THE EFFECT OF CATECHIN, TANNIC AND GALLIC ACIDS ON BIOFILM FORMATION IN Escherichia coli DEPENDS ON THE MEDIUM COMPOSITION

Catechin, tannic and gallic acids belong to the most abundant nutritional plant polyphenols capable of modulating physiology of gut bacteria. The described modulation patterns vary from prebiotic/protective to anti-biofilm/antibacterial. Adequate interpretation of observed effects requires investigation of contributing factors. Apparently, applied dose and composition of the cultivation medium might be both essential for switching between planktonic and biofilm lifestyles. The aim of the present study was to study the effects of broad concentration range of catechin, tannic and gallic acids on pharmacodynamical parameters and biofilm formation in Escherichia coli BW25113 in minimal media M9 supplemented with glucose and LB broth. Here we showed the distinct modes of mass biofilm formation (BF) in Escherichia coli BW25113 in LB broth and M9 supplemented with glucose in the presence of polyphenols. BF was inhibited by 4 mg/ml catechin, tannic and gallic acids in LB, while in M9 tannic acid induced BF which correlated with no minimal biofilm prevention concentration (MBPC) found for tannic acid, while for gallic acid MBPC was 4 mg/ml. In both media minimal inhibitory concentrations (MICs) for tannic and gallic acids were 1 and 4 mg/ml, respectively, while minimal bactericidal concentration (MBC) was only found for gallic acid (4 mg/ml) in LB broth. In certain cases, the amount of cells undergoing biofilm formation was altered. Calculation of specific biofilm formation revealed absence of inhibiting effects for gallic acid, however stimulation by tannic acid was still present in both media.