###### Abstract
The antibacterial potential of polyphenols occurs at different levels, i.e., at the level of the bacteria cell (including damage of the bacterial membrane and inhibition of metabolism and toxin secretion, as well as a decrease in biofilm formation), the toxin level, and the host cell level [11]. Plant polyphenols can also act against _P. aeruginosa_. For example, betulin and betulinic acid have antiseptic activity, inhibit the formation of _P. aeruginosa_ biofilms, and quorum sensing controlled virulence factors [12]. [PERSON] described that catechin from _Combretum albiforum_ (Tul.) Jongkind (_Combretaceae_) bark extract reduced the biofilm activity of _P. aeruginosa_ by around 30% [13], while [PERSON] [14] noted that tea polyphenols induced morphological changes in _P. aeruginosa_ cells, as well as damaging the cell membrane of this pathogen. A very interesting sub-group of polyphenols with strong antibacterial activity is tannins. These secondary plant metabolites strongly interact with lipids, proteins, and polysaccharides, as well as possess antibacterial and antiviral activity [11; 15; 16]. [PERSON] described how tannic acid possesses broad antibacterial activity against such bacteria as _Staphylococcus aureus_, _Escherichia coli_, _Streptococcus pyogenes_, _Enterococcus faecalis_, _P. aeruginosa_, _Yersinia enterolitya_, _Bacillus cereus_, and _Listeria innocua_[17], whereas [PERSON] described how chestnut extract, as well as such pure tannins as vescalin, castalin, castalagin, vescalagin, and gallic acid, demonstrated antibacterial activity against _S. aureus_[18]. Also, we have previously demonstrated that tannins have strong antibacterial activity. For example, two hydrolysate tannins, i.e., 1,2,3,4,5-penta-\(O\)-galloyl-\(\beta\)-D-glucose (PGG) and 1,2,-di-O-galloyl-4,6-valoneoyl-\(\beta\)-D-glucose, inhibited the growth of _S. aureus_ (the 8325-4 strain). Additionally, PGG increased the antibacterial activity of such antibiotics as oxacillin, penicillin, and methicillin. Both tannins changed the lipid order parameter and decreased the rigidity of the bacterial membrane. Additionally, these compounds strongly interacted with _S. aureus_ membrane proteins and changed the size and chemical composition of staphylococcal membrane vesicles [19]. We have also demonstrated that PGG, 1,2-di-\(O\)-galloyl-4,6-valoneoyl-\(\beta\)-D-glucose, and 2-\(O\)-bis-digalloyl-4,6-valoneoyl-\(\beta\)-D-glucose have antibacterial potential for use against _Streptococcus mutans_ (_S. mutans_), responsible for the development of dental caries [16]. The antibacterial activity of tannins is connected not only with their bactericidal or bacteriostatic activity. PGG and 1,2-di-O-galloyl-4,6-valoneoyl-\(\beta\)-D-glucose inhibited \(\alpha\)-hemolysin channel formation as well as its conductivity. Also, PGG halted \(\alpha\)-hemolysin release/secretion from _S.aureus_, which can be connected both with PGG interaction with bacterial membranes as well as with the influence on _hla_ gene expression responsible for the biosynthesis of \(\alpha\)-hemolysin [20]. As we described above, this pathogen was placed by the WHO on the list of \"critical pathogens,\" and the development or discovery of new anti-pseudomonas compounds is very urgent. Due to the high and well-documented antibacterial activity of tannins, the main goal of our studies is to investigate and explain the molecular mechanisms of 3,6-bis-O-di-O-galloyl-1,2,4-tri-O-galloyl-\(\beta\)-D-glucose interaction, a tannin that is the main compound of _Rhus typhina_ L. (_R. typhina_) extract along with _P. aeruginosa_. Therefore the analyses at the bacteria protein and membrane level were carried out, and the biophysical and physicochemical parameters characterizing such interactions have been calculated.