The Effect of Lead on the Antimicrobial and Phytochemical Activity of Thymus vulgaris L.

Thyme is a medicinal plant with abundant phenol compounds that has antimicrobial and antioxidant properties and is also used in food industry and household uses. The aim of this study was to investigate the impact of Lead on the antimicrobial properties of thyme and the changes in the amount of the essential oil compounds. Antimicrobial activity was evaluated by measuring the zone of inhibition using disc diffusion method and the MIC values were determined for bacteria of Bacillus subtilis, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli that were sensitive to the essential oil. The findings of this study showed that the amount of thymol in the plants treated with Lead decreased 22% in comparison with the control group plants and the biosynthesis of carvacrol was stopped by Lead stress. The diameter of the zone of growth inhibition for essential oil samples containing Lead decreased in all gram-negative bacteria used in this study, but the minimum inhibitory concentration of essential oil of under stress plants was more than the control. The effect of the essential oil of control plants on the growth of B. subtilis and S. aureus bacteria was more in comparison with the antibiotic gentamicin, while the essential oil of plants treated with Lead showed weaker performance compared to the gentamicin.