Prikladnaâ biohimiâ i mikrobiologiâ

It has been shown that in the presence of the cells of five strains of Rhodococcus erythropolis, isolated from various anthropogenically polluted ecosystems, and an exogenous reducing agent (isopropanol), enantioselective reduction of ketones (acetophenone and 6-methyl-5-hepten-2-one) occurs with the formation of the corresponding S-configuration alcohols with high enantiomeric excess. Using the most active strain of R. erythropolis A-27 at the optimal concentration of isopropanol, products (S-1-phenylethanol and S-6-methyl-5-hepten-2-ol) were obtained with an enantiomeric excess of at least 99.9 % and a yield of 92 and 93% respectively. This strain was found to be tolerant to isopropanol and could effectively reduce 6-methyl-5-hepten-2-one to S-6-methyl-5-hepten-2-ol in a buffer containing 50% isopropanol.

A phytase preparation was obtained from the cells of haloalkalitolerant bacteria identified as Silvania hatchlandensis isolated from the soil of a soda sludge storage facility. When the enzyme was immobilized in barium alginate gel and cross-linked with activated chitosan, 97 and 95% of the native protein activity, respectively, was retained. It was shown that 70% of the phytase activity was retained when using the enzyme immobilized in alginate and bound to chitosan over 6 consecutive reaction cycles. Immobilization resulted in an insignificant decrease in the maximum reaction rate and a decrease in the Michaelis constant. Immobilized phytase was more thermally stable compared to the free form of the enzyme: the thermal inactivation constant of the immobilized enzyme at 70°C decreased by 1.1–1.2 times. The immobilized enzyme retained activity at pH 3–12; the pH optimum of the enzyme after immobilization did not change and was equal to 5.0. The specific activity of the enzyme covalently attached to activated chitosan is higher than that of the native enzyme in low and high pH environments. Immobilized phytase of haloalkalitolerant S. hatchlandensis can be used in feed production and other areas of agriculture.

The marine fungal strain KMM 4719 was isolated from the sea cucumber Apostichopus japonicus and identified as Penicillium polonicum based on three molecular genetic markers: ITS, BenA, and CaM. 3-O-methylviridicatin was isolated from the ethyl acetate extract of the strain culture. 3-O-methylviridicatin demonstrated cardioprotective activity for the first time, as well as urease inhibitory activity (IC₅₀ 97.3 μM). In addition, 3-O-methylviridicatin at a concentration of 100 μM (25.1 μg/ml) inhibited the growth of the yeast-like fungus Candida albicans at 23.2%.

For the first time, the genome of the dichloromethane destructor Methylobacterium dichloromethanicum subsp. dichloromethanicum DM4 was analyzed for the presence of genetic determinants indicating its potential as a plant growth stimulator, and the ability of this strain and its groEL2 gene mutant for the to improve plant growth was determined. The genome of strain DM4 contains genes involved in the biosynthesis of phytohormones (indolyl-3-acetic acid and cytokinins), siderophores, carotenoids, poly-β-hydroxybutyrate, hydrolytic enzymes, as well as enzymes involved in the degradation of D-cysteine, protection from UV-damage and phosphate solubilization. Inoculation of lettuce sprouts by strain DM4 had a positive effect on plant growth and development, and increased adaptive defense and resistance to short-term temperature stress in plant growth experiments. Comparative analysis of the production of auxins, siderophores, hydrolytic enzymes, D-cysteine desulfohydrase activity, and the ability to solubilize insoluble phosphates in strains DM4 and DM4 ΔgroEL2 showed that disruption of the groEL2 gene led to a decrease in the synthesis of indole derivatives and phosphate solubilizing ability in the mutant strain. Assessment of the impact of inoculation of lettuce plants by these strains also demonstrated a decrease in the phytostimulation potential of DM4 ΔgroEL2 compared to the original strain. The data obtained indicate that the chaperonin GroEL2 in M. dichloromethanicum subsp. dichloromethanicum DM4 indirectly affects its phytostimulation activity.

The work analyzed nine strains of Pectobacterium atrosepticum (Pca) and obtained new information about the properties of the pathogen and the regulation of its main virulence factors. Anionic groups (PO₃^4–) were identified in exopolysaccharides (EPS) of Pca, which differ in quantity among different strains and may contribute to the formation of denser biofilms. Most Pca strains inhibited the growth of potato plants in vitro to varying degrees, but one of them (strain 426) significantly activated this indicator in plants of the resistant potato variety Lugovskoy. Based on the totality of symptoms of the disease (chlorosis, necrosis, wilt, inhibition of growth rate), all strains of P. atrosepticum were divided according to the degree of virulence. In addition, it was shown that incubation of bacteria with a homogenate from potato plants in vitro modulated the activity of pectinase Pca: a homogenate from plants of the resistant potato variety Lugovskoy inhibited the activity of exopectinase, and from the susceptible variety Lugovskoy activated it. At the same time, the exopectinase activity of the avirulent strain 426 was inhibited to the greatest extent. It is assumed that this was the reason for stimulating the growth of potato plants in vitro of a resistant variety.