title: Amino acid addition to Vibrio cholerae LPS establishes a link between surface remodeling in gram-positive and gram-negative bacteria.
abstract: Historically, the O1 El Tor and classical biotypes of Vibrio cholerae have been differentiated by their resistance to the antimicrobial peptide polymyxin B. However, the molecular mechanisms associated with this phenotypic distinction have remained a mystery for 50 y. Both gram-negative and gram-positive bacteria modify their cell wall components with amine-containing substituents to reduce the net negative charge of the bacterial surface, thereby promoting cationic antimicrobial peptide resistance. In the present study, we demonstrate that V. cholerae modify the lipid A anchor of LPS with glycine and diglycine residues. This previously uncharacterized lipid A modification confers polymyxin resistance in V. cholerae El Tor, requiring three V. cholerae proteins: Vc1577 (AlmG), Vc1578 (AlmF), and Vc1579 (AlmE). Interestingly, the protein machinery required for glycine addition is reminiscent of the gram-positive system responsible for D-alanylation of teichoic acids. Such machinery was not thought to be used by gram-negative organisms. V. cholerae O1 El Tor mutants lacking genes involved in transferring glycine to LPS showed a 100-fold increase in sensitivity to polymyxin B. This work reveals a unique lipid A modification and demonstrates a charge-based remodeling strategy shared between gram-positive and gram-negative organisms.
authors.affiliation: Section of Molecular Genetics and Microbiology, University of Texas, Austin, TX 78712, USA.
authors.forename: Jessica V
authors.initials: JV
authors.lastname: Hankins
authors.forename: James A
authors.initials: JA
authors.lastname: Madsen
authors.forename: David K
authors.initials: DK
authors.lastname: Giles
authors.forename: Jennifer S
authors.initials: JS
authors.lastname: Brodbelt
authors.forename: M Stephen
authors.initials: MS
authors.lastname: Trent
mesh_terms: D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D019731:Carbon-Nitrogen Ligases / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002473:Cell Wall / Q000737:chemistry / Q000378:metabolism; D024881:Drug Resistance, Bacterial; D005998:Glycine / Q000737:chemistry / Q000378:metabolism*; D006090:Gram-Negative Bacteria / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D006094:Gram-Positive Bacteria / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008050:Lipid A / Q000737:chemistry / Q000378:metabolism; D008070:Lipopolysaccharides / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D015394:Molecular Structure; D009154:Mutation; D011112:Polymyxin B / Q000494:pharmacology; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D014734:Vibrio cholerae / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D002352:Carrier Proteins; D008050:Lipid A; D008070:Lipopolysaccharides; D019731:Carbon-Nitrogen Ligases; D011112:Polymyxin B; D005998:Glycine