CW
authors.lastname: Michiels
authors.affiliation: Laboratory of Gene Technology, Department of Biosystems, KU Leuven, Heverlee, Belgium rob.lavigne@biw.kuleuven.be.
authors.forename: Rob
authors.initials: R
authors.lastname: Lavigne
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects* / Q000502:physiology; D004247:DNA / Q000096:biosynthesis; D004926:Escherichia coli / Q000187:drug effects*; D018942:Macrolides / Q000378:metabolism / Q000494:pharmacology*; D053858:Metabolic Networks and Pathways / Q000187:drug effects; D050296:Microbial Viability / Q000187:drug effects*; D008958:Models, Molecular; D008968:Molecular Conformation; D010539:Permeability / Q000187:drug effects*; D011073:Polyamines / Q000378:metabolism / Q000494:pharmacology*; D014176:Protein Biosynthesis / Q000187:drug effects; D012705:Serratia / Q000378:metabolism; D013211:Staphylococcus aureus / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D018942:Macrolides; D011073:Polyamines; C547236:zeamine; D004247:DNA