Antibacterial Ingredients and Modes of the Methanol-Phase Extract from the Fruit of Amomum villosum Lour.

Epidemics of infectious diseases threaten human health and society stability. Pharmacophagous plants are rich in bioactive compounds that constitute a safe drug library for antimicrobial agents. In this study, we have deciphered for the first time antibacterial ingredients and modes of the methanol-phase extract (MPE) from the fruit of Amomum villosum Lour. The results have revealed that the antibacterial rate of the MPE was 63.64%, targeting 22 species of common pathogenic bacteria. The MPE was further purified by high performance liquid chromatography (Prep-HPLC), and three different constituents (Fractions 1-3) were obtained. Of these, the Fraction 2 treatment significantly increased the cell membrane fluidity and permeability, reduced the cell surface hydrophobicity, and damaged the integrity of the cell structure, leading to the leakage of cellular macromolecules of Gram-positive and Gram-negative pathogens (p < 0.05). Eighty-nine compounds in Fraction 2 were identified by ultra HPLC-mass spectrometry (UHPLC-MS) analysis, among which 4-hydroxyphenylacetylglutamic acid accounted for the highest 30.89%, followed by lubiprostone (11.86%), miltirone (10.68%), and oleic acid (10.58%). Comparative transcriptomics analysis revealed significantly altered metabolic pathways in the representative pathogens treated by Fraction 2 (p < 0.05), indicating multiple antibacterial modes. Overall, this study first demonstrates the antibacterial activity of the MPE from the fruit of A. villosum Lour., and should be useful for its application in the medicinal and food preservative industries against common pathogens.

[Effects of Short-Term Nitrogen and Phosphorus Addition on Soil Respiration Components in a Subalpine Grassland of Qilian Mountains].

In order to investigate the effects of short-term nitrogen and phosphorus addition on soil respiration and its components in a subalpine grassland located on the Qilian Mountains, a random block design of nitrogen[10 g·(m2·a)-1, N], phosphorus[5 g·(m2·a)-1, P], nitrogen and phosphorus addition[10 g·(m2·a)-1N and 5 g·(m2·a)-1P, NP], the control (CK), and complete control (CK') was conducted from June to August 2019, and total soil respiration and its component respiration rates were measured. The results showed that nitrogen addition reduced soil total respiration and heterotrophic respiration rates at a lower rate than P addition[-16.71% vs. -19.20%; -4.41% vs. -13.05%], but the rate of decrease in autotrophic respiration was higher than that of P addition (-25.03% vs. -23.36%); N and P mixed application had no significant effect on soil total respiration rate. The total soil respiration rate and its components were significantly exponentially correlated with soil temperature, and the temperature sensitivity of soil respiration rate was decreased by nitrogen addition (Q10:-5.64%-0.00%). P increased Q10 (3.38%-6.98%), and N and P reduced autotrophic respiration rate but increased heterotrophic respiration rate Q10 (16.86%) and decreased total soil respiration rate Q10 (-2.63%- -2.02%). Soil pH, soil total nitrogen, and root phosphorus content were significantly correlated with autotrophic respiration rate (P<0.05) but not with heterotrophic respiration rate, and root nitrogen content was significantly negatively correlated with heterotrophic respiration rate (P<0.05). In general, autotrophic respiration rate was more sensitive to N addition, whereas heterotrophic respiration rate was more sensitive to P addition. Both N and P addition significantly reduced soil total respiration rate, whereas N and P mixture did not significantly affect soil total respiration rate. These results can provide a scientific basis for the accurate assessment of soil carbon emission in subalpine grassland.

Nitrogen effects on grassland biomass production and biodiversity are stronger than those of phosphorus.

Human-induced nitrogen (N) and phosphorus (P) enrichment have profound effects on grassland net primary production (NPP) and species richness. However, a comprehensive understanding of the relative contribution of N vs. P addition and their interaction on grassland NPP increase and species loss remains elusive. We compiled data from 80 field manipulative studies and conducted a meta-analysis (2107 observations world-wide) to evaluate the individual and combined effects of N and P addition on grassland NPP and species richness. We found that both N addition and P addition significantly enhanced grassland above-ground NPP (ANPP; 33.2% and 14.2%, respectively), but did not affect total NPP, below-ground NPP (BNPP), and species evenness. Species richness significantly decreased with N addition (11.7%; by decreasing forbs) probably due to strong decreased soil pH, but not with P addition. The combined effects of N and P addition were generally stronger than the individual effects of N or P addition, and we found the synergistic effects on ANPP, and additive effects on total NPP, BNPP, species richness, and evenness within the combinations of N and P addition. In addition, N and P addition effects were strongly affected by moderator variables (e.g. climate and fertilization type, duration and amount of fertilizer addition). These results demonstrate a higher relative contribution of N than P addition to grassland NPP increase and species loss, although the effects varied across climate and fertilization types. The existing data also reveals that more long-term (≥5 years) experimental studies that combine N and P and test multifactor effects in different climate zones (particularly in boreal grasslands) are needed to provide a more solid basis for forecasting grassland community response and C sequestration response to nutrient enrichment at the global scale.

Low temperature route synthesis of SiC-Al2O3 hetero-structural nanofibers.

SiC-Al2O3 hetero-structural nanofibers have been synthesized by the chemical solution approach at 200 ° C. The diameters of nanofibers are in the range of 60-100 nm while the lengths are from tens of micrometers to hundreds of micrometers. The microstructural analysis shows that the fibers possess a like-epitaxial relationship between (104) of hexagonal Al2O3 and (111) of cubic SiC. Additionally, the optical investigation of the nanofibers suggests there are some defects in the low annealing temperature synthesized SiC-Al2O3 nanofibers.