Improvement of karst soil nutrients by arbuscular mycorrhizal fungi through promoting nutrient release from the litter

Study of the Correlation Between Endophyte Abundances and Metabolite Levels in Different Parts of the Tissue of Cultivated and Wild Arnebia euchroma (Royle) Johnst. Based on Microbiome Analysis and Metabolomics

Arnebia euchroma (Royle) Johnst. has high medicinal and economic value, but in recent years, wild resources of this species have been depleted and the quality of artificially cultivated A. euchroma has been poor. The endophyte community of medicinal plants is rich, serving as an internal resource that promotes the growth of medicinal plants and the accumulation of secondary metabolites, and has important potential application value in improving the quality of medicinal materials. A. euchroma cultivars and wild varieties contain abundant endophyte communities and metabolites in different tissues. However, the relationships between A. euchroma endophytes and metabolites with different growth patterns and different tissue sites remain unclear. In this study, microbiome analysis and metabolomics were used to analyze the diversity of endophytes in the root and leaf tissues of cultivated and wild A. euchroma and their correlations with metabolites. The results revealed that the diversity of endophytes in A. euchroma was different from that in wild A. euchroma and that there was tissue specificity among different tissues. A species composition analysis revealed that the dominant endophytic fungi belonged to Ascomycota and Basidiomycota, and the dominant endophytic bacteria belonged to Proteobacteria and Cyanobacteria. A total of 248 metabolites, including quinones, flavonoids, alkaloids, organic acids, sugars, amino acids, coumarins, sterols, terpenoids, polyphenols, fatty ketones, and their derivatives, were identified in positive ion mode via LC-MS/MS. According to their different growth patterns and associated tissue parts, 9 differentially abundant metabolites were screened between AEZ-L (cultivated leaf tissue of A. euchroma) and AEY-L (wild leaf tissue of A. euchroma), 6 differentially abundant metabolites were screened between AEZ-R (cultivated root tissue of A. euchroma) and AEY-R (wild root tissue of A. euchroma), and 104 differentially abundant metabolites were screened between AEZ-R and AEZ-L. Eighty-two differentially abundant metabolites were screened between AEY-R and AEY-L. The contents of eight naphthoquinones in AEZ-R and AEY-R were determined via HPLC. The contents of β,β'-dimethylacrylylakanin in wild A. euchroma were greater than those in cultivated A. euchroma. A correlation analysis revealed that the dominant endophytes in the four groups were significantly correlated with a variety of metabolites, and the eight naphthoquinones in the root tissue were also significantly correlated with the dominant endophytes. The diversity of the A. euchroma endophyte community differed across different growth patterns and different tissue parts. There were significant differences in the relative contents of A. euchroma metabolites in different tissues. A correlation analysis verified the correlation between A. euchroma endophytes and metabolites.

Analysis of Salt Stress on Soil Microbial Community Composition and Its Correlation with Active Components in the Rhizosphere of Acanthopanax senticosus

Salt stress can adversely affect plant seed germination, growth and development, and eventually lead to slow growth and even death of plants. The purpose of this study was to investigate the effects of different concentrations of NaCl and Na2SO4 stress on the physicochemical properties, enzyme activities, rhizosphere microbial community and seven active components (L-phenylalanine, Protocatechuic acid, Eleutheroside B, Chlorogenic acid, Caffeic acid, Eleutheroside E, Isofraxidin) of Acanthopanax senticosus rhizosphere soil. Statistical analysis was used to explore the correlation between the rhizosphere ecological factors of Acanthopanax senticosus and its active components. Compared with Acanthopanax senticosus under NaCl stress, Na2SO4 generally had a greater effect on Acanthopanax senticosus, which reduced the richness of fungi in rhizosphere soil and adversely affected the content of multiple active components. Pearson analysis showed that pH, organic matter, ammonium nitrogen, available phosphorus, available potassium, catalase and urease were significantly correlated with active components such as Caffeic acid and Isofraxidin. There were 11 known bacterial genera, 12 unknown bacterial genera, 9 known fungal genera and 1 unknown fungal genus significantly associated with the active ingredient. Salt stress had great changes in the physicochemical properties, enzyme activities and microorganisms of the rhizosphere soil of Acanthopanax senticosus. In conclusion, different types and concentrations of salts had different effects on Acanthopanax senticosus, and the active components of Acanthopanax senticosus were regulated by rhizosphere soil ecological factors.

Positive effects of Cordyceps cateniannulata colonization in tobacco: Growth promotion and resistance to abiotic stress

Background

Entomopathogenic fungi can live in insects to cause disease and death and are the largest group of entomopathogenic microorganisms. Therefore, these fungi are best known for their microbial control potential. Importantly, they also have other beneficial effects, including promoting plant growth and development by colonizing plant. Here, the study sought to identify specific strains of the entomopathogenic fungus, Cordyceps cateniannulata that would form endophytic associations with tobacco, thus benefiting plant growth and resistance to abiotic stresses, thereby highlighting the application of entomopathogenic fungi in tobacco.

Methods

The C. cateniannulata-tobacco symbiont was constructed by root irrigation. The effects of C. cateniannulata on tobacco growth were evaluated by measuring the maximum leaf length, maximum leaf width, number of leaves, plant height, stem thickness, stem circumference, dry and fresh shoot weight 7, 14, 21, and 28 days after colonization. The peroxidase, catalase, superoxide dismutase, and malondialdehyde were measured to observe the impact of C. cateniannulata on tobacco defense enzyme activity. Finally, high-throughput sequencing was used to access microbial communities in the rhizosphere, with data subsequently linked to growth indicators.

Results

After tobacco was inoculated with C. cateniannulata X8, which significantly promoted growth and related enzyme activity, malondialdehyde was decreased. The most significant impact was on peroxidase, with its activity being upregulated by 98.20, 154.42, 180.65, and 170.38% in the four time periods, respectively. The high throughput sequencing results indicated that C. cateniannulata had changed the rhizosphere microbial relative abundances, such as increasing Acidobacteria and Ascomycetes, and decreasing Actinomycetes and Basidiomycetes. The redundancy analysis showed that C. cateniannulata significantly boosted tobacco growth by reducing the abundance of specific dominant genera such as Stachybotrys, Cephalotrichum, Streptomyces, Isoptericola, and Microbacterium.

Conclusion

Specific strains of C. cateniannulata can be introduced into host plants as endophytes, resulting in promotion of host plant growth and increased resistance to abiotic stress and microbial pathogens. The study provides a foundation for future studies of C. cateniannulata as an ecological agent.

Diversity and structural analysis of rhizosphere soil microbial communities in wild and cultivated Rhizoma Atractylodis Macrocephalae and their effects on the accumulation of active components

Rhizosphere microorganisms are the main factors affecting the formation of high quality medicinal materials and promoting the accumulation of secondary metabolites. However, the composition, diversity, and function of rhizosphere microbial communities in endangered wild and cultivated Rhizoma Atractylodis Macrocephalae (RAM) and their relationships with active component accumulation have remained unclear. In this study, high-throughput sequencing and correlation analysis were used to study the rhizosphere microbial community diversity (bacteria and fungi) of three RAM species and its correlation with the accumulation of polysaccharides, atractylone, and lactones (I, II, and III). A total of 24 phyla, 46 classes, and 110 genera were detected. The dominant taxa were Proteobacteria, Ascomycota, and Basidiomycota. The microbial communities in both wild and artificially cultivated soil samples were extremely species-rich, but there were some differences in their structure and the relative abundances of microorganism taxa. Meanwhile, the contents of effective components in wild RAM were significantly higher than those in cultivated RAM. Correlation analysis showed that 16 bacterial and 10 fungal genera were positively or negatively correlated with active ingredient accumulation. These results showed that rhizosphere microorganisms could play an important role in component accumulation and might lay a foundation for future research on endangered materials.

Petroleum pollution affects soil chemistry and reshapes the diversity and networks of microbial communities

Soil is the bearing centre of terrestrial ecosystems. Oil pollution leads to changes in the physical and chemical properties of soil to varying degrees. Polluted soils form a unique microbial species composition, which provides rich materials for the bioremediation of oil-contaminated soil through biological enhancement. Understanding the microbial composition of petroleum-contaminated soil can provide a better biological method for soil remediation. Based on this, 16 S rRNA and ITS genetic markers were used to analyse the bacterial and fungal microbiota in petroleum-contaminated soil, and their physical and chemical properties (total organic carbon, alkaline hydrolysable nitrogen, total phosphorus, total potassium, available potassium, Cu, Zn, and Cd) were measured. It was found that petroleum pollution can significantly reduce the abundance and diversity of bacteria and fungi in the soil and significantly promote the relative abundance of Proteobacteria, Pseudomonas, Pseudoxanthomonas and Pseudoallescheria, which changed the dominant flora of bacteria and fungi and reshaped the co-occurrence network relationship between bacteria and fungi in oil-contaminated soil. The content of total organic carbon in petroleum-contaminated soil was significantly higher than that in uncontaminated soil, while the content of alkaline hydrolysable nitrogen and available potassium was significantly lower than that in uncontaminated soil, and the content of Cu significantly increased after pollution. Total organic carbon is the key driving factor that changes oil-contaminated soil microorganisms and plays a significant role in regulating the remodelling and composition of the microbial community in oil-contaminated soil. This study laid a solid theoretical foundation for the bioremediation of oil-contaminated soil.

Heterogeneity of Spatial-Temporal Distribution of Nitrogen in the Karst Rocky Desertification Soils and Its Implications for Ecosystem Service Support of the Desertification Control—A Literature Review

In recent years, the study of soil nitrogen distribution (SND) in rocky desertification control ecosystems has increased exponentially. Rocky desertification experiences severe environmental degradation due to its fragile nature, and understanding rocky desertification soil nitrogen (SN) is critical for ecosystem services (ES) to support sustainable development. From the perspective of bibliometrics, this paper systematically, comprehensively, qualitatively and quantitatively describes the progress, trends and hotspots of SND in the field of rocky desertification environment. The results show that: 97.40% of the document type is “Article”; the study of rocky desertification SND shows the characteristics of rapid growth, the volume of published articles in the past three years accounted for 34.30% of the total; active countries are mainly China, Germany, United States, Sweden, Finland, etc. The research hotspots in this field include karst and nitrogen, and the future research hotspots tend to focus on karst rocky desertification ecosystem, soil nutrients and vegetation diversity in south China. It is suggested to construct SN management strategy suitable for rocky desertification fragile ecosystems in the future, strengthen theoretical research and comprehensively understand the characteristics of rocky desertification control ecosystem to put forward sustainable management strategy according to local conditions.