## 4 Discussion
Moreover, the effect is also time-dependent, as it fades away with time, allowing for phage lysis afterwards. Our hypotheses of EP extract bacterial stimulating effects are in line with the results of other authors, where the activity of _E. purpurea_ against bacterial cells varied. The general antibacterial properties of _E. purpurea_ are detected mainly for their ethanol extracts [29]. Nevertheless, in the work, six different echinacea commercial ethanol extracts were analysed, including extracts from _E. purpurea_ roots and _E. purpurea_ aerial parts, and _E. coli_ was a species relatively insensitive to those extracts: no bacterial reducing effect was detected [6]. When the plant activity against Gram-negative bacteria was observed, hydroethanol extracts of the aerial parts of _E. purpurea_ were used, significantly _inhibiting E. coli_ growth [30]. At the same time, the work of other authors highlights that even in commercial hydroalcoholic echinacea extracts (roots of _Echinacea purpurea_ L. [PERSON]; roots, leaves, flowers and seeds of _E. purpurea_; aerial parts and roots of _E. purpurea_; and roots of _E. angustilgia_), obtained from certified trading houses, there is a difference in the extracts' properties [31]. That points out the differences of the plant activity against bacteria, that seems to be associated with the type of extraction and parts of the plant used in the experiments. As performed in our work, when the methanolic extract of _E. purpurea_ aerial parts was tested, there was no evidence of microbicide activity against _E. coli_, even at the highest tested concentration of 20 mg/mL [2] (highest tested concentration in our work: 25%, 37.4 g/L). Similar to our studies, in which the stimulating effect of EP was detected, it has been shown that echinacea supplementation (dietary supplement; aerial and root parts of the plant; patented extraction method) can stimulate bacteria, namely the selected groups of human gastrointestinal tract microbiota [5]. Moreover, studies have shown that _E. purpurea_ also possesses antiviral activity [21; 32; 33; 34] that could support our findings on the EP extract antiphage activity. The lysis profile experiments of the RG extract at the concentrations of 25% and 3.125% with the MS2 phage and _E. coli_ generally resulted in slightly increased biomass production compared to the control bacterial growth. At the coincubation test, RG 25% did not influence phage viability, whereas RG 3.125% caused a drop in MS2 counts. A modified microdilution assay in static conditions showed that RG 25% did not alter bacterial growth, whereas RG 3.125% stimulated _E. coli_. Therefore, the presented results concerning the higher extract concentration are a consequence of introducing mixing to the experimental environment, indicating that RG 25% could have become bacteria-stimulating and/or phage-inhibitory (as it was detected for RG 3.125%). That statement is additionally confirmed by the control curve of _E. coli_ + RG 25%, which is also characterized by a higher biomass production compared to the control _E. coli_ growth. The stimulating effect of the RG extract was also observed in the combination of _P. syringae_ and phage phi6, where RG 25% caused greatly enhanced bacterial proliferation. When RG 0.78% was used, phage lysis was present, but delayed by approximately 3 h. Coincubation assay revealed that both RG concentrations showed phagicidal activity, whereas a modified MIC test demonstrated a lack of their influence on bacteria. These interactions concerning RG 25% are again explained by both the phage-inhibitory and bacteria-stimulating (gained in the mixing environment) RG activity, since bacteria + extract control (_P. syringae_ + RG 25%) also showed pronounced bacteria-stimulating effect. The results observed for RG 0.78% are therefore the effect of reducing the stimulating influence of the extract by lowering its concentration and simultaneously abolishing the phagicidal activity of the extract in a dynamic environment. When mixtures of RG with T4 phage and _E.