Growth and Phytase Activities of Bacillus subtilis IMV B-7023 During Cultivation with Sodium Phytate

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.

Damage to sugar beets by cercosporosis and gray rot, depending on the characteristics of fertilization

The results of field and laboratory research on podzolized heavy loam chernozem of the Right-Bank Forest-Steppe of Ukraine to study the effect of various fertilization systems on the infestation of sugar beet by cercosporosis and gray rot are presented. It has been found that changes in nitrogen, phosphorus and potassium nutrition have a different effect on the development of diseases. The semi-rotted cattle manure on straw bedding and mineral fertilizers in the form of aqueous ammonia, ammonium nitrate, granular superphosphate, mixed potassium salt, potassium chloride, ammonium nitrate phosphate fertilizer grade A and liquid complex fertilizers of grade 10–34–0 were used in the experiment. The rate of manure is 40 t/ha, the rate of mineral fertilizers – N120Р120К120. Fertilizers were applied in August during fall plowing, as well as in late autumn at the end of October, together with the soil subsurface loosening to a depth of 14–16 cm, and in spring – for presowing cultivation. The degree of the leaf apparatus damage by cercosporosis and the intensity of the disease development were determined. The resistance of root crops to gray rot was determined by a microbiological method. For this, cuttings from root crops were placed in Petri dishes with a provocative background of a pure culture of the fungus Botritis cinerea Pers. The conducted studies have established that, depending on the types, forms and timing of mineral fertilizers against the background of manure, the degree of the leaf apparatus infestation of beets with sugar cercosporosis varies from 24 to 48 % and increases both for insufficient and unbalanced phosphorus nutrition. At the same time, the improvement of nitrogen nutrition, especially with the late autumn application of aqueous ammonia, compared with its introduction for the August plowing, contributes to an increase in the degree of stability of the leaf apparatus of sugar beet to cercosporosis from 46.6 to 60.0 %. Improving the mineral nutrition of plants through the use of fertilizers helps to increase the resistance of root crops to decay. At the same time, depending on the fertilizer application system, the degree of stability compared to the control without fertilizers increases by 8.5–38.9 %. This was especially effectively promoted by the improvement of phosphorus nutrition of plants. A high correlation dependence was established between the damage of leaf apparatus of sugar beet by cercosporosis and the formation of a rotten mass of root crops (r = 0.85).