Enhanced chromium and nitrogen removal by constructing a biofilm reaction system based on denitrifying bacteria preferential colonization theory.

Understanding the developmental characteristics of microbial communities in biofilms is crucial for designing targeted functional microbial enhancements for the remediation of complex contamination scenarios. The strong prioritization effect of microorganisms confers the ability to colonize strains that arrive first dominantly. In this study, the auto-aggregating denitrifying bacterial Pseudomonas stutzeri strain YC-34, which has both nitrogen and chromium removal characteristics, was used as a biological material to form a stable biofilm system based on the principle of dominant colonization and biofortification. The effect of the biofilm system on nitrogen and chromium removal was characterized by measuring the changes in the quality of influent and effluent water. The pattern of biofilm changes was analyzed by measuring biofilm content and thickness and characterizing extracellular polymer substances (EPS). Further analysis of the biofilm microbiota characteristics and potential functions revealed the mechanism of strain YC-34 biofortified biofilm. The results revealed that the biofilm system formed could achieve 90.56% nitrate-nitrogen removal with an average initial nitrate-nitrogen concentration of 51.9 mg/L and 40% chromium removal with an average initial hexavalent chromium Cr(VI) concentration of 7.12 mg/L. The biofilm properties of the system were comparatively analyzed during the biofilm formation period, the fluctuation period of Cr(VI)-stressed water quality, and the stabilization period of Cr(VI)-stressed water quality. The biofilm system may be able to increase the structure of hydrogen bonds, the type of protein secondary structure, and the abundance of amino acid-like components in the EPS, which may confer biofilm tolerance to Cr(VI) stress and allow the system to maintain a stable biofilm structure. Furthermore, microbial characterization indicated an increase in microbial diversity in the face of chromium stress, with an increase in the abundance of nitrogen removal-associated functional microbiota and an increasing trend in the abundance of nitrogen transfer pathways. These results demonstrate that the biofilm system is stable in nitrogen and chromium removal. This bioaugmentation method may provide a new way for the remediation of heavy metal-polluted water bodies and also provides theoretical and application parameters for the popularization and application of biofilm systems.

Nitrogen removal intensification of biofilm through bioaugmentation with Methylobacterium gregans DC-1 during wastewater treatment.

The increasing concern for environmental remediation has led to a search for effective methods to remove eutrophic nutrients. In this study, Methylobacterium gregans DC-1 was utilized to improve nitrogen removal in a sequencing batch biofilm reactor (SBBR) via aerobic denitrification. This bacterium has the extraordinary characteristics of strong auto-aggregation and a high ability to remove nitrogen efficiently, making it an ideal candidate for enhanced treatment of nitrogen-rich wastewater. This strain was used for the bioassessment of a test reactor (SBBRbio), which showed a shorter biofilm formation time compared to a control reactor (SBBRcon) without this strain inoculation. Moreover, the enhanced biofilm was enriched in TB-EPS and had a wider variety of protein secondary structures than SBBRcon. During the stabilization phase of SBBRbio, the EPS molecules showed the highest proportion of intermolecular hydrogen bonding. It is possible that bioaugmentation with this strain positively affects the structural stability of biofilm. At influent ammonia loadings of 100 and 150 mg. L-1, the average reduction of ammonia and nitrate-nitrogen was higher in the experimental system compared to the control system. Additionally, nitrite-N accumulation was lower and N2O production decreased compared to the control. Analysis of the microbial community structure demonstrated successful colonization in the bioreactor by a highly nitrogen-tolerant strain that efficiently removed inorganic nitrogen. These results illustrate the great potential of this type of denitrifying bacteria in the application of bioaugmentation systems.

Systematic investigation of simultaneous copper biosorption and nitrogen removal from wastewater by an aerobic denitrifying bacterium of auto-aggregation.

Finding effective methods for simultaneous removal of eutrophic nutrients and heavy metals has attracted increasing concerns for the environmental remediation. Herein, a novel auto-aggregating aerobic denitrifying strain (Aeromonas veronii YL-41) was isolated with capacities for copper tolerance and biosorption. The denitrification efficiency and nitrogen removal pathway of the strain were investigated by nitrogen balance analysis and amplification of key denitrification functional genes. Moreover, the changes in the auto-aggregation properties of the strain caused by extracellular polymeric substances (EPS) production were focused on. The biosorption capacity and mechanisms of copper tolerance during denitrification were further explored by measuring changes in copper tolerance and adsorption indices, as well as by variations in extracellular functional groups. The strain showed extremely strong total nitrogen removal ability, with 67.5%, 82.08% and 78.48% of total nitrogen removal when NH4+-N, NO2--N, and NO3--N were used as the only initial nitrogen source, respectively. The successful amplification of napA, nirK, norR, and nosZ genes further demonstrated that the strain accomplished nitrate removal through a complete aerobic denitrification pathway. The production of protein-rich EPS of up to 23.31 mg/g and an auto-aggregation index of up to 76.42% may confer a strong biofilm-forming potential to the strain. Under the stress of 20 mg/L copper ions, the removal of nitrate-nitrogen was still as high as 71.4%. In addition, the strain could achieve an efficient removal of 96.9% of copper ions at an initial concentration of 80 mg/L. Scanning electron microscopy and deconvolution analysis of characteristic peaks confirmed that the strains encapsulate heavy metals by secreting EPS and, meanwhile, form strong hydrogen bonding structures to enhance intermolecular forces to resist copper ion stress. This study provides an innovative and effective biological approach for the synergistic bioaugmentation removal of eutrophic substances and heavy metals from aquatic environments.

The Quadratic Constitutive Model Based on Partial Derivative and Taylor Series of Ti6242s Alloy and Predictability Analysis.

To solve the problem of insufficient predictability in the classical models for the Ti6242s alloy, a new constitutive model was proposed, based on the partial derivatives from experimental data and the Taylor series. Firstly, hot compression experiments on the Ti6242s alloy at different temperatures and different strain rates were carried out, and the Arrhenius model and Hensel-Spittel model were constructed. Secondly, the partial derivatives of logarithmic stress with respect to temperature and logarithmic strain rate at low, medium and high strain levels were analyzed. Thirdly, two new constitutive models with first- and second-order approximation were proposed to meet the requirements of high precision. In this new model, by analyzing the high-order differential data of experimental data and combining the Taylor series theory, the minimum number of terms that can accurately approximate the experimental rheological data was found, thereby achieving an accurate prediction of flow stress with minimal material parameters. In the new model, by analyzing the high-order differential of the experimental data and combining the theory of the Taylor series, the minimum number of terms that can accurately approximate the experimental rheological data was found, thereby achieving an accurate prediction of flow stress with minimal material parameters. Finally, the prediction accuracies for the classical model and the new model were compared, and the predictabilities for the classical models and the new model were proved by mathematical means. The results show that the prediction accuracies of the Arrhenius model and the Hensel-Spittel model are low in the single-phase region and high in the two-phase region. In addition, second-order approximation is required between the logarithmic stress and logarithmic strain rate, and first-order approximation is required between logarithmic stress and temperature to establish a high-precision model. The order of prediction accuracy of the four models from high to low is the quadratic model, Arrhenius model, linear model and HS model. The prediction accuracy of the quadratic model in all temperatures and strain rates had no significant difference, and was higher than the other models. The quadratic model can greatly improve prediction accuracy without significantly increasing the material parameters.

Evaluation of Four Commonly Used DNA Barcoding Loci for Ardisia Species Identification.

Ardisia plants have been used as medicinal plants for a long time in China. Traditional techniques such as morphological, microscopic, and chemical identification methods all have limitations in the species identification of Ardisia. For the sake of drug safety, four DNA barcodes (psbA-trnH, ITS, rbcL, and matK) were assessed for Chinese Ardisia plants using a total of 121 individuals from 33 species. Four criteria (The success rates of PCR amplification, DNA barcoding gap, DNA sequence similarity analysis and NJ tree clustering analysis) were used to evaluate the species identification ability of these four DNA barcodes. The results show that ITS had the highest efficiency in terms of PCR and sequencing and exhibited the most apparent inter- and intra-specific divergences and the highest species identification efficiency. There was no significant increase in species identification after combining the three cpDNA fragments with the ITS fragment. Considering the cost and experimental effectiveness, we recommend ITS as the core barcode for identifying Chinese Ardisia plants.

Enhanced North Pacific subtropical gyre circulation during the late Holocene.

The North Pacific Subtropical Gyre circulation redistributes heat from the Western Pacific Warm Pool towards the mid- to high-latitude North Pacific. However, the driving mechanisms of this circulation and how it changed over the Holocene remain poorly understood. Here, we present alkenone-based sea surface temperature reconstructions along the Kuroshio, California and Alaska currents that cover the past ~7,000 years. These and other paleorecords collectively demonstrate a coherent intensification of the boundary currents, and thereby the basin-scale subtropical gyre circulation, since ~3,000-4,000 years ago. Such enhanced circulation during the late Holocene appears to have resulted from a long-term southward migration of the Intertropical Convergence Zone, associated with Holocene ocean cooling. Our results imply that the North Pacific Subtropical Gyre circulation could be weakened under future global warming.

The complete chloroplast genome of Callicarpa integerrima var. chinensis (Lamiaceae) from Guilin, China, a potential medicinal plant.

Callicarpa integerrima var. chinensis is one of the traditional medical herbs which has the potential for multiple diseases' treatment. In this study, the complete chloroplast genome sequence of C. integerrima var. chinensis was sequenced and assembled. A typical quadripartite structure was observed in the chloroplast genome of C. integerrima var. chinensis which was 154179 bp in length, including a pair of inverted repeat (IR) regions (each 51396 bp) separated by a large single-copy region (LSC) of 84927 bp and a small single-copy region (SSC) of 17856 bp, and the overall GC contents of the chloroplast genome was 38.08%. Additionally, we annotated 132 genes, including 86 protein-coding genes, 38 tRNA genes, and 8 rRNA genes. Phylogenetic analysis was adopted which confirmed the position of C. integerrima var. chinensis was close to the congeneric C. formosana and C. siongsaiensis.

Characterization of the complete chloroplast genome of Rohdea wattii (Asparagaceae).

As a kind of rare plant with important medicinal value and breeding value, Rohdea wattii usually grow in dark and damp places. In this study, we reported the complete chloroplast genome of R. wattii. We used a variety of bioinformatics analysis methods to analyze and visualize the chloroplast genome and phylogenetic relationships. A typical quadripartite structure was observed in the chloroplast genome of R. wattii with a genome size of 156,487 bp. The length of the large single-copy region (LSC) was 84,969 bp, which was the longest region among the four regions; the second longest was the Inverted repeat region (IR) with 26,451 bp in length; and the smallest was the small single-copy region (SSC) with 18,616 bp in length. The overall GC content of R. wattii chloroplast genome is 37.61%. In addition, a total of 132 genes were identified in the whole genome of R. wattii, which include 86 protein-coding genes, 38 tRNA genes, and eight rRNA genes. Finally, by constructing a phylogenetic tree to analyze the phylogeny of R. wattii, and it indicated that R. wattii and Rohdea chinensis are a close evolutionary relationship.

The complete chloroplast genome of Euphorbia hirta (Euphorbiaceae), a commonly used medicinal plant in China.

Plants in the genus Euphorbia have been widely used as herbal medicine, and for ornamental horticulture and biofuel production. In this study, we report the complete chloroplast genome of Euphorbia hirta which is known as the 'asthma-plant' due to its medicinal use. The chloroplast genome of this species is 164,340 bp in length, including a pair of inverted repeat regions (IRs) (27,354 bp) that are divided by a large single-copy region (LSC) (91,373 bp) and a small single-copy region (SSC) (18,259 bp). The chloroplast genome of E. hirta contains 111 unique genes (77 protein-coding, 30 tRNA, and four rRNA), 19 of which are duplicated in the IR regions. The overall GC content is 35.4%. Phylogenetic analysis fully resolved E. hirta groups with other species of Euphorbia. The complete chloroplast genome of E. hirta provides useful information that can be used to distinguish related species and reconstruct evolutionary relationships.

Characteristics of pain sensitivity in children and model mice with autism spectrum disorder disorders / 中国学校卫生

Objective@#To explore the characteristics of pain sensitivity of autism spectrum disorder (ASD), and to provide reference for clinical comprehensive intervention of ASD.@*Methods@#A case-control study was conducted to investigate the characteristics of pain sensitivity in 142 ASD children and 142 normal children using the items related to pain sensitivity in the Autism Treatment Evaluation Checklist (ATEC). In addition, two recognized ASD model mice (BTBR mice and model mice induced by VPA) were selected as experimental group. The thermal pain threshold and mechanical pain threshold of BTBR mice were measured by electroshock seizure threshold and Von Frey filament test, and the differences of pain characteristics between BTBR mice and control mice were compared, the thermal pain threshold of model mice induced by VPA (VPA rats) was measured by electroshock seizure threshold, and the differences between BTBR mice and control mice (Con) were compared.@*Results@#There was significant difference in pain sensitivity between ASD group and control group (χ 2=0.81，P<0.05), and the sensitivity of ASD children to pain was significantly lower than that of normal control children. The pain sensitivity of BTBR mice and C57BL/6 mice on the 42 nd day after birth was measured. The T-test analysis showed that the time taken for BTBR and C57BL/6 mice to retract their feet on the 42 nd day after birth (3.62±0.38,3.02±0.33)s (t=3.28,P<0.01), and the mechanical pain threshold (9.75±3.58,0.55±0.93)s (t=7.44,P<0.01). The detection of thermal stinging pain in VPA rats and con rats on the 9 th, 11 th, 13 th and 15 th day after birth was detected. The results of t test were as follows:P9(11.34±1.38,9.81±1.64)g, P11(11.37±1.98,9.36±1.11)g, P13(11.53±1.38,9.51±1.01)g and P15(12.05±2.91,8.74±1.60)g (t=-2.79,-2.25,3.95,3.95,P<0.05).@*Conclusion@#Compared with normal control children, ASD children show insensitivity to pain which is further supported by two types of animal models for ASD.

Equatorial Pacific forcing of western Amazonian precipitation during Heinrich Stadial 1.

Abundant hydroclimatic evidence from western Amazonia and the adjacent Andes documents wet conditions during Heinrich Stadial 1 (HS1, 18-15 ka), a cold period in the high latitudes of the North Atlantic. This precipitation anomaly was attributed to a strengthening of the South American summer monsoon due to a change in the Atlantic interhemispheric sea surface temperature (SST) gradient. However, the physical viability of this mechanism has never been rigorously tested. We address this issue by combining a thorough compilation of tropical South American paleorecords and a set of atmosphere model sensitivity experiments. Our results show that the Atlantic SST variations alone, although leading to dry conditions in northern South America and wet conditions in northeastern Brazil, cannot produce increased precipitation over western Amazonia and the adjacent Andes during HS1. Instead, an eastern equatorial Pacific SST increase (i.e., 0.5-1.5 °C), in response to the slowdown of the Atlantic Meridional Overturning Circulation during HS1, is crucial to generate the wet conditions in these regions. The mechanism works via anomalous low sea level pressure over the eastern equatorial Pacific, which promotes a regional easterly low-level wind anomaly and moisture recycling from central Amazonia towards the Andes.