## 4 Discussion
However, there are some findings describing more complex interactions. One shows the influence of a crude acetone extract of the pit of date palm (_Phoenix dactylifera_L.) on the lytic _Pseudomonas_ phage ATCC 14209-B1 by changes in the absorbance. It was found that the extract showed the ability to inhibit the infectivity of the phage and completely prevent bacterial lysis. Similarly to our work, authors observed that the higher the concentration, the bigger the phage inhibition [45]. However, a limited number of extract concentrations were used, and no information of the extract influence on bacteria alone was present. In another work, aqueous extract of _E. ammonium_ dried flower was used, and the antiviral activity against _S. aureus_ bacteriophage 3C was determined by the agar overlay method and one-step growth experiment. Antibacterial activity was determined by the agar well diffusion and minimum inhibitory concentration methods. The extract also showed concentration-dependent antiviral activity and reduced the yield of phage [46]. However, since a subinhibitory concentration of the extract was used in the extract-bacteria-phage tests, the observed effects could also be due to the influence of the extract on bacterial cells to some extent. The importance of performing multiple tests in order to understand such complex interactions (that can change in different environments) was noticed in the study of other authors. The influence of phenolic compounds from pomegranate peels (Ps), grape seeds (GSs) and black cumin (NS) on _S. aureus_ phages was investigated by examining the effect of phenolic extracts on phage plaque sizes, and later calculating phage titers and bacterial counts from the mixed culture (phages-compounds-bacteria) experiment. It was found that only the NS extract had a positive effect on phage activity by increasing the phage plaque size; however, the same effect was not reflected in phage titers in a liquid medium. Overall, no synergistic effect was observed in liquid media experiments. Moreover, it was found that P and GS extracts inhibited phage activity, and the observed interactions were generally found to be more closely related to antagonism, similarly to what we found in our work [47]. Finally, comparably to some findings in our study, it was observed that plant extracts in combination with virulent phages can significantly reduce the bacterial concentration compared to untreated and extract-treated controls up to 6 h, but this reduction did not extend further (decreased over time). Moreover, in most cases, the phage and extract combinations did not significantly reduce the bacterial content compared to phages alone [7]. In our work, we also hypothesise that mixing itself can be responsible for some of the observed effects of the EP and RG plant extracts (by changing the environment conditions). It is worth noting that in our previous research, we also observed the stimulation of bacteria by plant extracts after introducing the mixtures into the dynamic (mixing) environment of a bioreactor [18]. This phenomenon can simply be explained by the enhanced physical contact of the extract molecules, bacterial cells and phages caused by mixing, which consequently enhances the interactions in the mixture that could not be observed in static conditions. However, a thorough understanding of this phenomenon may require further research.