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A Lactobacillus delbrueckii ssp. lactis strain named A4, isolated from the gut of an Armenian honeybee, was subjected to a probiogenomic characterization because of its unusual origin. A whole-genome sequencing was performed, and the bioinformatic analysis of its genome revealed a reduction in the genome size and the number of the genes-a process typical for the adaptation to endosymbiotic conditions. Further analysis of the genome revealed that Lactobacillus delbrueckii ssp. lactis strain named A4 could play the role of a probiotic endosymbiont because of the presence of intact genetic sequences determining antioxidant properties, exopolysaccharides synthesis, adhesion properties, and biofilm formation, as well as an antagonistic activity against some pathogens which is not due to pH or bacteriocins production. Additionally, the genomic analysis revealed significant potential for stress tolerance, such as extreme pH, osmotic stress, and high temperature. To our knowledge, this is the first report of a potentially endosymbiotic Lactobacillus delbrueckii ssp. lactis strain adapted to and playing beneficial roles for its host.

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The study of effects of Ca2+ and Mg2+ on antifungal activity of lactic acid bacteria (LAB) isolates and their associations revealed inducing and inhibiting effects on antifungal activity. The addition of Ca2+ essentially inhibited the antifungal effect of L. rhamnosus MDC9661 but stimulated the activity of RIN-2003-Ls, MDC9632 and MDC9633 strains, as well as their associations. Mg2+ partly increased the inhibitory activity of LAB isolates, while the addition of ions combination did not cause changes of their antifungal activity. The supplementation of Ca2+ stimulated the antifungal effect of most associations against Penicillium sp., Trichoderma viride, Geotrichum candidum, and Aspergillus flavus compared with the native conditions. The addition of Mg2+ induced the antifungal activity of RIN-2003-Ls, MDC9632, MDC9633, and INR-2010-Tsov-G-St combinations. The antifungal effects of most associations were increased in the presence of ions mixture. The natural LAB associations including VKPM B-3386, MDC9632, and MDC9633 could not suppress the growth of any tested mold; however, the supplementation of ions combination revealed their antifungal effect against all kinds of molds. The finding of substantial stimulation of the most LAB associations antifungal effect by metal ions can be basis for creation of new effective antifungal preparations by the supplementation of ions combined mixture.

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BACKGROUND: The newly created associations of lactic acid bacteria (LAB) isolated from Armenian dairy products (yoghurt, sour cream and different varieties of cheese), as well as from the gastrointestinal tract of honeybees were screened according to their antifungal and antibacterial activity. RESULTS: LAB strains were mixed at equal proportions (1:1) according to mathematical planning of experiments. Antifungal and antibacterial effects of different combinations (associations) were determined in different media, employing well-diffusion and total diffusion into agar methods. A number of fungal and bacterial test-organisms, including pathogenic ones, were used. Pure LAB strain cultures were used as a control. The antifungal effect of the most active strain Lactobacillus rhamnosus MDC 9661 in the associations with other LAB strains was partly decreased. At the same time, some mixed LAB cultures in DeMan, Rogosa and Sharpe (MRS) medium demonstrated significant antibacterial activity against wide spectra of test-organisms only in the case of simultaneous cultivation of LAB strains. On the other hand, in the case of different LAB strains cultivated in MRS with 24-h time break between mix formations by different strains, no inhibitory activity was revealed. But the inhibitory effect of many LAB associations against test-organisms was significantly increased in the case of separated cultivation in milk. CONCLUSION: The inhibitory effect of mixed LAB associations showed stronger dependence on the cultivation media and on the duration of cultivation with respect to each other. The co-cultivation of some strains, like L. rhamnosus MDC 9661, could lead to changed antagonistic activity. Consequently, the results are significant for creation and further investigation of LAB associations, as effective probiotics, and for their probable application in the production of antimicrobial preparations.

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The effects of divalent cations of Ca and Mg on antibacterial activity of lactic acid bacteria (LAB) isolates, as well as their different associations were studied. Most LAB strains and associations revealed significant inhibitory effects in MRS against Gram-positive and Gram-negative test-organisms at different Ca2+ and Mg2+ concentrations (determined specifically for each LAB strain and each association). Some LAB strains and communities inhibited the growth of pathogenic test-organisms depending on both ions concentrations and cultivation conditions. Interestingly, the presence of Mg ions in medium significantly decreased the antimicrobial activity of LAB communities against pathogenic test-organisms; on the other hand, the combined mixture of ions essentially increased the inhibitory effect in case of time-spaced cultivation. In contrast, the inhibitory effects of many associations were significantly increased at the presence of Mg2+ and especially ions combination in case of simultaneous cultivation. The addition of ions combination didn't affect antibacterial activity of LAB isolates. The results allow us to conclude that Ca and Mg ions had inducible effects on antibacterial activity in case of simultaneous cultivation. This probably can be prospective for creation of new antimicrobial preparations and their possible application.

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Different strains of lactobacilli isolated from Armenian dairy products (matsoun, sour cream and different types of cheeses), were studied for antifungal activity. Lactobacillus rhamnosus MDC 9661 strain was shown to have inhibitory activity against Penicillium aurantioviolaceum and Mucor plumbeus growth. Bacterial cell-free supernatant didn't show antifungal activity. The L. rhamnosus antifungal activity was stable to the wide range of pH from 3 to 10. This activity was high after treatment with both low temperature (- 30 °C) and lysozyme and with ultrasound. However, it was sensitive to high temperature from 45 to 80 °C and proteolytic enzymes. The results suggest the proteinaceous nature of L. rhamnosus antifungal activity associated with bacterial cell wall. L. rhamnosus MDC 9661 could be recommended as a starter for production of dairy products, functional food and preserving strain in food production.

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C-type lectin from hen egg shell as a recognition ligand for detection of St. aureus was applied. Three approaches for detection of bacteria were used and the sensitivities of the assays were compared. Two of them included spherical and anisotropic silver nanoparticles sensitized by lectin. In these cases the optical changes as a result of interaction of sensitized nanoparticles with bacteria were measured. In the third approach hybrid system of CdSe quantum dots-anisotropic silver nanoparticles sensitized by lectin was applied. Here fluorescent changes as a result of resonance energy transfer between nanoparticles as consequence of their interaction with bacteria were measured. The data demonstrate that assays with spherical silver nanoparticles permit to detect St. aureus in the range of 6 × 104/mL-2 × 107/mL, anisotropic silver nanoparticles in the range of 2 × 105/mL-1 × 108/mL, CdSe-Ag hybrid system in the range of 6 × 103/mL-2 × 107/mL. The data demonstrate that hybrid system CdSe-Ag with resonance energy transfer provides the best sensitivity.

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Lactobacillus rhamnosus R-2002 strain isolated from Armenian pickled cheese sample has a fungicide effect, which was carried out by the first-time designed method. The fungicide effect of LAB strain was expressed after 5 days of co-cultivation with Mucor plumbeus and 6 days of co-cultivation with Penicillium aurantioviolaceum. The growth as well as the antifungal activity of L. rhamnosus R-2002 was shown to directly depend on the nature of the medium's carbon source. The antifungal activity of this strain against both moulds was inhibited when the combination of 10 g l-1 glucose and 10 ml l-1 ethanol in the medium was used as a carbon source. The results could be applied in food industry, medicine, and veterinary.

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BACKGROUND: Human and animal skin diseases of bacterial, fungal and viral nature and their complications are widespread and globally cause a serious trouble. Their prevalence is increasing mainly due to drug resistance. Consequently, demand has increased for new effective antimicrobial drugs, which also should be less toxic, possess a wider spectrum of action and be economically more beneficial. The goal was to investigate antibacterial, antifungal and anti-phage activity of Petamcin-A-a new multicomponent preparation. It contains acetic acid and hexamethylenetetramine as main active antimicrobial components, as well as phosphatidylcholine, tocopheryl acetate and glycerol as excipients. METHODS: Bacteriostatic activity and minimal inhibitory concentrations of the preparation against various test-organisms were determined by agar well diffusion assay. Antifungal activity was tested by agar dilution assay. To explore anti-phage activity double agar overlay plaque assay was used. Nystatin, chlorhexidine and acetic acid were used as control agents for comparative analysis. Statistical analysis was done with GraphPad Prism 5.03 or R 3.1.0 software. RESULTS: The results showed a higher activity of Petamcin-A against all bacterial and fungal test strains compared with its components or control agents. The preparation was more effective against tested gram-positive bacteria than gram-negative ones. Petamcin-A expressed bactericidal activity against almost all test strains. In addition, the preparation demonstrated high activity against T4 phage of Escherichia coli C-T4 completely inhibiting its growth. 5-fold diluted Petamcin-A also exhibited considerable activity reducing phage concentration by 2.6 Log10. CONCLUSIONS: Petamcin-A has a high antimicrobial activity against all tested strains of bacteria, yeasts and moulds. The preparation also exhibited high anti-phage activity. Moreover, taking into account that Petamcin-A has no observable toxicity on skin and its components are not expensive, it can be advantageous for management of various skin medical conditions.

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A method of bacteria detection by sensitized anisotropic silver nanoparticles is presented. Anisotropic silver nanoparticles with two bands of surface plasmon resonance (SPR) are prepared and sensitized with potato lectin. These nanoparticles are able to detect three bacterial species: Escherichia coli, Bacillus subtilis and Staphylococcus aureus. The interaction of these bacteria with such nanoparticles induces drastic changes in optical spectra of nanoparticles that are correlated with bacteria titer. The maximal sensitivity is observed for S. aureus (up to 1.5×10(4) mL(-1)).

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