The present study investigated the influence of different nanomaterials on physiological and biochemical activity of the nitrogen-fixing bacteria Azotobacter vinelandii IMV V-7076 and phosphate mobilizing bacteria Bacillus subtilis IMV V-7023 for the development of high-efficient free-flowing bacterial complex for crop production. Among the studied nanomaterials, vermiculite stimulated the most effectively bacterial growth, synthesis of amino acids and phytohormones, dehydrogenase, catalase and peroxidase activities. Based on vermiculite and highly efficient strains of bacteria Azotobacter vinelandii IMV V-7076 and Bacillus subtilis IMV V-7023, a free-flowing bacterial complex preparation for crop production was created. The preparation was stable during storage, it improved the nitrogenous and phosphorus nutrition of plants stimulated their growth by biologically active substances and protected plants from lesion by phytopathogenic micromicetes and bacteria.
Bacteria of the genus Bacillus are known for their ability to mineralize organic phosphorus compounds. Phytates constitute up to 60–80% of the total plant phosphorus and almost 50% of soil organic phosphorus. Phytates phosphorus is unavailable for plants. Bacillus can synthesize phosphatases both wide spectrum of action, and highly specific phytases that catalyze the hydrolysis of phytates. Therefore, the aim of this work was to study the growth and phytase activity of Bacillus subtilis IMV B-7023, which is the component of the ”Azogran” complex bacterial preparation for plant growing. Methods. The growth activity of bacteria was studied by cultivation methods, the phytase activity – by measuring the amount of phosphate released from sodium phytate during the enzymatic reaction. Results. It was shown that B. subtilis IMV B-7023 assimilated phytate as the source of phosphorus nutrition during cultivation in media with 0.5, 1.0 and 2.0 g/L of sodium phytate. The highest growth activity of these bacteria was observed after two days of cultivation in medium with 1.0 g/L of phytate. The number of bacteria was (3.91±0.32)×109 CFU/mL under these conditions. At the same time, B. subtilis IMV B-7023 demonstrated a low level of phytate assimilation as a source of carbon nutrition. Thus, after two days of cultivation the number of bacteria increased from (4.12±0.09)×106 CFU/mL to (1.07±0.07–3.11±0.51)×107 CFU/mL in the presence of 0.5–2.0 g/L phytate in the medium and the absence of another carbon source. It was determined that strain B. subtilis IMV B-7023 had phytase activity, the highest activity (221.85±0.12 U/g) was on the first day of their cultivation in medium with inorganic phosphates. It should be noted that B. subtilis IMV B-7023 phytase activity was lower during cultivating in medium with sodium phytate as a source of phosphorus nutrition, than in medium with inorganic phosphates. The obtained fact may be due to phytate hydrolysis by widespecific phosphatases. Higher rates of phytase activity obtained on the first and third days compared to the second and fourth days of bacterial cultivation may indicate the expression of phosphatases genes only in the period required for maximum bacterial development, in the absence of these proteins in the media. At the same time, the phytase activity of B. subtilis IMV B-7023 after 2 days cultivation in a media with 0.5 and 1.0 g/L of sodium phytate (194.80±0.15 U/g and 160.90±0.13 U/g, respectively) as the source of carbon and phosphorus was higher compared to the activity of bacteria on medium with inorganic phosphates (137.79±0.10 U/g). This may be caused by the synthesis of a larger number of highly specific phosphatases (phytases) in bacterial cells at the presence of only phytate in the medium as a substrate. Conclusions. B. subtilis IMV B-7023 strain is characterized by growth on nutrient medium with sodium phytate and phytase activity. Because they are soil microorganisms used as the component of the ”Azogran” complex bacterial preparation for plant growing, the ability to hydrolyze and assimilate phytate is important for functioning of this strain in the rhizosphere. The obtained results extend the understanding of B. subtilis IMV B-7023 influence on phosphorus nutrition and development of plants.
Bacteria of the genus Azotobacter are known for their ability to stimulate plant growth and development. Azotobacter vinelandii IMV B-7076 strain was isolated from Zhytomyr region soil of Ukraine. It is one of the components of the "Azogran" complex bacterial preparation for plant growing. It has been established that A. vinelandii IMV B-7076 synthesizes biologically active substances that promote plant development. At the same time, the antagonistic activity of A. vinelandii IMV B-7076 against phytopathogens has not yet been studied, so this became the aim of this work. Methods. The antagonistic activity of A. vinelandii IMV B-7076 was determined by agar well diffusion and agar blocks methods. Results. It was shown that A. vinelandii IMV B-7076 had antagonistic activity against some phytopathogenic fungi. In particular, the diameter of growth inhibition zones of Alternaria alternata 16861, Fusarium avenaceum 50720, Fusarium verticillioides 50463, Fusarium lactis 50719, Fusarium oxysporum 54201, Fusarium poae 50704 was 14-37 mm, Bipolaris sorokiniana 16868 and Fusarium solani – 11-13 mm. Fusarium culmorum 50716 and Fusarium graminearum 50662 were not sensitive to A. vinelandii IMV B-7076 metabolites. Notably, the antagonistic effect was demonstrated in mycelial growth and spore formation inhibition, in fungal mycelium discoloration. It was also demonstrated that A. vinelandii IMV B-7076 did not show antagonistic activity against phytopathogenic bacteria Agrobacterium tumefaciens 8628, Pectobacterium carotovorum subsp. carotovorum 8982, Pseudomonas fluorescens 8573, Pseudomonas syringae pv. syringae 8511, Clavibacter michiganensis subsp. michiganensis 13a, Xanthomonas campestris pv. campestris 8003b. Conclusions. Studied A. vinelandii IMV B-7076 strain is characterized by antagonistic activity against phytopathogenic fungi and does not have antibacterial properties against phytopathogenic bacteria. The antifungal activity of A. vinelandii IMV B-7076, as a component of "Azogran", will be useful for this bacterial preparation application in plant growing.
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