Effect of Probiotic Microorganisms on Catalase Activity, Fractional Composition of Soluble Proteins, and Intestinal Microbiota of Honey Bee

Recently, there has been a trend toward the use of new effective natural preparations to fight diseases and improve the health of honey bees. It is also known that a well-balanced structure of the intestinal microbiota of honey bees is the basis for their growth, development, strengthening of the immune response, and resistance to infections. It has been established that some strains of lactic acid bacteria that have antibacterial, anti-inflammatory, and immunomodulatory properties, are promising for the development of broad-spectrum probiotic preparations based on them. Therefore, the aim of the work was to determine the effect of probiotic strains Lactobacillus сasei IMV B-7280 and L. plantarum IMV B-7679 on catalase activity, protein content and protein profile of hemolymph, as well as microbiota spectrum of different parts of the intestines of Apis mellifera honey bees. Methods. To conduct the research, a control and two experimental groups of 60-90 bees each were formed. The bees of the control group were fed 60% sugar syrup + 1 mL of distilled H2O for 28 days. The experimental group of bees D1 received 1 mL of 60% sugar syrup + 1 mL of aqueous suspension containing cells of the L. casei IMV B-7280 strain at a concentration of 1 ∙ 106 CFU/mL every day; experimental group of bees D2, in addition to 1 mL of 60% sugar syrup, received 1 mL of aqueous suspension containing cells of L. plantarum IMV B-7976 strain at a concentration of 1 ∙ 104 CFU/mL. Catalase activity of the whole organism tissues was determined using the ability of hydrogen peroxide to form a stable colored complex with molybdenum salts on a spectrophotometer at a wavelength of 410 nm against water. The amount of protein in the whole organism tissues was determined by the Lowry method. The content of total protein in the body of bees was carried out according to the Kjeldahl method. Determination of the content of individual fractions of soluble proteins of the hemolymph was carried out by the method of vertical electrophoresis in a 7.5% polyacrylamide gel. The relative content of protein fractions was determined using the TotalLab TL120 program and expressed as a percentage of the total pool. To determine the qualitative and quantitative spectrum of the gut microbiota of bees, the hindgut and midgut were sampled (separately) from bees of control and experimental groups. The obtained samples were plated on eight selective solid media for cultivation of different groups of microorganisms. Results. A tendency to increase the catalase activity of bee tissues after 28 days of L. casei IMV B-7280 strain use and a consistently higher activity of this enzyme throughout the experimental period under the action of L. plantarum IMV B-7679 strain was established. In the control group of 28th days, the content of bees and catalase activity remained at a constant level. It was shown that on the 14th day and total protein in the body of bees that received L. casei IMV B-7280 strain increased signifi cantly. Water-soluble fractions of hemolymph proteins were found in bees of both groups: γ-globulins, β-globulins, α2-globulins, and α1-globulins. It should be noted that the albumin fraction was not detected. It has been shown that the hindgut contains a much larger number of microorganisms than the midgut. The use of L. casei IMV B-7280 strain led to an increase in the number of lactic acid bacteria and bifidobacteria in both parts of the gut, as well as to a decrease in the number of staphylococci, streptococci, and microscopic fungi. The use of L. plantarum IMV B-7679 strain had a similar effect, but the changes in the composition of gut microbiome were less pronounced. Conclusions. The use of probiotic strains L. casei IMV B-7280 and L. plantarum IMV B-7679 for feeding bees under the conditions of a laboratory thermostat led to quantitative changes in the composition of the intestinal microbiota of bees, namely an increase in the number of lactic acid bacteria and bifidobacteria, as well as a decrease in the number of some other groups of microorganisms in the gut. Probiotic strains stimulated catalase activity of bee’s body tissues, increased the level of total protein, and did not significantly affect the ratio of hemolymph protein fractions.