title: How methylglyoxal kills bacteria: An ultrastructural study.
abstract: Antibacterial activity of honey is due to the presence of methylglyoxal (MGO), H2O2, bee defensin as well as polyphenols. High MGO levels in manuka honey are the main source of antibacterial activity. Manuka honey has been reported to reduce the swarming and swimming motility of Pseudomonas aeruginosa due to de-flagellation. Due to the complexity of honey it is unknown if this effect is directly due to MGO. In this ultrastructural investigation the effects of MGO on the morphology of bacteria and specifically the structure of fimbriae and flagella were investigated. MGO effectively inhibited Gram positive (Bacillus subtilis; MIC 0.8 mM and Staphylococcus aureus; MIC 1.2 mM) and Gram negative (P. aeruginosa; MIC 1.0 mM and Escherichia coli; MIC 1.2 mM) bacteria growth. The ultrastructural effects of 0.5, 1.0 and 2 mM MGO on B. substilis and E. coli morphology was then evaluated. At 0.5 mM MGO, bacteria structure was unaltered. For both bacteria at 1 mM MGO fewer fimbriae were present and the flagella were less or absent. Identified structures appeared stunted and fragile. At 2 mM MGO fimbriae and flagella were absent while the bacteria were rounded with shrinkage and loss of membrane integrity. Antibacterial MGO causes alterations in the structure of bacterial fimbriae and flagella which would limit bacteria adherence and motility.
authors.affiliation: a Department of Anatomy, Faculty of Health Sciences , University of Pretoria , Arcadia , South Africa.
authors.forename: Erika
authors.initials: E
authors.lastname: Rabie
authors.affiliation: a Department of Anatomy, Faculty of Health Sciences , University of Pretoria , Arcadia , South Africa.
authors.forename: June Cheptoo
authors.initials: JC
authors.lastname: Serem
authors.affiliation: a Department of Anatomy, Faculty of Health Sciences , University of Pretoria , Arcadia , South Africa.
authors.forename: Hester Magdalena
authors.initials: HM
authors.lastname: Oberholzer
authors.affiliation: b Department of Biochemistry, Faculty of Natural and Agricultural Sciences , University of Pretoria , Arcadia , South Africa.
authors.forename: Anabella Regina Marques
authors.initials: AR
authors.lastname: Gaspar
authors.affiliation: a Department of Anatomy, Faculty of Health Sciences , University of Pretoria , Arcadia , South Africa.
authors.forename: Megan Jean
authors.initials: MJ
authors.lastname: Bester
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001412:Bacillus subtilis / Q000187:drug effects / Q000648:ultrastructure; D001422:Bacterial Adhesion / Q000187:drug effects; D004926:Escherichia coli / Q000187:drug effects / Q000648:ultrastructure; D010861:Fimbriae, Bacterial / Q000187:drug effects / Q000648:ultrastructure; D005407:Flagella / Q000187:drug effects / Q000648:ultrastructure; D006090:Gram-Negative Bacteria / Q000187:drug effects* / Q000648:ultrastructure; D006094:Gram-Positive Bacteria / Q000187:drug effects* / Q000648:ultrastructure; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D008855:Microscopy, Electron, Scanning; D011550:Pseudomonas aeruginosa / Q000187:drug effects / Q000648:ultrastructure; D011765:Pyruvaldehyde / Q000494:pharmacology*; D013211:Staphylococcus aureus / Q000187:drug effects / Q000648:ultrastructure
chemical_list: D000900:Anti-Bacterial Agents; D011765:Pyruvaldehyde
keywords: Antibacterial; fimbriae; flagella; methylglyoxal