title: Effect of gamma radiation and oregano essential oil on murein and ATP concentration of Staphylococcus aureus.
abstract: The study was carried out to evaluate the effects of gamma-irradiation alone or in combination with oregano essential oil on murein composition of Staphylococcus aureus and on the intracellular and extracellular concentration of ATP. The bacterial strain was treated with 3 irradiation doses: 1.2 kGy to induce cell damage, 2.9 kGy to obtain a viable but nonculturable state, and 3.5 kGy to cause cell death. Oregano essential oil was used at 0.010% and 0.013% (w/v), which is the minimum inhibitory concentration (MIC). All treatments had a significant effect (P < or = 0.05) on the murein composition, although some muropeptides did not seem to be affected by the treatment. Each treatment influenced differently the relative percentage and number of muropeptides. There was a significant (P < or = 0.05) correlation between the reduction of intracellular ATP and increase in extracellular ATP following treatment of the cells with oregano oil. The reduction of intracellular ATP was even more important when essential oil was combined with irradiation. Also, irradiation alone of S. aureus induced a significant decrease (P < or = 0.05) of the internal ATP and a significant increase (P < or = 0.05) of the external ATP. However, no significant difference (P > 0.05) was observed in ATP concentrations between different radiation doses. Transmission electron microscopic observation revealed that oregano oil and irradiation have an effect on cell wall structure.
authors.affiliation: Canadian Irradiation Center and Research Laboratories in Sciences Applied to Food, Canada.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Caillet
authors.forename: Laura
authors.initials: L
authors.lastname: Ursachi
authors.forename: François
authors.initials: F
authors.lastname: Shareck
authors.forename: Monique
authors.initials: M
authors.lastname: Lacroix
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D002473:Cell Wall / Q000187:drug effects / Q000528:radiation effects / Q000648:ultrastructure; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D005519:Food Preservation / Q000379:methods; D005517:Foodborne Diseases / Q000517:prevention & control; D005720:Gamma Rays; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000528:radiation effects; D046529:Microscopy, Electron, Transmission; D009822:Oils, Volatile / Q000494:pharmacology*; D031341:Origanum / Q000737:chemistry*; D010457:Peptidoglycan / Q000302:isolation & purification / Q000378:metabolism*; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000378:metabolism / Q000528:radiation effects* / Q000648:ultrastructure
chemical_list: D009822:Oils, Volatile; D010457:Peptidoglycan; D000255:Adenosine Triphosphate