The chemical composition of hyssop oil from Bulgaria was determined by gas chromatography with flame ionization detection and gas chromatography–mass spectrometry on two different chromatographic columns. The quantity of identified compounds was shown correspond to 97.2% and 98% of the total oil content. Among the detected compounds, cis-pinocamphone (48.98%–50.77%), β-pinene (13.38%–13.54%), trans-pinocamphone (5.78%–5.94%) and β-phellandrene (4.44%–5.17%) were the major compounds. Hyssop oil demonstrated antifungal activity against 52 clinical isolates and reference strains of Candida albicans, Candida glabrata, Candida tropicalis, Candida parapsilosis and Candida krusei. The essential oil characterized with stronger antifungal activity in comparison with pure cis- and trans-pinocamphone, α- and β-pinene and β-phellandrene. Essential oil of Hyssopus officinalis L. from Bulgaria inhibited both fluconazol-sensitive and fluconazol-resistant strains.

Concentrated extraction products (concrete, resinoid, extract with 1,1,1,2-tetrafluoroethane) from the leaves of three Bulgarian types of tobacco (Nicotiana tabacum L.) – flue-cured Virginia, Burley and Oriental, have been obtained. The products, as well as the respective essential oils, have been characterized by their chemical composition (mono-, sesqui- and diterpenoids, phenylpropanoids, nitrogenous compounds, etc., and phenolic acids) and activities (antimicrobial, anticorrosion). The studied extracts demonstrated antimicrobial activity against Gram-positive, Gram-negative bacteria and yeasts. The obtained results reveal the differences both on product and raw material (tobacco type) basis, and mark the possible fields of their application.

Microbial communities drive the biogeochemical cycles in wetlands and provide a number of ecosystem services. They underpin soil function, and are easily impacted by anthropogenic pressure. This study examined the bacterial microbiome in the natural wetland of Zlato Pole and the protected, periodically flooded rice paddies in the Maritsa River Basin using a metagenomic approach, based on high-throughput sequencing. Alpha-diversity analysis showed a significant variation between the three study sites for Chao1 and ACE (abundance based coverage estimator) richness estimators. A positive correlation was established with pH, with highest values detected for the rice paddies and the lowest, for the Zlato Pole sediments. The obtained sequences were assigned into 37 known bacterial phyla with over 97% bacterial sequences classified within only nine of them. The bacterial communities in rice paddies sediments were more evenly distributed, whereas the Zlato Pole sediment was the most biased. The consortiums in the rice paddies were dominated by Proteobacteria, followed by Actinobacteria and Acidobacteria. The bacterial assemblages in those sites could not be distinguished by analysis of similarity. The Zlato Pole sediment community held an isolated position, where Acidobacteria was replaced by Firmicutes and Bacteroidetes and the microbiome showed an extremely high abundance of Gammaproteobacteria and Bacilli. The dominance of Gammaproteobacteria and the presence of Deinococcus-Thermus phylum, along lower nutrient concentration and the absence of correlation with the environmental parameters, is evidence of constant anthropogenic pressure around the area. The obtained results could be applied in the plans for sustainable management of the protected wetlands.

Lactobacillus is a key genus of probiotics commonly utilized for the treatment of oral infections The primary aim of our research was to investigate the probiotic potential of the newly isolated Levilactobacillus brevis DPL5 strain from human breast milk, focusing on its ability to combat biofilm-forming pathogens such as Staphylococcus aureus. Employing in vitro approaches, we demonstrate L. brevis DPL5′s ability to endure at pH 3 with survival rates above 30%, and withstand the osmotic stress often found during industrial processes like fermentation and freeze drying, retaining over 90% viability. The lyophilized cell-free supernatant of L. brevis DPL5 had a significant antagonistic effect against biofilm-producing nasal strains of Staphylococcus aureus, and it completely eradicated biofilms at subinhibitory concentrations of 20 mg·mL⁻¹. Higher concentrations of 69 mg·mL⁻¹ were found to have a 99% bactericidal effect, based on the conducted probability analysis, indicating the production of bactericidal bioactive extracellular compounds capable of disrupting the biofilm formation of pathogens like S. aureus. Furthermore, genome-wide sequencing and analysis of L. brevis DPL5 with cutting-edge Nanopore technology has uncovered over 50 genes linked to probiotic activity, supporting its ability to adapt and thrive in the harsh gut environment. The genome also contains multiple biosynthetic gene clusters such as lanthipeptide class IV, Type III polyketide synthase (T3PKS), and ribosomally synthesized, and post-translationally modified peptides (RiPP-like compounds), all of which are associated with antibacterial properties. Our study paves the way for the further exploration of DPL5, setting the stage for innovative, nature-inspired solutions to combat stubborn bacterial infections.