Effect of Gamma Radiation and Oregano Essential Oil on Murein and ATP Concentration of Listeria monocytogenes

Authors: Caillet, Stéphane1; Lacroix, Monique1

Source: Journal of Food Protection®, Volume 69, Number 12, December 2006 , pp. 2961-2969(9)

Publisher: International Association for Food Protection

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Abstract:

The effects of gamma radiation and of oregano essential oil alone or in combination with radiation on murein composition of Listeria monocytogenes and on the intracellular and extracellular concentration of ATP were evaluated. The bacterial strain was treated with two radiation doses, 1.2 kGy to induce cell damage and 3.5 kGy to cause cell death. Oregano essential oil was used at 0.020 and 0.025% (wt/vol), which is the MIC. All treatments had a significant effect (P ≤ 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 correlation (P ≤ 0.05) 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, but irradiation of L. monocytogenes alone induced a significant decrease (P ≤ 0.05) of the internal ATP without affecting the external ATP. Transmission electron microscopic observation revealed that oregano oil and irradiation have an effect on cell wall structure.

Document Type: Research article

Affiliations: 1: Canadian Irradiation Center (CIC), 531 Boulevard des Prairies, Laval, Québec, Canada H7V 1B7; Research Laboratory in Sciences Applied to Food, Institut national de la recherche scientifique (INRS)-Institut Armand-Frappier, Université du Québec, 531 Boulevard des Prairies, Laval, Québec, Canada H7V 1B7

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