Жарияланымдар / Публикации

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Тема: search.filters.subject.Gram-positive bacteria

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    Culturable rhizosphere bacteria associated with Alcea nudiflora (Lindl.) Boiss. in the Zailiyskiy Alatau (Kazakhstan): isolation, characterization and functional potential
    (Instituto Internacional de Ecologia (Brazil), 2026-01-01)
    Akerke Abil
    ;
    Kadir Akan
    ;
    Zhansaya Abdukadirova
    ;
    Damira Yussayeva
    ;
    G. D. Ultanbekova
    Abstract The rhizosphere of medicinal plants represents a reservoir of culturable bacteria with potential value for plant protection and biotechnology. In this study, we characterized the culturable rhizosphere bacterial community associated with Alcea nudiflora (Lindl.) Boiss. collected from three sites in the Zailiyskiy Alatau. Rhizosphere microorganisms were isolated using tenfold serial dilutions followed by plating on meat-peptone agar and oatmeal agar, purified by streaking, and phenotypically characterized by colony morphology, Gram staining, and motility assays. Nineteen morphologically distinct isolates were recovered and grouped into four morphotypes: Streptomyces-like actinomycetes, Bacillus-like spore-forming rods, coryneform bacteria, and coccoid forms. All isolates showed a Gram-positive reaction. Antagonistic activity was screened using agar well diffusion, disk diffusion, and agar block assays against test microorganisms (Escherichia coli, Staphylococcus aureus, Candida albicans, C. utilis, Aspergillus niger, Fusarium oxysporum and Penicillium chrysogenum). Several isolates exhibited broad or target-specific antagonism, including strains 5/1 (balanced antibacterial and antifungal activity), 4/7 and 7/1 (anti-staphylococcal activity), 9/3 and 8/2 (antifungal activity, including against Candida spp.), and 1/2 (specific activity against A. niger). Overall, these results provide a baseline characterization of the culturable rhizosphere bacteria associated with Alcea nudiflora (Lindl.) Boiss. in this region and identify candidate isolates for molecular identification and plant-focused validation.
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    Phosphonamidates Integrating Sterically Hindered Phenols with Membrane-Active Cations: A Redox-Activated Approach to Antimicrobial Agents
    (Multidisciplinary Digital Publishing Institute, 2026-05-18)
    Elmira Gibadullina
    ;
    Adel Shakirov
    ;
    Margarita Neganova
    ;
    Yulia Aleksandrova
    ;
    Alexandra Voloshina
    A strategy to create highly effective antimicrobial agents was proposed based on the conjugation of three functional components: a cationic quaternary ammonium salt (QAS) that exerts a membrane-disrupting effect and promotes selective accumulation on bacterial surfaces; a phosphonamidate linker for controlled activation; and a sterically hindered phenol (SHP) fragment as a potential redox component. This approach enabled the preparation of 40 target phosphonamidate–SHP/QAS hybrids in high yields (88–98%). Evaluation of their antimicrobial activity against major pathogens and methicillin-resistant Staphylococcus aureus (MRSA) revealed high potency against Gram-positive bacteria. The lead compounds achieved minimum inhibitory concentration (MIC) values of 0.7–2.8 μM, which is up to 10 times lower than that of the reference drug, norfloxacin. Mechanistic studies confirmed that these hybrids disrupt the bacterial membrane. In addition, an increase in intracellular ROS levels was observed for the most active compound. The SHP/QAS hybrids retained high activity against S. aureus ATCC 209P after 17 passages and showed low cytotoxicity (SI = 62–92) and negligible hemolysis. These properties indicate that this approach may offer a useful strategy for developing antibacterial agents with a potentially lower risk of inducing conventional resistance mechanisms.