This study sought to analyze the main antibacterial active components of Lactobacillus pentosus (L. pentosus) L-36 cell-free culture supernatants (CFCS) in inhibiting the growth of Staphylococcus ...aureus (S. aureus), to explore its physicochemical properties and anti-bacterial mechanism. Firstly, the main antibacterial active substance in L-36 CFCS was peptides, which inferred by adjusting pH and enzyme treatment methods. Secondly, the physicochemical properties of the antibacterial active substances in L-36 CFCS were studied from heat, pH, and metal ions, respectively. It demonstrated good antibacterial activity when heated at 65 °C, 85 °C and 100 °C for 10 and 30 min, indicating that it had strong thermal stability. L-36 CFCS had antibacterial activity when the pH value was 2–6, and the antibacterial active substances became stable with the decrease in pH value. After 10 kinds of metal ions were treated, the antibacterial activity did not change significantly, indicating that it was insensitive to metal ions. Finally, scanning electron microscopy, transmission electron microscopy and fluorescence probe were used to reveal the antibacterial mechanism of S. aureus from the aspects of cell morphology and subcellular structure. The results demonstrated that L-36 CFCS could form 1.4–2.3 nm pores in the cell membrane of S. aureus, which increased the permeability of the bacterial cell membrane, resulting in the depolarization of cell membrane potential and leakage of nucleic acid protein and other cell contents. Meanwhile, a large number of ROS are produced and accumulated in the cells, causing damage to DNA, and with the increase in L-36 CFCS concentration, the effect is enhanced, and finally leads to the death of S. aureus. Our study suggests that the main antibacterial active substances of L-36 CFCS are peptides. L-36 CFCS are thermostable, active under acidic conditions, insensitive to metal ions, and exhibit antibacterial effects by damaging cell membranes, DNA and increasing ROS. Using lactic acid bacteria to inhibit S. aureus provides a theoretical basis for the discovery of new antibacterial substances, and will have great significance in the development of antibiotic substitutes, reducing bacterial resistance and ensuring animal food safety.
Methane (CH4) is an important greenhouse as well as a chemically active gas. Accurate monitoring and understanding of its spatiotemporal distribution are crucial for effective mitigation strategies. ...Nowadays, satellite measurements are widely used for CH4 studies. Here, we use the CH4 products from four commonly used satellites (GOSAT, TROPOMI, ARIS, and IASI) during the period from 2018 to 2020 to investigate the spatiotemporal variations of CH4 in China. In spite of the same target (CH4) for the four satellites, differences among them exist in terms of the instrument, spectrum, and retrieval algorithm. The GOSAT and TROPOMI CH4 retrievals use shortwave infrared spectra, with a better sensitivity near the surface, while the IASI and AIRS CH4 retrievals use thermal infrared spectra, showing a good sensitivity in the mid–upper troposphere but a weak sensitivity in the lower troposphere. The GOSAT and TROPOMI observe high CH4 concentrations in the east and south and low concentrations in the west and north, which is highly related to the CH4 emissions. The IASI and AIRS show a more uniform CH4 distribution over China, which reflects the variation of CH4 at a high altitude. However, a large discrepancy is observed between the IASI and AIRS despite using a similar retrieval band, e.g., significant differences in the seasonal variations of CH4 are observed between the IASI and AIRS across several regions in China. This study highlights the CH4 differences observed by the four satellites in China, and caution must be taken when using these satellite products.
Methane (CH
4
) is one of the most important greenhouse gases in the atmosphere, making it worthwhile to study its temporal and vertical distributions in source areas, e.g., North China. For this ...purpose, a ground-based high-resolution Fourier transform infrared spectrometer (FTIR), the Bruker IFS 125HR, along with an in-situ instrument, the Picarro G2301, were deployed in Xianghe County (39.8°N,117.0°E), Hebei Province, China. Data have been recorded since June 2018. For the FTIR measurements, we used two observation modes to retrieve the mole fraction of CH
4
: the Total Carbon Column Observing Network (TCCON) method (retrieval algorithm: GGG2014), and the Network for the Detection of Atmospheric Composition Change (NDACC) method (retrieval algorithm: SFIT4). Combining FTIR with in-situ measurements, we found the temporal and vertical distributions of atmospheric CH
4
within three vertical layers (near the ground, in the troposphere, and in the stratosphere), and throughout the whole atmosphere. Regarding the diurnal variation of CH
4
near the ground, the concentration at night was higher than during the daytime. Regarding the seasonal variation, CH
4
was low in spring and high in summer, for all three vertical layers. In addition, there was a peak of CH
4
in winter near the ground, both in the troposphere and the whole atmosphere. We found that variation of CH
4
in the tropospheric column was close to that of the in-situ measurements near the ground. Furthermore, the variations of CH
4
in the stratospheric column could be influenced by vertical motions, since it was higher in summer and lower in winter.
Pleckstrin-2 is a member of pleckstrin family with well-defined structural features that was first identified in 1999. Over the past 20 years, our understanding of PLEK2 biology has been limited to ...cell spreading. Recently, increasing evidences support that PLEK2 plays important roles in other cellular events beyond cell spreading, such as erythropoiesis, tumorigenesis and metastasis. It serves as a potential diagnostic and prognostic biomarker as well as an attractive target for the treatment of cancers. Herein, we summary the protein structure and molecular interactions of pleckstrin-2, with an emphasis on its regulatory roles in tumorigenesis.
In recent years, the exploration of seabed has been intensified, but the submarine soils of silt and sand in the Yellow Sea area have not been well investigated so far. In this study, the physical ...and mechanical properties of silt and sand from the Yellow Sea were measured using a direct shear apparatus and their microstructures were observed using a scanning electron microscope. The test results suggest that the shear strength of silt and sand increases linearly with the increase of normal stress. Based on the direct shear test, the scanning electron microscope was used to observe the section surface of sand. It is observed that the section surface becomes rough, with many “V”‐shaped cracks. Many particles appear on the surface of the silt structure and tend to be disintegrated. The X‐ray diffraction experiment reveals that the sand and silt have different compositions. The shear strength of sand is slightly greater than that of silt under high stress, which is related to the shape of soil particles and the mineral composition. These results can be a reference for further study of other soils in the Yellow Sea; meanwhile, they can serve as soil parameters for the stability and durability analyses of offshore infrastructure construction.
In this study, the physical and mechanical properties of silt and sand from the Yellow Sea are measured and microscopically explored.
Highlights
The physical and mechanical properties of silt and sand from the Yellow Sea are measured and microscopically explored.
After the direct shear test, it is found that the section surface of sand becomes rough, with many “V”‐shaped cracks. Many particles of the silt structure appear on the surface and tend to disintegrate.
The X‐ray diffraction experiment reveals that the compositions of sandy and silty soils are different.
In order to investigate the diurnal, seasonal, and inter-annual variations of nitrous oxide (N2O) flux and associated microbiological mechanisms, in situ measurements of N2O Flux from unfertilized, ...ungrazed, and unirrigated semi-arid grassland soils in Inner Mongolia, northeast China were undertaken using a closed chamber technique from 1995 to 2003. In addition, laboratory experiments were carried out using the acetylene inhibition method (AIM) in 1998 and 2001. The results showed no significant linear relationship between soil moisture and diurnal N2O flux, or between N2O flux and temperature (i.e., temperature at 0-15 cm depth, temperature of surface soil, and temperature of inner chamber air). However, the results showed a significant influence of growing season on diurnal variations of N2O flux. N2O efflux was usually high in spring or summer, and low in winter. The mean total annual N2O fluxes was 0.73±0.52 kg N2O-N ha-1 yr-1, with a coefficient of variation of annual N2O flux of 71.6%. Based on our estimates from 5 yr of data, the total N2O emission from all of the temperate grassland soils of China was approximately 0.21 Tg N2O-N yr-1, which was about 21% of the total global flux from temperate grassland soils. It was the distribution of effective rainfall, rather than precipitation intensity, that influenced seasonal and inter-annual variations of N2O flux. Our laboratory incubation study revealed that heterotrophic nitrification was the principal source of N2O in the studied soils.
Terahertz imaging technology has shown great potential in many fields. As the core component of terahertz imaging systems, terahertz detectors have received extensive attention. In this paper, a ...metasurface-based terahertz optomechanical detector is proposed, which is made of two fabrication-friendly materials: gold and silicon nitride. The optomechanical detector is essentially a thermal detector composed of metasurface absorber, bi-material micro-cantilevers and heat insulation pillars. Compared with traditional thermal terahertz detectors, the optomechanical detector employs a metasurface absorber as the terahertz radiation coupler and obtains an absorptivity higher than 90% from 3.24 to 3.98 THz, which is much higher than that of traditional terahertz detectors with absorbers made from natural materials. Furthermore, the detector is fabricated by MEMS process and its responsivity has been verified by a specifically designed optical read-out system; the measured optomechanical responsivity is 24.8 μm/μW, which agrees well with the multi-physics simulation. These results indicated that the detector can be employed as a pixel to form a terahertz focal plane array in the future, and further realize real-time terahertz imaging at room temperature.
This study sought to analyze the main antibacterial active components of Lactobacillus pentosus (L. pentosus) L-36 cell-free culture supernatants (CFCS) in inhibiting the growth of Staphylococcus ...aureus (S. aureus), to explore its physicochemical properties and anti-bacterial mechanism. Firstly, the main antibacterial active substance in L-36 CFCS was peptides, which inferred by adjusting pH and enzyme treatment methods. Secondly, the physicochemical properties of the antibacterial active substances in L-36 CFCS were studied from heat, pH, and metal ions, respectively. It demonstrated good antibacterial activity when heated at 65 °C, 85 °C and 100 °C for 10 and 30 min, indicating that it had strong thermal stability. L-36 CFCS had antibacterial activity when the pH value was 2-6, and the antibacterial active substances became stable with the decrease in pH value. After 10 kinds of metal ions were treated, the antibacterial activity did not change significantly, indicating that it was insensitive to metal ions. Finally, scanning electron microscopy, transmission electron microscopy and fluorescence probe were used to reveal the antibacterial mechanism of S. aureus from the aspects of cell morphology and subcellular structure. The results demonstrated that L-36 CFCS could form 1.4-2.3 nm pores in the cell membrane of S. aureus, which increased the permeability of the bacterial cell membrane, resulting in the depolarization of cell membrane potential and leakage of nucleic acid protein and other cell contents. Meanwhile, a large number of ROS are produced and accumulated in the cells, causing damage to DNA, and with the increase in L-36 CFCS concentration, the effect is enhanced, and finally leads to the death of S. aureus. Our study suggests that the main antibacterial active substances of L-36 CFCS are peptides. L-36 CFCS are thermostable, active under acidic conditions, insensitive to metal ions, and exhibit antibacterial effects by damaging cell membranes, DNA and increasing ROS. Using lactic acid bacteria to inhibit S. aureus provides a theoretical basis for the discovery of new antibacterial substances, and will have great significance in the development of antibiotic substitutes, reducing bacterial resistance and ensuring animal food safety.
A comparative study was carried out to explore carbon monoxide total columnar amount (CO TC) in background and polluted atmosphere, including the stations of ZSS (Zvenigorod), ZOTTO (Central ...Siberia), Peterhof, Beijing, and Moscow, during 1998–2014, on the basis of ground- and satellite-based spectroscopic measurements. Interannual variations of CO TC in different regions of Eurasia were obtained from ground-based spectroscopic observations, combined with satellite data from the sensors MOPITT (2001–14), AIRS (2003–14), and IASI MetOp-A (2010–13). A decreasing trend in CO TC (1998–2014) was found at the urban site of Beijing, where CO TC decreased by 1.14%±0.87% yr
−1
. Meanwhile, at the Moscow site, CO TC decreased remarkably by 3.73%±0.39% yr
−1
. In the background regions (ZSS, ZOTTO, Peterhof), the reduction was 0.9%–1.7% yr
−1
during the same period. Based on the AIRSv6 satellite data for the period 2003–14, a slight decrease (0.4%–0.6% yr
−1
) of CO TC was detected over the midlatitudes of Eurasia, while a reduction of 0.9%–1.2% yr
−1
was found in Southeast Asia. The degree of correlation between the CO TC derived from satellite products (MOPITTv6 Joint, AIRSv6 and IASI MetOp-A) and ground-based measurements was calculated, revealing significant correlation in unpolluted regions. While in polluted areas, IASI MetOp-A and AIRSv6 data underestimated CO TC by a factor of 1.5–2.8. On average, the correlation coefficient between ground- and satellite-based data increased significantly for cases with PBL heights greater than 500 m.
The measurements of soot aerosol concentration in Moscow and Beijing in 2004–2010 are presented. The variability ranges of one-time soot concentrations in this period of time had been 0.1–77 μg/m
3
...in Beijing and 0.1–22 μg/m
3
in Moscow. The seven-year average daytime soot concentration in Beijing is 2.5 times higher than in Moscow. The seasonal behavior of the soot concentration is more pronounced in Moscow: the soot concentration is 33% lower in summer than in winter, and only 13% lower in Beijing. Analysis of back trajectories of air mass transport and variations in soot concentration showed that the soot content in the atmosphere of Beijing significantly increases when air masses are transported from industrially developed regions south of Beijing. The air pollution by soot in Moscow predominantly decreases due to advection when air masses from northern regions come to Moscow.
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