Metagenomic analysis of soil microbial communities associated with Poa alpigena Lindm in Haixin Mountain, Qinghai Lake.

To investigate the impact of Poa alpigena Lindm on rhizosphere and bulk soil microorganisms in Haixin Mountain, Qinghai Lake, this study employed metagenomics technology to analyze the microbial communities of the samples. Results showed that 65 phyla, 139 classes, 278 orders, 596 families, 2376 genera, and 5545 species of soil microorganisms were identified from rhizosphere and bulk soil samples. Additionally, a microbial gene library specific to Poa alpigena Lindm was established for Qinghai Lake. Through α-diversity analysis, the richness and diversity of bulk microorganisms both significantly had a higher value than that in rhizosphere soil. The indicator microorganisms of rhizosphere and bulk soil at class level were Actinobacteria and Alphaproteobacteria, respectively. KEGG pathway analysis indicated that Carotenoid biosynthesis, Starch and sucrose metabolism, Bacterial chemotaxis, MAPK signaling pathway, Terpenoid backbone biosynthesis, and vancomycin resistance were the key differential metabolic pathways of rhizosphere soil microorganisms; in contrast, in bulk soil, the key differential metabolic were Benzoate degradation, Glycolysis gluconeogenesis, Aminobenzoate degradation, ABC transporters, Glyoxylate and dicarboxylate metabolism, oxidative phosphorylation, Degradation of aromatic compounds, Methane metabolism, Pyruvate metabolism and Microbial metabolism diverse environments. Our results indicated that Poa alpigena Lindm rhizosphere soil possessed selectivity for microorganisms in Qinghai Lake Haixin Mountain, and the rhizosphere soil also provided a suitable survival environment for microorganisms.

The antimicrobial effect and mechanism of the Artemisia argyi essential oil against bacteria and fungus.

Artemisia argyi is a traditional Chinese herb with antibacterial, antifungal, and antitumor activities. The essential oil of Artemisia argyi was extracted using the steam distillation method in this study. The chemical composition of the essential oil was analyzed using the gas chromatography-mass spectrometry method. Agar disc diffusion and double-broth dilution assays were used to detect the antimicrobial activity of the essential oil. Subsequently, the antimicrobial mechanisms were explored through cytomembrane permeability assay and electron microscopy. Based on gas chromatography-mass spectrometry analysis, 25 compounds were detected, including 13.76% cineole, 6.77% terpinen-4-ol, 6.68% 3-dione, 1,7,7-trimethyl-, 4.07% 3-cyclohexen-1-ol, 4-methyl-1-(1-methylethyl)-acetate, 3.58% 1-isopropyl-2-methylbenzene, and 1.58% g-terpinene. The essential oil was tested for antimicrobial activity, and the IC50 values for Staphylococcus aureus, Escherichia coli, Bacillus subtilis, Listeria monocytogenes, Pseudomonas aeruginosa, Streptococcus pneumoniae, and Candida albicans were determined to be 25.51 ± 2.29, 49.53 ± 0.86, 52.40 ± 1.49, 52.76 ± 1.60, 73.99 ± 1.38, 65.52 ± 0.95, and 214.98 ± 3.27 µg mL-1, respectively. For essential oil interaction with cytoderm, the microorganisms treated by 1 × IC50 and 2 × IC50 concentration of essential oil both represented positive test results. Additionally, the alkaline phosphatase levels showed a direct correlation with concentration and treatment duration (range from 0 to 8 h). The interaction between essential oils and the cytomembrane was investigated by examining samples containing one of three test strains (Staphylococcus aureus, Escherichia coli, and Candida albicans), essential oil, and voltage-sensitive fluorescent dye disc35. The results demonstrated a significant increase in fluorescence levels within the solution upon introduction of the essential oil-treated strains. The findings of our research suggest that the essential oil disrupts the cytoderm and cytomembrane, thereby exhibiting antimicrobial activity.