Features of colonization of the phytosphere of wheat seedlings by introduced strains of Escherichia coli

The paper presents the results of the study of the ability of introduced Escherichia coli strains to colonize different niches of the phytosphere – the rhizosphere, endosphere, and phylosphere of Mersia winter soft wheat seedlings and to influence the plant growth response under these conditions. The ATCC 8739 and clinical E. coli strains were used as the study material, as well as an isolate from the wheat agrocenosis soil. The vegetation experiments were carried out in the factorial chamber of the Department of Plant Physiology and Biochemistry of Plants and Microorganisms of V.N.Karazin Kharkiv National University. The experimental plants were inoculated with suspensions of E. coli strains and soil isolate by watering them in vegetation vessels where seedlings were grown for 10 days. In parallel by the method of successive washes, we analyzed the dynamics of the number of E. coli CFU in the rhizome, endo- and phyllosphere of seedlings. After completion of the experiment, the growth response was analyzed by linear growth and by the integral index of growth and biosynthetic processes – biomass accumulation. The results of experiments show that inoculation with ATCC 8739 and clinical strains of E. coli reduced the germination of wheat seeds and inhibited the growth response. Inoculation with E. coli soil isolate has virtually no effect on seed germination, linear growth, and biomass accumulation by Mersia seedlings. It was found that the number of E. coli bacteria in the phytosphere of wheat plants depended on the type of inoculated strain and differs in different parts of the seedlings phytosphere. The maximum number of E. coli CFU in the phytosphere was detected at the inoculation of plants with the clinical strain, three times less – at exposure to the soil isolate, almost 6 times less – at the inoculation with the standard strain. Differences in the degree of colonization of different parts of the phytosphere were detected at the inoculation of the test seedlings with different strains and soil isolates of E. coli: in the control variant and under the influence of ATCC 8739, the distribution between the rhizo- and endosphere is approximately the same. When the plants were inoculated with the clinical strain, endosphere was colonized, when using the soil isolate – the rhizosphere. In the phyllosphere of the experimental seedlings, only cells of the clinical strain were found in a small number, which indicates its increased adhesive properties. Plant-microbial relationships and the ability of conditionally pathogenic E. coli bacteria to colonize different areas of the plant organism and to use wheat seedlings as an alternative host are discussed.