Combinations of Echinacea (Echinacea purpurea) and Rue (Ruta gravolens) Plant Extracts with Lytic Phages: A Study on Interactions

Abstract

The use of combined biocontrol strategies to combat bacterial-related issues is an increasingly popular approach. Therefore, a novel investigation was performed, where interactions of lytic bacteriophages (MS2, T4 and phi6) and methanolic plant extracts (Echinacea purpurea (EP) and Ruta graveolens (RG)) in the bacterial environment have been examined to understand their application potential and limitations. Due to the complexity of these interactions, many up-to-date techniques were used (microdilution method, phage extract coincubation assay, static interactions synographies and dynamic growth profile experiments in a bioreactor). As a result of our study, antagonism interactions were observed: EP and RG extracts showed antiphage and bacterial stimulating activity. Effects caused by low extract concentrations on microorganisms depended on the species of phage and bacteria, while high concentrations suppressed bacterial lysis in general. Moreover, interactions observed in the static environment differed from those performed in a dynamic environment, showing the importance of performing multiple analyses when investigating such complex mixtures.