Organizing co mmittee

THE USE OF NATURAL SUBSTANCES OF PLANT ORIGIN FOR 
THE PRODUCTION OF PROMISING ANTIBACTERIAL DRUGS 
Pavel A. Nazarov, Marina V. Karakozova 
Belozersky Institute of Physico-Chemical Biology, Lomonosov Moscow State 
University, Moscow, Russia 
Antibiotic resistance is a global problem of modern medicine. Multidrug resistance 
(MDR) pumps, involved in the formation of resistance to xenobiotics, the export of 
toxins, the maintenance of cellular homeostasis, and the formation of biofilms and 
persistent cells, are the keystone of bacterial protection against antibiotics. MDR pumps 
are the basis for the nonspecific protection of bacteria. Thus, the nonspecific protection 
of bacteria formed by MDR pumps is a barrier that prevents the penetration of 
antibacterial substances into the cell, which is the main factor determining the resistance 
of bacteria. Plant extracts are promising sources of new antimicrobials. The key aspect 
is the penetration of antibacterial substances of plant origin into the bacterial cell 
through the protective barrier from the MDR pumps.
In this paper, we investigate the role of MDR pumps in protecting bacteria from 
antibiotics containing components of plant origin in order to elucidate the principles of 
selection of such compounds by MDR pumps. We tested various compounds such as 
berberine, plastoquinone, palmatine, carvone and limonene for gram-positive and gram-
negative bacteria. We also used well-known antibiotics and antibacterial agents, such as 
chloramphenicol, triphenylphosphonium derivatives, rhodamine derivatives. We 
analyzed various deletion mutants for MDR pumps and established the role of pumps in 
biofilm formation and, at the expense of pumps, in protecting bacteria from antibiotics 
and herbal substances. 
We compared the antimicrobial action of antibiotics and herbal substances Gram-
negative bacteria E. coli by using standard 2-fold broth microdilution assays in identical 
conditions. We used various sub-lethal concentrations and incubation times with 
antibiotics and herbal substances to determine which pumps are influencing biofilm 
formation. To assess how compounds affect biofilm formation we evaluated the effects 
of a substances on biofilm formation as a change in the ratio of planktonic and sessile 
forms of bacteria by means crystal violet staining. To determine the number of 
surviving cells in the biofilm, we determined the CFU for each mutant by the MDR 
pump, which differed from the wild type in activity. 
The originally floating form of the bacteria has evolved into a fully sessile biofilm 
form under pressure of some herbal substances. Moreover, in the form of a biofilm, a 
slow growth of bacteria was observed, which confirmed our assumption about the 
survival of bacteria due to the growth of the bacterial population in the composition of 
the biofilm. It is interesting that a number of substances were not recognized by MDR 
pumps, which suggests the presence of plant molecules "invisible" to bacteria that could 
be used in antibiotic therapy. 
This research was funded by Russian Science Foundation (RSF) grant 22-15-00099.