3.5. Antibacterial Activity Measurements

The antimicrobial properties of compounds were determined against selected bacteria: Micrococcus luteus, Bacillus subtilis, Escherichia coli and Pseudomonas fluorescens which came from the collection of Pure Cultures of the Facility of Microbiology of the Department of Soil Science and Microbiology of the Poznan University of Life Sciences.

The well-diffusion method was used to evaluate the antimicrobial properties of compounds. 6 mL each of liquidized broth medium was poured into sterile Petri dishes and allowed to solidify. After which, two sterile glass rings with a diameter of 0.5 cm were placed on the surface of each plate. Then 20 mL each of liquid broth medium containing suspensions of the tested bacterial strains at a density of 10⁷ cells/cm3, obtained from 48-h cultures on broth slants, was introduced. After the medium solidified, the glass rings were removed with a pencil, obtaining two wells on each plate. 0.1 mL of compound dissolved in pure dimethyl sulphoxide was introduced into one well, and 0.1 mL of pure dimethyl sulphoxide was introduced into the other well, which was as a control. Each compound was tested in four replicates. The plates were incubated for 48 h in a thermostat at 27 °C for M. luteus, B. subtilis and P. fluorescens cultures, and the E. coli culture at 37 °C. At the end of the incubation, the diameters of growth inhibition of the tested strains were measured using calipers.