Effect of acrylate-based hydrogels on basic cultivation parameters and antagonistic activity of soil beneficial bacteria

We study the effect of polymeric acrylate-based hydrogels on the growth and development of soil beneficial microflora, including nitrogen-fixing and phosphate-mobilizing microorganisms, entomopathogens and phytopathogen antagonists. The antibacterial effect of hydrogels (HG) was studied by the volume displacement method in Petri dishes according to Ye. Sagi. Bacteria were cultured in GRM broth; the optical density of the medium was determined at 600 nm at 1 h intervals for 48 h. The process of biofilm formation was studied in LB medium according to the method of O'Toole and Kolter (1998). HG samples were added to sterile medium at concentrations of 200, 100, 50, 25 and 12.5 mg/ml. The Paenibacillus polymyxa P and Agrobacterium tumefacience 204 strains, as well as the Bacillus thuringiensis 0271 and B. thuringiensis 0371 entomopathogens, showed no signs of inhibition in the interaction zone with both control and experimental HG. At the same time, the culture growth of the Azotobacter vinelandii 10702, Bradyrhizobium ottawaense M-8 and Rhizobium leguminosarum K-29 strains was inhibited in all the experiment variants. The investigated hydrogel suspensions HG1 and HG2 at a concentration of 200 mg/ml contributed to a decrease in the optical density of cultures of both B. amyloliquefaciens 01-1 and Lelliottia nimipressurales 32-3 by on average 23.3 and 14.7%, respectively, compared to the control. Introduction of HG2 into a nutrient medium in the amount of 25-100 mg/ml promoted active accumulation of biomass by P. polymyxa P and A. tumefacience 204. The HG1 and HG2 hydrogels at concentrations of 50-200 mg/ml and 100-200 mg/ml, respectively, enhanced the biofilm formation of B. amyloliquefaciens 01-1. The maximum stimulation of plankton culture and biofilm formation was observed when the P. polymyxa P strain culture was enriched with 12.5-100 mg/ml of HG1, which increased the intensity of bacterial suspension growth by on average 8.9 times compared to the control.

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