Among 18 plant extracts studied black tea, A. uva ursi, V. vitis-idaea, T. сordata, B. pendula and Z. mays stimulated biofilm formation, while the extracts of A. millefolium, U. dioica and L. japonica demonstrated inhibiting effects. Some of the extracts also inhibited rpoS expression both in biofilms and planktonic cultures. To elucidate the role of RpoS sigma-S factor in the observed effects of the plant extracts, we studied influence of different doses of pure plant polyphenol quercetin on biofilm formation in strains with different levels of RpoS. It was found that negative influence on biofilm formation was due to the RpoS excess. Collectively, our data indicate the possibility of RpoS-independent pathway of biofilm formation regulation in the pres-ence of plant extracts containing polyphenols.Исследование выполнено при поддержке грантом РФФИ-Урал № 14-04-96031, грантом №12-И-4-2072 по Программе интеграционных проектов Президиума УрО РАН, а также грантом Президиума УрО РАН для молодых ученых 14-4-НП-126
