Complete genome sequence of Roseivivax marinus strain TCYB24 with quorum sensing system reveal the adaptive mechanism against deep-sea hydrothermal environment.

Roseivivax marinus strain TCYB24 is a rod-shaped bacterium of Rhodobacteraceae isolated from the gill of deep-sea mussel Bathymodiolus marisindicus which collected from the Tiancheng hydrothermal vent under depth of 2700 m on the southwest Indian ridge. In our previous study, the strain TCYB24 was proved to produce quorum sensing signal of N-Acyl-homoserine lactones (AHLs) and form biofilm. In order to determine its adaptive mechanism against the extreme environment of deep-sea hydrothermal vents, the whole genome was sequenced by high-throughput Illumina tag sequencing. The results show the whole genome consists of one circular chromosome and eight circular plasmids, with a total length of 4.60 Mb (G + C content of 67.4%), 4338 open reading frames, 46 tRNAs and 6 rRNA operons. According to the genome-wide functional annotation, numbers of heavy metal resistance, high pressure and cold adapting related genes were found. In addition, genes about exopolysaccharide (EPS) biosynthesis and secretion and biofilm formation, which facilitate bacteria to resist extreme environments, were identified. Intriguingly, a pair of RaiI/R-type quorum sensing system was discovered firstly in the bacterium isolated from hydrothermal environment. The results may help to understand genetic underpinning of extreme environmental adaptation mechanism of bacteria in deep-sea hydrothermal area.

[Responses mechanism of C:N:P stoichiometry of soil microbial biomass and soil enzymes to climate change.] / åœŸå£¤å¾®ç”Ÿç‰©ç”Ÿç‰©é‡ç¢³æ°®ç£·ä¸ŽåœŸå£¤é ¶åŒ–å­¦è®¡é‡å¯¹æ°”å€™å˜åŒ–çš„å“åº”æœºåˆ¶.

Microorganisms and soil enzymes are important drivers for biogeochemical cycles in terrestrial ecosystems. Understanding the role of microorganisms in the regulation of ecosystems and the response mechanisms of microbial biomass and soil enzymes to climate change are important topic in ecology. From the perspective of climatic factors, this review introduced the roles of microorganisms and soil enzymes in the carbon, nitrogen and phosphorus cycles of terrestrial ecosystems based on the theory of ecological stoichiometry. Moreover, we synthesized the responses mechanisms of soil microbial and soil enzyme stoichiometry, i.e., changes of microbial metabolic rate, enzymatic acti-vity, microbial community structure, ecological stoichiometry of soil microbial biomass and soil enzymes, and nutrient use efficiency. Finally, we analyzed the current research inadequacies and proposed the scientific problems in this field, i.e., to comprehensively elucidate the response mecha-nism of soil microbes and soil enzymes to climate change; to examine the nutrient coupling mechanism of soil microbes and extracellular enzymes; and to explore the adaptive strategies of C:N:P stoichiometry of soil microbial biomass and soil enzymes to climate change.

[Population spatial patterns of grassland plant communities in different slope aspects in the loess hilly area, China.] / é»„åœŸä¸˜é™µæ²Ÿå£‘åŒºä¸åŒå¡å‘æ’‚è’è‰åœ°æ¤ç‰©ç¾¤è½ç§ç¾¤ç©ºé—´æ ¼å±€.

We investigated the species composition and diversity of four grassland communities with different slope aspects in the loess hilly area of China. The power law was used to analyze spatial heterogeneity of the community and spatial pattern of the population. The results showed that Artemisia sacrorum was the dominant species and occurred in each site. Other species had different status and contributed differently to the spatial pattern of communities. Moreover, the spatial patterns of communities responded differently to various slope aspects, with the degree of aggregation ranked as sunny > half-sunny > half-shady > shady. The spatial heterogeneity index of community was positively correlated with the Simpson diversity index, but was negatively correlated with Margalef richness, Shannon diversity and Pielou evenness. The relative spatial heterogeneity index of the dominant species (A. sacrorum), sub-dominant species (Lespedeza dahurica and Stipa bungeana), and a few associated species (Artemisia scoparia, Melica scabrosa) were larger than that of the community, which resulted in cluster distribution. However, the relative spatial heterogeneity index of most associated species (Phragmites communis, Sonchus arvensis, and Bothriochloa flaccidum) showed the similar trends with the distribution of the community. In contrast, the relative spatial heterogeneity index of Cephalanoplos segetum, Gueldenstaedtia multiflora and Artemisia giraldii was lower than that of the community. These differences reduced the aggregation degree of the community. In summary, the aggregation degree of community was determined by dominant species, sub-dominant species and occasional species. Specifically, the dominant species, sub-dominant species and some associated species could promote the aggregation of the community, but occasional species would reduce the cluster distribution.

[Relationship Between the Vegetation Community and Soil Nutrient and Enzyme Activity During the Restoration of Abandoned Land in the Loess Hilly Region].

The trends of and relationships among the plant community, soil nutrients, and four soil enzymes were investigated after being abandoned for 10, 15, 20, 30, and 45 years to reveal the soil properties during the restoration in the Loess Hilly Region. The results indicate the following ranking of dominant plant community species:Artemisia scoparia→Lespedeza dahurica+Artemisia sacrorum→Artemisia giraldii+irons Artemisia annua→Bothriochloa flaccidum+Artemisia selengensis. The ranking reflects an increase along the chronosequence of abandoned land. Moreover, the ratio of the total species of Compositae, Poaceae, and Leguminosae decreases from 66.67% to 50% and then increases up to 75%. The SOC, TN, TP, AN, AP, and four enzyme activity types (ALP, CAT, UE, and SC) increase but respond differently to restoration, while the stoichiometric ratio fluctuates. In contrast to the number of plant families, genus, species, and plant diversity, Compositae, Poaceae, and Leguminosae have major effects on the soil nutrient and enzyme activity, which explains the total variation of 72.8%, 69.1%, and 66.0%, respectively. The effects of these three families on the soil enzymes are greater than that on soil nutrients. Poaceae and Leguminosae have a positive effect on the nutrient and enzyme activity, while the family Compositae has a negative effect. Overall, the changes of dominant species of grassland communities during restoration significantly affect the soil enzyme and thereby are responsible for the soil nutrient dynamics.

Gate leakage current induced trapping in AlGaN/GaN Schottky-gate HFETs and MISHFETs.

This study examined the correlation between the off-state leakage current and dynamic on-resistance (RON) transients in AlGaN/GaN heterostructure field-effect transistors (HFETs) with and without a gate insulator under various stress conditions. The RON transients in a Schottky-gate HFET (SGHFET) and metal-insulator-semiconductor HFET (MISHFET) were observed after applying various amounts of drain-source bias stress. The gate insulator in the MISHFET effectively reduced the electron injection from the gate, thereby mitigating the degradation in dynamic switching performance. However, at relaxation times exceeding 10 ms, additional detrapping occurred in both the SGHFET and MISHFET when the applied stress exceeded a critical voltage level, 50 V for the SGHFET and 60 V for MISHFET, resulting in resistive leakage current build-up and the formation of hot carriers. These high-energy carriers acted as ionized traps in the channel or buffer layers, which subsequently caused additional trapping and detrapping to occur in both HFETs during the dynamic switching test conducted.

Calcium-binding capacity of wheat germ protein hydrolysate and characterization of Peptide-calcium complex.

This study investigates the ability of various wheat germ protein hydrolysates (WGPHs) to bind calcium and characterizes the peptide-calcium complexes. We demonstrate that the amount of Ca bound depended greatly on the type of enzyme, degree of hydrolysis (DH), amino acid composition, and molecular mass distribution of different hydrolysates. The maximum level of Ca bound (67.5 mg·g(-1)) occurred when Alcalase was used to hydrolyze wheat germ protein at a DH of 21.5%. Peptide fragments exhibiting high calcium-binding capacity had molecular mass <2000 Da. The calcium-binding peptides mainly consisted of Glu, Arg, Asp, and Gly, and the level of Ca bound was related to the hydrophobic amino acid content in WGPHs. UV-visible and Fourier transform infrared spectra demonstrate that amino nitrogen atoms and oxygen atoms on the carboxyl group were involved in complexation. Therefore, wheat germ protein is a promising protein source for the production of calcium-binding peptides and could be utilized as a bioactive ingredient for nutraceutical food production.

Effect of water migration between arabinoxylans and gluten on baking quality of whole wheat bread detected by magnetic resonance imaging (MRI).

A new method, a magnetic resonance imaging (MRI) technique characterized by T(2) relaxation time, was developed to study the water migration mechanism between arabinoxylan (AX) gels and gluten matrix in a whole wheat dough (WWD) system prepared from whole wheat flour (WWF) of different particle sizes. The water sequestration of AX gels in wheat bran was verified by the bran fortification test. The evaluations of baking quality of whole wheat bread (WWB) made from WWF with different particle sizes were performed by using SEM, FT-IR, and RP-HPLC techniques. Results showed that the WWB made from WWF of average particle size of 96.99 µm had better baking quality than those of the breads made from WWF of two other particle sizes, 50.21 and 235.40 µm. T(2) relaxation time testing indicated that the decreased particle size of WWF increased the water absorption of AX gels, which led to water migration from the gluten network to the AX gels and resulted in inferior baking quality of WWB.

Preparation of chitosan oligomers COS and their effect on the retrogradation of intermediate amylose rice starch.

Chitosan oligomers (COS) were obtained by enzymatic hydrolysis and H2O2 oxidative treatment, and then separated into different fractions using ultra-filtration membranes. Each COSM fraction prepared using enzymatic hydrolysis retained its structure, especially the reduced end residue (-NH2 group), and had a peak for molecular weight. On the other hand, each COSH fraction prepared by oxidative treatment had partly damaged -NH2 groups and two peaks for molecular weight. These results indicate that the same COS fractions prepared by the two methods differ in their amino groups and in their molecular weights, though they can both pass through the same size ultra-filtration membrane. The effect of COS on the retrogradation of intermediate amylose rice starch (IA-RS) was also investigated. The 5 k < COSM < 10 k fraction had the best anti-retrogradation ability; the retrogradation ratio of IA-RS with this fraction was reduced by 14.5%, compared to the control, and its relative crystallinity was only 59.69%. 10 k < COSM < 30 k fraction was second best, while the COSM < 5 k fraction had no effect. Therefore, the molecular size of COS determined its anti-retrogradation capability. All COSH fractions from oxidative treatment had no effect on the retrogradation.

Inactivation of soybean lipoxygenase in soymilk by pulsed electric fields.

The inactivation of soybean lipoxygenase by pulsed electric fields (PEF) was studied. Effects of PEF parameters (treatment time, pulse strength, pulse frequency and pulse width) were evaluated. Soymilk was exposed to pulsed strengths from 20 to 42kV/cm for up to 1036µs treatment time in square wave pulse of bipolar mode. Moreover, pulse frequency (100-600Hz) and pulse width (1-5µs) was also tested at constant pulsed treatment time of 345µs and strength of 30kV/cm. Residual activity of soybean lipoxygenase decreased with the increase of treatment time, pulse strength, pulse frequency and pulse width. The maximum inactivation of soybean lipoxygenase by PEF achieved 88% at 42kV/cm for 1036µs with 400Hz of pulse frequency and 2µs of pulse width at 25°C. Inactivation of soybean lipoxygenase by pulsed electric fields was modeled using several kinetic models. Weibull distribution function was most suitable model describing the inactivation of soybean LOX as a function of pulsed electric fields process parameters. Moreover, reduction of soybean LOX activity related to the electric field strength could be well described by the Fermi model.

Schwann cell apoptosis in Wallerian-degenerated sciatic nerve of the rat.

OBJECTIVE: To investigate systematically Schwann cell apoptosis in Wallerian-degenerated sciatic nerve of the rat, and evaluate its time-related feature. METHODS: Ninety-five SD rats were divided randomly into one normal group (8 rats) and 11 experimental groups (66 rats, 6 in each). Both hind legs of each rat in experimental groups were randomly divided into test leg (sciatic nerve transected) and control one (nerve uninjured). All test legs constituted a test group and all control legs constituted a control one. After operation, all rats were respectively sacrificed at 1 h, 6 h, 12 h, 24 h, 2 d, 3 d, 4 d, 8 d, 14 d, 21 d, and 30 d. We analyzed the specimens of mid-distal sciatic nerve, especially the morphological changes of the nerve, the different expression levels of S-100 protein and apoptosis-related proteins such as Bcl-2, Bax, and Fas in Schwann cells. The TUNEL method was used to detect the apoptotic rate of Schwann cells. RESULTS: (1) The test group showed Wallerian degeneration. The number of Schwann cells began to decrease at 24 h, obviously decreased on day 3 and 4, then began to increase from day 8 and formed Bungner belt after 14 days. (2) Schwann cells generally expressed S-100 at a low level in all groups. The control group was not significantly different from the normal group. The test group had statistical significance at 1 h and day 21. (3) As an inhibitory gene protein of Schwann cell apoptosis, Bcl-2 positive rates in the control and test groups apparently elevated and were statistically different from the normal group. (4) As a promotive gene protein of Schwann cell apoptosis, the control and test groups expressed Bax at a high level and were statistically different from the normal group. (5) As a promotive gene protein of Schwann cell apoptosis, Fas positive rate in control group was slightly elevated, but had no statistical significance compared with the normal group. Fas positive rate in test group continuously elevated in a fluctuant way, with highly statistical significance compared with the normal group. (6) TUNEL detection further proved that Schwann cell apoptosis rarely existed in the normal group, and the left sciatic nerve had no statistical significance compared with the right sciatic nerve. While the test group showed lots of apoptotic nuclei at 6 h, 2 d, 4 d, and 21 d. It had highly statistical significance compared with the normal group. CONCLUSIONS: Schwann cell apoptosis does exist in Wallerian-degenerated sciatic nerve of the rat after transection. Schwann cell apoptosis and its apoptotic genes expression have a time-related feature.