## 4 Discussion

Table 5: Phenolics composition of ethanolic extract of studied species. Results are reported as the mean \(\pm\) standard deviations (SD) of three measurements. 13 mm to 16 mm for all bacteria. Among the plants that had a high degree of antibacterial activity (MIC = 0.04 mg/mL), the most important were _P. lenticiscus_ and _E. multiiflora_. Concerning BMC, the values were the same or 2 to 4 times higher than the similar or 2 to 4 times higher than the MIC values of EEs. The variation between the activities of the EEs and the standard antimicrobial medicament may be attributed to the combinations of bioactive compounds that exist in the extract as compared to the pure compounds present in the standard antibiotics, which rarely have the same potency as the unrefined extract at comparable concentrations or doses of the active substance [45]. Previous studies had shown that Gram-positive bacterial strains were known to be more sensitive to plant extracts than Gram-negative bacteriores, which are more resistant [46; 47; 48]. This sensitivity is attributed to the availability of hydrophobic lipopolysaccharidesaccharides in the outer membrane of Gram-negative bacteria. Thus, Gram-negative bacteria are more difficult to control due to their double-layered membrane [49]. Furthermore, our results highlight that the EEs were quite effective in controlling the bacteria compared to other previous studies [42; 50]. None of our EEs demonstrated selective antimicrobial activity based on differences in bacterial cell walls. Antimicrobial compounds in EEs of plants can inhibit bacterial growth through different mechanisms. Interactions with hydrophobic structures of bacterial strains had a key role in the antimicrobial actions of secondary plant metabolites [51; 52]. In the present study, _L. monocytogenes_ and _E. coli_ cells were destroyed and killed in the stationary phase of growth (after 2 h) by _P. latifolia_, _R. officinalis_, and _E. multiiflora_ EEs, while _C. villosa_, _E. multiiflora_, and _P. lenticus_ EEs inhibited the growth of _S. aureus_ after 2 h. _S. typhimurium_ was the only bacterium inhibited by all EEs after 4 h. In this growth phase, organisms are generally less susceptible to injury than those in the exponential phase [52]. Antimicrobial agents affecting cell synthesis processes often have little impact on organisms in the stationary phase of growth [53], and these results suggest that that the macromolecular synthesis process was not the primary target of EEs. In recent years, several studies have attempted to identify and explain the mechanisms of action of certain medicinal plant extracts on pathogenic bacterial strains. The essential oils of rosewood, oengano, thyme [54], and tea tree [31] have been described as producing damage to the bacterial membrane and inducing cell lysis. Additionally, the essential oil of _B. pandurata_ has been signaled to affect the membrane permeability of _Escherichia coli_[55]. In the present study, it was demonstrated that treatment of the studied bacterial cells with the studied plant EEs induced cell lysis. This possible mechanism of action may be related to the cell wall and membrane. Certain antimicrobial substances produce significant damage to the membrane and lead to lysis of the whole cell [31]. This phenomenon has been described previously for _Jatropha curcas_, oregano, and thyme EEs [54]. The inability of _Pistacia lentiscus_, _Rosmarinus officinalis_, _Erica multiflora_, _Calicotome villosa_, and _Phillyrea latifolia_ or their components to lyse _Escherichia coli_, _Salmonella typhimurium_, _Listeria monocytogenes_, and _Staphylococcus aureus_ cells suggested that cell wall destruction is not their principal mechanism of action. Treatment-induced release of autolytic enzymes from the membrane-bound cell wall eventually induces lysis [31], which may explain the delayed lysis of _Escherichia coli_, _Salmonella typhimurium_, _Listeria monocytogenes_, and _Staphylococcus aureus_ noticed when suspensions were re-examined after several hours.