## 1 Introduction  
Herbal preparations, including those using plant extracts of echinacea (_Echinacea purprea_) and rue (_Ruta gravelens_), are widely known and increasingly used due to their significant healing properties, although little is known about their mode of action [1, 2]. _E. purprea_ is a perennial plant native to eastern North America that belongs to the _Asteraceae_ family. The plant is widely known for its medicinal properties, being one of the most used medicinal plants for its immunositulant properties. This plant species is considered a safe herbal medicine, thus, it is usually used through extracts of the dried aerial parts or roots. The most common phytochemicals in _E. purprea_ are alkalamides, polysaccharides, lipoproteins, betaine, sesquiterpenes, polyacetylene, saponins and phenolic compounds, responsible for its biological properties [2]. In turn, _R. gravelens_ is widely distributed in various geographical regions of Afro-Asian countries. This plant is cultivated as a decorative plant and is used in traditional medicine for treating many disorders. All parts of the plant contain the active compound, but they are mostly found in leaves [1]. _R. gravelens_ represents plants of the _Rutaceae_ family, which are a big repository of secondary metabolites responsible for their aroma (terpenes), pigmentation (quinones and tannins) and flavour (terpenes). The extracts of these plants are a mixture of various compounds, such as terpenoids and phenols, to which antiseptic, antifungal, antioxidant and antitumoral properties are attributed [3, 4]. Particular importance is attached to such botanical extracts in relation to their antimicrobial effects against certain pathogenic bacteria, where it is uncertain whether they have any other effects on select groups of microorganisms [5; 6; 7]. It is worth knowing the effects of such mechanisms of action, as combinations of naturally antimicrobial plant extracts with other active agents of similar effectiveness may be more effective than those used as individual therapies [7]. Antimicrobial agents that can potentially be combined with plant extracts to create more effective preparations include bacteriophages (phages), which are currently getting more popular. Phages are viruses specific to bacterial cells known for over hundred years, which can successfully supplement or even (in some cases) replace traditional methods of prevention and treatment of bacterial diseases, especially those caused by strains which are found to be resistant to routinely used antimicrobial drugs [8]. The biochemical complexity of the molecules that make up the phage virion, their diversified size (expressed in the nanometric scale), the electric charge and hydrophobicity make bacteriophages interact with other materials in various ways. Those include different types of interactions with stimulating or antimicrobial effects, e.g., by altering phage activity as a result of a synergistic or antagonistic effect [9; 10]. It should also be remembered that inhibition of bacteriophage proliferation or \"antiphage activity test\" is a sensitive, rapid and low-cost presceening test, which can be applied to reliably detect pharmacological activity [11]. Moreover, bacteriophages have significant advantages, such as easy handling and cultivating in standard laboratory media. Therefore the employment of phages is being also propose to serve as eukaryotic cell virus surrogates [12; 13; 14].  
Therefore, in the current study, interplays between lytic bacteriophages and plant extracts of echinacea (_Echinaca purpurea_) and rue (_Ruta gravelens_) have been investigated for their possible interactions in the bacterial environment, including possible antagonistic effects. To the best of our knowledge, this is the first work describing such phenomena.