Properties of bacteria isolated from Antarctic vascular plant Colobanthus quitensis and their plant growth-promoting potential

Abstract

Background. The study of bacteria inhabiting the endosphere of Antarctic plants is relevant because it complements data on the role of microorganisms in improving plant growth and their resistance in extreme environments. The targeted use of endophytic bacteria as biofertilizers in agriculture is a promising technology for providing effective, environmentally friendly solutions, especially amid climate change. The study aimed to investigate the properties of bacteria isolated from Colobanthus quitensis and to determine their effects on the growth parameters of the spring wheat cultivar Tуbalt in the early stages of ontogenesis and select a strain with plant growth-promoting traits for further research. Materials and Methods. Endophytes were isolated on TSA and R2A. The ability of bacteria to fix N2 was determined using Ashby medium. Conclusions about zinc solubilization were made based on the appearance of transparent zones around colonies after growth on medium containing ZnO. For the detection of cellulase activity, a medium with carboxymethylcellulose was used, and for amylolytic activity – starch-ammonia agar. The ability of bacteria to synthesize siderophores was determined using a medium containing hexadecyltrimethylammonium bromide and chromazurol S. The content of auxin-like compounds was determined using Salkowski reagent. The seeds were soaked in a bacterial suspension, sown into soil, and grown for 8 days at 18 ± 2 °C. Protein concentration was determined using the Bradford method. Chlorophyll a and b concentrations were determined photometrically. To assess the effect of heavy metal salts and NaCl, different amounts of these substances were added to the medium. Results. Some bacterial isolates obtained from the endosphere of C. quitensis solubilize ZnO and produce cellulases and amylases. All bacterial isolates studied produce auxin-like compounds, and most of them synthesize siderophores. Moderate and extreme halophiles are capable of growing under the influence of MnCl2 · H2O, FeSО4 · 7Н2O, CdCl2 · 2.5H2O, CoCl2 · 6H2O, and K2Cr2O7. Most of the bacterial isolates obtained from the endosphere of C. quitensis, despite possessing plant growth-promoting traits, had no effect on wheat growth parameters during the early stages of ontogenesis. However, bacterial isolates have also been detected that positively affect morphometric parameters and chlorophyll content in seedling leaves. Bacterial isolate R380 from the endosphere of C. quitensis roots, which increased chlorophyll content in the leaves of wheat after seed inoculation, was identified as Bacillus sp. R380 based on 16S rRNA gene sequencing. Conclusions. As a result of screening Colobanthus quitensis endophytes, we isolated a promising strain, Bacillus sp. R380, which increases chlorophyll content in spring wheat seedlings.