BOOK OF ABSTRACTS 223 IHSS&IWA26 / BRNO / CZECHIA / 23–28 August 2026 Hall A Poster Session / Environment, Agriculture, and Forestry P4.6 Effects of Bacterial Inoculants on Soil Microbial Characteristics Barbora Hlaváčková1, Martin Súkeník1, Petr Haleš1, Michal Kalina1, Petr Sedláček1 1 Brno University of Technology, Faculty of Chemistry, Purkyňova 464/118, 612 00, Brno, Czech Republic, 236863@vutbr.cz Plant-growth-promoting rhizobacteria (PGPR) belongs to a group of soil bacteria that can influence plant growth through various mechanisms. In recent years, there has been an increase in the use of various types of soil conditioners containing PGPR in the form of bioinoculants. The main aim of these approaches is to increase yields and improve crop growth under adverse conditions in an environmentally friendly manner. Encapsulating microorganisms in a hydrogel form of suitable polymeric carrier offers not only easier sample handling (compared to liquid formulations) but also a range of other benefits. Microorganisms are better protected against stress factors (changes in conditions, osmotic stress), and the gradual degradation of the polymer matrix allows their controlled release. All these aspects increase survival ratio of bacteria and thereby enhances their effectivity in subsequent soil applications [1]. The aim of this study was to quantify the effects of externally applied soil carriers containing PGPR on the growth of the model plant – common garde lettuce (Lactuca sativa) under adverse conditions (drought). The rhizobacterium strain Azotobacter vinelandii CCM 289 was selected for preparation of four different application forms: bacterial biomass in PBS, alginate gel without culture, gel with bacterial culture and lyophilized gel with bacterial culture. The effect of each treatment was compared to a negative control without any addition (white). In the cultivation experiment, artificial soil with a low organic matter content (4 wt.%) was used to simulate poor soil during a drought. During the cultivation experiment, the physicochemical characteristics of the soil (temperature, moisture, pH) and the growth characteristics of the lettuce (number of leaves, height, and width of the aboveground parts) were monitored. After the cultivation experiment was completed, the effect of these used treatments on the physical and chemical characteristics of the soil and on plant growth (number of leaves, length, fresh weight, and dry weight) was analyzed, along with an analysis of the root system. Furthermore, the concentration and viability of microorganisms in the soil were determined, as well as the effect of addition of different used soil treatments on the microbial activity of the soil microbiome, using cultivation on
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