Changes in the physicochemical and cultural properties of the bacteria Azospirillum baldaniorum Sp245 under the influence of some synthetic coumarins

Due to the small number of studies on the role of coumarins in associative symbiotic relationships, some aspects of the influence of synthetic coumarins on the physicochemical and cultural properties of Azospirillum baldaniorum Sp245 were studied for the first time. To reveal the role of hydroxylation in position 7 of the fused aromatic ring – 1-(2-oxo-2H-chromen-3-yl)butan-1,3-dione, comparative studies of the effect of the original and hydroxylated coumarins on the culture of a model strain of azospirilla were carried out. The survival of bacteria after the addition of coumarins was studied by counting CFU on an agar medium. The biofilm formation activity of the culture was assessed using crystal violet. The change in the surface of bacteria under the action of coumarins was studied by the electrical polarizability of bacterial cells on an ELUS electrooptical analyzer (EloSystemGbR, Germany). The yield and monosaccharide composition of extracellular glycopolymers were studied using gas-liquid chromatography.For the first time, an increase in the yield of EPS of bacteria during growth in the presence of 1-(7-hydroxy-2-oxo-2Hchromen-3-yl)butan-1,3-dione by 1.2 and 1.7 times for concentrations of 50 and 100 μM respectively was observed. It has been established for the first time that the hydroxylated substance has a higher antibacterial activity compared to the unsubstituted one. A decrease in the number of viable cells in planktonic culture and inhibition of biofilm growth were revealed. It has been shown by electro-optical analysis that the presence of coumarins in the cultivation medium in all concentrations studied leads to a change in the electrical polarizability of A. baldaniorum Sp245 cells. The use of electrooptical analysis of cell suspensions using monospecific antibodies obtained against lipopolysaccharides of this strain made it possible to reveal the absence of changes in carbohydrate antigenic determinants on the surface of bacterial cells. This is consistent with the data of the analysis of the composition of extracellular polysaccharides by GLC, during which no differences were found in the qualitative composition and ratio of monosaccharides. An increase in the yield of bacterial EPS during growth in the presence of 1-(7-hydroxy-2-oxo-2H-chromen-3-yl) butan-1,3-dione by 1.2 and 1.7 times for concentrations of 50 and 100 μM was shown. The results obtained allow us to consider the changes that have occurred as features of the adaptation of bacteria to the associative conditions of existence.