The modern paradigm assumes that interspecies communication of microorganisms occurs through precise regulatory mechanisms. In particular, antagonism between bacteria or bacteria and fungi can be achieved by direct destruction of the targeted cells through the regulated production of antimicrobial metabolites or by controlling their adaptive mechanisms, such as the formation of biofilms. The quorum-quenching phenomenon provides such a countermeasure strategy. This review discusses quorum-sensing suppression by Gram-positive microorganisms, the underlying mechanisms of this process, and its molecular intermediates. The main focus will be on Gram-positive bacteria that have practical applications, such as starter cultures for food fermentation, probiotics, and other microorganisms of biotechnological importance. The possible evolutionary role of quorum-quenching mechanisms during the development of interspecies interactions of bacteria is also considered. In addition, the review provides possible practical applications for these mechanisms, such as the control of pathogens, improving the efficiency of probiotics, and plant protection.

Restoring and improving soil fertility, increasing the productivity of cultivated plants is one of the objectives of agricultural production. The aim of the present work was to study the antagonistic interactions between the soil bacteria of the order Bacillales and phytopathogenic fungi. The spore-forming soil bacteria attract increasing interest as biocontrol agents, but little is known about the influence of local soil conditions on the development of antagonism in indigenous bacterial strains. This can lead to unsuccessful attempts of bacterial antagonists isolation. To determine the sequences of primary nucleotide DNA, the authors used the Sanger sequencing method, the detection of sequencing products was performed automatically, using themethod of capillary electrophoresis. Homology of at least 97% was considered as the criterion for classifying a microorganism as a certain species. This study presents new data on the influence of soil type and preceding crop on the level of antagonism against Fusarium and Plectosphaerella. The results show that both the soil type and preceding crop influence the fungal-bacterial antagonistic interactions. The strongest antagonistic activity among all bacterial isolates was found in bacteria isolated from AlbicPhaeozem. The highest antagonistic activity against F. graminearum was shown by strains that were isolated from soils on which winter wheat was the preceding crop.

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Aim of the study – the development of a method for obtaining a tumor xenograft model by a subcutaneous transplantation of a porous metal scaffold populated with cultured human lung carcinoma cells. Material and methods. The study included 14 athymic male Balb c/nude mice aged 8-90 weeks, weighing 20-24 g. All animals received injections with cultured human A549 lung carcinoma cells subcutaneously into the right anterolateral area of the back. In animals of the main group (gr.1, n=4), scaffolds with a pore diameter of 0.5 mm made of titanium-aluminum-vanadium alloy using an industrial 3D printer served as carriers of tumor cells. Scaffolds were seeded with 3 million A549 culture cells, and were implanted into the recipient animals after the 7-day incubation. Results were compared with the results of the tumor culture transplantation with Matrigel (100 mcL) in two groups of animals with varying cell suspension dosages: the maximum vaccination dose for in vivo (10×106 cells per mouse, gr.2, n=5) and half the maximum dose (5×106 respectively, gr.3, n=5). Then, the dynamics of tumor growth in the groups of experimental mice was monitored for 55 days: xenograft volumes were calculated using the Shrek’s formula for an ellipsoid. At the end of the experiment, the animals were euthanized by cervical dislocation. Results. Monitoring of the dynamics of xenograft volumes demonstrated the maximal values in mice with implanted scaffolds. The slowest xenograft growth was registered in animals with the maximum vaccination dose of tumor cells with Matrigel. Histological study showed that tumor material obtained from all animals corresponded to A549 lung carcinoma. Conclusions. Porous metal scaffolds, previously incubated with A549 culture cells and implanted subcutaneously in athymic Balb c/nude mice, allows obtaining rapidly growing xenografts with histologically confirmed correspondence to the original tumor.