PLANT GROWTH-PROMOTING PROPERTIES OF HEAVY METAL RESISTANT BACTERIA ISOLATED FROM THE RHIZOSPHERE OF COLOBANTHUS QUITENSIS (KUNTH) BARTL. (DESEPTION ISLAND, MARITIME ANTARCTICA)

Considering climate change and soil pollution caused by human activity, including hostilities, the isolation of plant growth-promoting microorganisms resistant to environmental factors is a current issue. Environments with extreme conditions are a source for the isolation of microorganisms that may have potential for use in biotechnology. Aim of the study: to study the ability of metal-resistant halotolerant bacterial isolates from the rhizosphere of C. quitensis (Kunth) Bartl. (Deception Island, Maritime Antarctic) to synthesize siderophores and auxinlike compounds, fix molecular nitrogen, solubilize zinc compounds, synthesize certain enzymes, and stimulate the growth of spring wheat Triticum aestivum of the Tybalt variety, as well as to select promising strains for identification and inclusion in microbial preparations. Materials and methods. Bacterial isolates were purified, and their properties were studied using classical microbiological methods. The ability to produce siderophores was detected using chromazurol S and hexadecyltrimethylammonium bromide, while auxin-like compounds were detected using Salkovsky's reagent. Wheat seeds were inoculated with bacterial suspensions and sown into the soil. Seed germination, moisture content, dry weight, pigment content in leaves, and morphometric parameters of seedlings were studied. Results. Six of the 19 selected halotolerant metal-resistant bacterial isolates that produced siderophores, auxin-like compounds, and enzymatic activity (D388 and D391 – amylase, D389 and D394 – protease, D390 – lipase, D395 – protease, amylase, lipase, lecithinase, cellulase) were chosen for study of their effect on wheat growth. The total chlorophyll content was the highest in wheat leaves treated with isolates D389 and D388. The chlorophyll a content in wheat leaves treated with isolates D389, D395, and D388 was 13.4–28.7% higher than in the control. The highest content of siderophores was found in the culture medium of isolate D388 (10.94±1.2 conventional units), and auxin-like compounds (10.93±1.0 μg/ml) – in isolate D387. Conclusions. Metal-resistant halotolerant isolates of bacteria from the rhizosphere of C. quitensis have a growth-promoting effect on wheat. Based on their ability to synthesize siderophores, auxin-like compounds, fix N2, solubilize ZnO, have amylase activity, and stimulate the growth of T. aestivum, isolate D388 was selected for identification and testing as part of a bacterial preparation.