Ecological risk threshold for chromium in Chinese soils and its prediction models.

The derivation of chromium (Cr) ecological risk thresholds in soils remains limited, despite their importance as measurement standards and indicators for enacting soil protection policies. In this study, toxicity of Cr in soil to different species was tested based on Log-Logistic dose-effect relationship. On this basis, combined with Cr toxicity measurement data in literature, the ecological risk threshold HC5 for protecting 95% species safety in soils with different properties was obtained by fitting species sensitivity distribution curve (SSD). This research collected various Cr toxicological data from Chinese cropland soils, based on 31 different endpoints covering soil fauna, functional indicators of microorganisms, terrestrial plants, etc., sourced from both our laboratory and existing literature. We applied the SSD method to estimate the hazardous concentration of Cr for HC5 and ultimately established a predictive model according to HC5 and different soil properties. As a result, the EC10 (an effective concentration of Cr resulting in 10% suppression of terminal biological activity) based on 7 different soils and 4 endpoints ranged from 16.8 to 148.0 mg kg-1, and the hormesis of Cr induction reached up to 109%. Overall, the toxicity (EC10) to microorganisms was much lower, while it was higher for graminoids. All the toxicity data were corrected through an aging factor with up to 540 days of equilibration before fitting the SSD curves. After that, a prediction model considering HC5 values and soil properties was established as LogHC5 = 3.003LogpH +0.651LogOC +0.013LogCEC - 0.476. The model was well-verified in field experiments, as the actual and predicted values fell within a 2-fold error range. This approach offers a rigorous scientific foundation for determining the Cr ecological risk threshold and could be important for the conservation of ecological species in soils.

The environmental risk threshold (HC5) for Cd remediation in Chinese agricultural soils.

Given the increasing concern over Cd contamination of agricultural soils in China, reducing the availability of the toxic metal has become an important remedial strategy. However, the lack of a unified evaluation framework complicates the assessment of remediation efficiency of different practices. Here, we evaluated the general extraction method (GEM) of available Cd in nine typical soil types by comparing extraction agents, including CaCl2, EDTA, Mehlich-Ⅲ, HCl and DTPA. The safe grain concentration of different agricultural products from National Food Safety Standards Limits of Contaminants in Food (GB 2762-2022) was then applied to understand soil limited available Cd concentration based on dose-response curves. We also derived environmental risk threshold (HC5) values for Cd remediation in agricultural soils by constructing species sensitivity distribution (SSD) curves. The results showed that Mehlich-Ⅲ best predicted Cd accumulation in crops (with 76.5% of explanation of grain Cd) and was selected as the GEM of soil available Cd for subsequent analyses. The regression coefficient (R2) of dose-response curves fitting between Cd absorption in crop tissues and soil available Cd extracted by GEM based on 30 different crop species varied from 51.0% to 79.5%, and the derived limit concentration of soil available Cd based on standard GB 2762-2022 was 0.18-0.76 mg‧kg-1. An HC5 of 0.19 mg‧kg-1 was then calculated, meaning that a concentration of available Cd in agricultural soil below 0.19 mg‧kg-1 ensures that 95% of agricultural products meet the quality and safety requirements of standard GB 2762-2022. The prediction model was well verified in the field test, indicating that can correctly estimate the soil available Cd based on the content of Cd in plant. This study provides a robust scientific framework for deriving the risk threshold for Cd remediation in agricultural soils and could be quite useful for establishing soil remediation standards.

Cellular Cd2+ fluxes in roots confirm increased Cd availability to rice (Oryza sativa L.) induced by soil acidifications.

Soil acidifications become one of the main causes restricting the sustainable development of agriculture and causing issues of agricultural product safety. In order to explore the effect of different acidification on soil cadmium (Cd) availability, soil pot culture and hydroponic (soil potting solution extraction) were applied, and non-invasive micro-test technique (NMT) was combined. Here three different soil acidification processes were simulated, including direct acidification by adding sulfuric acid (AP1), acid rain acidification (AP2) by adding artificial simulated acid rain and excessive fertilization acidification by adding (NH4)2SO4 (AP3). The results showed that for direct acidification (AP1), DTPA-Cd concentration in field soils in Liaoning (S1) and Zhejiang (S2) increased by 0.167 - 0.217 mg/kg and 0.181 - 0.346 mg/kg, respectively, compared with control group. When soil pH decreased by 0.45 units in S1, the Cd content of rice stems, leaves and roots increased by 0.48 to 6.04 mg/kg and 2.58 to 12.84 mg/kg, respectively, When the pH value of soil S1 and S2 decreased by 0.20 units, the average velocity of Cd2+ at 200 µm increased by 10.03 - 33.11 pmol/cm2/sec and 21.33 -52.86 pmol/cm2/sec, respectively, and followed the order of AP3 > AP2 > AP1. In summary, different acidification measures would improve the effectiveness of Cd, under the same pH reduction condition, fertilization acidification increased Cd availability most significantly.

Co-mutation modules capture the evolution and transmission patterns of SARS-CoV-2.

The rapid spread and huge impact of the COVID-19 pandemic caused by the emerging SARS-CoV-2 have driven large efforts for sequencing and analyzing the viral genomes. Mutation analyses have revealed that the virus keeps mutating and shows a certain degree of genetic diversity, which could result in the alteration of its infectivity and pathogenicity. Therefore, appropriate delineation of SARS-CoV-2 genetic variants enables us to understand its evolution and transmission patterns. By focusing on the nucleotides that co-substituted, we first identified 42 co-mutation modules that consist of at least two co-substituted nucleotides during the SARS-CoV-2 evolution. Then based on these co-mutation modules, we classified the SARS-CoV-2 population into 43 groups and further identified the phylogenetic relationships among groups based on the number of inconsistent co-mutation modules, which were validated with phylogenetic trees. Intuitively, we tracked tempo-spatial patterns of the 43 groups, of which 11 groups were geographic-specific. Different epidemic periods showed specific co-circulating groups, where the dominant groups existed and had multiple sub-groups of parallel evolution. Our work enables us to capture the evolution and transmission patterns of SARS-CoV-2, which can contribute to guiding the prevention and control of the COVID-19 pandemic. An interactive website for grouping SARS-CoV-2 genomes and visualizing the spatio-temporal distribution of groups is available at https://www.jianglab.tech/cmm-grouping/.

Salt stress-induced changes in soil metabolites promote cadmium transport into wheat tissues.

Soil salinity is known to improve cadmium (Cd) mobility, especially in arid soils. However, the mechanisms involved in how salt stress-associated metabolic profiles participate in mediating Cd transport in the soil-plant system remain poorly understood. This study was designed to investigate the effects of salinity-induced changes in soil metabolites on Cd bioavailability. Sodium salts in different combinations according to molar ratio (NaCl:Na2SO4=1:1; NaCl:Na2SO4:NaHCO3=1:2:1; NaCl:Na2SO4:NaHCO3:Na2CO3=1:9:9:1; NaCl:Na2SO4:NaHCO3:Na2CO3=1:1:1:1) were applied to the Cd-contaminated soils, which increased soil Cd availability by 22.36% and the Cd content in wheat grains by 36.61%, compared to the control. Salt stress resulted in soil metabolic reprogramming, which might explain the decreased growth of wheat plants and increased Cd transport from the soil into wheat tissues. For example, down-regulation of starch and sucrose metabolism reduced the production of sugars, which adversely affected growth; up-regulation of fatty acid metabolism allowed wheat plants to maintain a normal intracellular environment under saline conditions; up-regulation of the tricarboxylic acid (TCA) cycle was triggered, causing an increase in organic acid synthesis and the accumulation of organic acids, which facilitated the migration of soil Cd into wheat tissues. In summary, salt stress can facilitate Cd transport into wheat tissues by the direct effect of salt-based ions and the combined effect of altered soil physicochemical properties and soil metabolic profiles in Cd-contaminated soils.

Linking Bacterial Growth Responses to Soil Salinity with Cd Availability.

This study investigated the effects of different types of saline stress on the availability of cadmium (Cd) and bacterial growth. Changes in soil physicochemical properties and DTPA-Cd content as well as microbial responses after the addition of salts were measured. The addition of 18 g kg-1 of salts with NaCl and Na2SO4 increased the available Cd content by up to 17.80%-29.79%. Respiration rate, biomass, and relative bacterial growth decreased with increasing salt concentrations. Estimated salinity tolerance of bacterial communities based on pollution-induced community tolerance. The salinity tolerance index EC50 of the bacterial community was estimated by logistic equation and ranged from 4.32-12.63 g kg-1. Structural equation modeling showed that soil salinity stress significantly affected Cd availability and bacterial community, while bacterial growth characteristics also contributed to reducing available Cd. We conclude that saline stress can alter soil Cd availability in soils by affecting the growth characteristics of soil bacterial communities.

Effect of soil leaching on the toxicity thresholds (ECx) of Zn in soils with different properties.

Currently, the scientific basis for establishing soil environmental criteria is lacking. In order to establish reasonable soil environmental criteria values suitable for soils with different properties, this study selected soils from 16 different sites to determine the toxicity threshold of Zn based on toxicity tests of barley root elongation. In addition, leaching treatments were set up in seven soils with different properties to eliminate the influence of the accompanying anions (Cl-) on the determination of the Zn toxicity threshold. The results indicated that the toxicity thresholds of different soils vary greatly. The EC10 and EC50 ranges of barley root elongation in 16 kinds of non-leached soils were 18.5 mgkg-1 to 1618.7 mgkg-1 and 277.9 mgkg-1 to 3179.8 mgkg-1, respectively. The hormesis effect appeared in the dose response of Zn, and relative barley root elongation reached more than 150%. Leaching significantly reduced the Zn toxicity in acidic soils. The variation ranges of the leaching factor (LF) in the seven soils were LF10 = 1.1-9.3, LF50 = 1.0-3.2. The LF prediction model indicated that pH explained 81.4% of the LF variation (p < 0.01). The soil pH, cation exchange capacity (CEC), and conductivity (EC) explained 97.8% of the EC50 variation in the leached soil (p < 0.01). The results provide reference values for Zn environmental criteria.

Integrative analyses of genes associated with oxidative stress and cellular senescence in triple-negative breast cancer.

Background: Oxidative stress and cellular senescence (OSCS) have great impacts on the occurrence and progression of triple-negative breast cancer (TNBC). This study was intended to construct a prognostic model based on oxidative stress and cellular senescence related difference expression genes (OSCSRDEGs) for TNBC. Methods: The Cancer Genome Atlas (TCGA) databases and two Gene Expression Omnibus (GEO) databases were used to identify OSCSRDEGs. The relationship between OSCSRDEGs and immune infiltration was examined using single-sample gene-set enrichment analysis (ssGSEA), ESTIMATE, and the CIBERSORT algorithm. Least absolute shrinkage and selection operator (LASSO) regression analyses, Cox regression and Kaplan-Meier analysis were employed to construct a prognostic model. Receiver operating characteristic (ROC) curves, nomograms, and decision curve analysis (DCA) were used to evaluate the prognostic efficacy. Gene Set Enrichment Analysis (GSEA) Gene Ontology (GO), and Kyoto Encyclopedia of Genes and Genomes (KEGG) were utilized to explore the potential functions and mechanism. Results: A comprehensive analysis identified a total of 27 OSCSRDEGs, out of which 15 genes selected for development of a prognostic model. A high degree of statistical significance was observed for the riskscores derived from this model to accurately predict TNBC Overall survival. The decision curve analysis (DCA) and ROC curve analysis further confirmed the superior accuracy of the OSCSRDEGs prognostic model in predicting efficacy. Notably, the nomogram analysis highlighted that DMD exhibited the highest utility within the model. In comparison between high and low OSCScore groups, the infiltration abundance of immune cells was statistically different in the TCGA-TNBC dataset. Conclusion: These studies have effectively identified four essential OSCSRDEGs (CFI, DMD, NDRG2, and NRP1) and meticulously developed an OSCS-associated prognostic model for individuals diagnosed with TNBC. These discoveries have the potential to significantly contribute to the comprehension of the involvement of OSCS in TNBC.

Ecological risk threshold for Pb in Chinese soils.

Derivation of ecological risk threshold (the threshold concentration value that protect a certain proportion of species within the acceptable hazard level) of lead (Pb) is a yardstick and plays a key role in formulating soil protection policies, while the research about deducing soil Pb ecological risk threshold is still limited. In this study, toxicological data of Pb based on 30 different test endpoints was collected from our experiment and literature, and applied into interspecific extrapolation by species sensitivity distribution (SSD) method to derive the hazard concentration for 5% of species (HC5, that can protect 95% of species), the prediction models according to different soil properties were established. The results showed that EC10 (the effective concentrations of Pb that inhibit 10% of endpoint bioactivity) ranged from 205.6 to 1596.3 mg kg1, and hormesis induced by Pb were up to 118%. Toxicity data were corrected by leaching and aging process before SSD curves fitting. HC5 was then derived and prediction model was developed, as LogHC5 = 0.134 pH + 0.315 LogOC + 0.324 LogCEC + 1.077. The prediction model was well verified in the field test, indicating that can correctly estimate Pb ecotoxicity thresholds in different soils. This study provides a scientific frame for deriving the ecological risk threshold of Pb and is of great significance for ecological species protection.

Low pe+pH inhibits Cd transfer from paddy soil to rice tissues driven by S addition.

Both soil irrigation and sulfur (S) are associated with the precipitation of cadmium (Cd)-sulfide in paddy soil, their interaction affecting on Cd solubility and extractability is still unknown. This study primarily discusses the effect of exogenous S addition on the bioavailability of Cd in paddy soil under unsteady pe + pH conditions. The experiment was treated with three different water strategies: continuous dryness (CD), continuous flooding (CF), and alternating dry-wet cycles for one cycle (DW). These strategies were combined with three different S concentrations. The results indicate that the CF treatment, particularly when combined with S addition, had the most significant effect on reducing pe + pH and Cd bioavailability in the soil. The reduction of pe + pH from 10.2 to 5.5 resulted in a decrease in soil Cd availability by 58.3%, and Cd accumulation in rice grain by 52.8%, compared to the other treatments. While it was more conducive to the formation of iron plaque on the root surface in DW treatment with S addition at rice maturing stage and enhanced the gathering of Fe/S/Cd. Structural equation model (SEM) analysis further confirmed a significant negative correlation (r = -0.916) between the abundance of soil Fer-reducing bacteria (FeRB) and sulfate-reducing bacteria (SRB) like Desulfuromonas, Pseudomonas, Geobacter, and the Cd content in rice grains. This study provides a basic mechanistic understanding of how soil redox status (pe + pH), S addition, and FeRB/SRB interacted with Cd transfer in paddy soil-rice tissues.

Formation of ferrihydrite induced by low pe+pH in paddy soil reduces Cd uptake by rice: Evidence from Cd isotope fractionation.

Ferrihydrite (Fh) is an important iron mineral in paddy soil and is prone to phase transition during dynamic redox condition, which affects Cd distribution and induces Cd isotope fractionation across soil to rice. Here, we conducted rice culture experiments with or not Fh application under different irrigation regimes to study the relationship between Fe species and Cd availability, as well as the isotope ratio of Cd in different Cd pools in paddy soil-rice system. Fh addition under continuous flooding (FL) with the decrease of pe + pH from 9.36 to 3.44 promoted the formation of amorphous Fe oxides as increased by 120.1% and facilitated Cd immobilization along with the increase of Fe/Mn oxides bound Cd by 25.3%, compared with continuous drying (DY) treatment. The isotopically heavy Cd were preferentially enriched from soil to extractable Cd (Δ114/110Cdextractable Cd-soil = 0.39-0.62‰) and from soil to grain (Δ114/110Cdgrain-soil = 0.40-0.66‰) particularly at low pe + pH and with Fh addition, while light Cd were enriched in Fe/Mn oxides (Δ114/110CdFe/Mn oxides bound Cd-extractable Cd = -0.65 âˆ¼ -0.14‰). Besides, the expression of transporters involved in Cd transport in rice like OsNRAMP1, OsNRAMP1, OsHMA3, OsHMA2 and OsLCT1 were suppressed under low pe + pH condition. These findings indicated that low pe + pH facilitated Cd stabilization by the existence of more amorphous iron oxides, which induced the enrichment of heavy Cd isotope in liquid phase and light in Fe/Mn (oxy)hydroxides, respectively.

Mapping Genetic Events of SARS-CoV-2 Variants.

Genetic mutation and recombination are driving the evolution of SARS-CoV-2, leaving many genetic imprints which could be utilized to track the evolutionary pathway of SARS-CoV-2 and explore the relationships among variants. Here, we constructed a complete genetic map, showing the explicit evolutionary relationship among all SARS-CoV-2 variants including 58 groups and 46 recombination types identified from 3,392,553 sequences, which enables us to keep well informed of the evolution of SARS-CoV-2 and quickly determine the parents of novel variants. We found that the 5' and 3' of the spike and nucleoprotein genes have high frequencies to form the recombination junctions and that the RBD region in S gene is always exchanged as a whole. Although these recombinants did not show advantages in community transmission, it is necessary to keep a wary eye on the novel genetic events, in particular, the mutants with mutations on spike and recombinants with exchanged moieties on spike gene.

Ecological risk thresholds for Zn in Chinese soils.

The environmental risk threshold of a pollutant is a yardstick to measure soil environmental quality. The derivation of ecological risk thresholds of the heavy metal zinc (Zn) in soil environments based on up-to-date ecological risk assessments plays an important role in soil protection policy. According to regional soil classification, different representative soils with various degrees of acidity and alkalinity were selected, and a data set comprising ecotoxicities of Zn to 21 different test endpoints (plants, soil fauna, microorganisms, etc.) found in representative farmland soils of China was compiled based on new and published data to determine toxicological limits of Zn effects on endpoints. These limits were derived from fitted dose-response model parameters and indicated by EC10 values (the effective concentrations of Zn that inhibit 10% of endpoint bioactivity and also represents the toxicity threshold of Zn in this study) ranging from 36 mg·kg-1 to 682 mg·kg-1. The hormesis effect appeared in the dose-response curve of Zn, for example, the relative Chinese cabbage growth reached more than 120% at most. Zn concentrations added in toxicity tests were also corrected for aging and leaching effects in order to more accurately reflect field conditions. The hazardous concentrations for 5% of the species affected (HC5) were derived by the species sensitivity distribution (SSD) approach for four major types of Chinese soils: acidic (38 mg·kg-1), neutral (106 mg·kg-1), alkaline (217 mg·kg-1), and alkaline calcareous soils (155 mg·kg-1). Prediction models of ecological risk thresholds for Zn based on soil properties were generated, such as logHC5 = 0.564 + 0.218pH + 0.097OC (R2 = 0.790,p < 0.001). The predicted models based on lab test data were verified in the field, and the measured field data fell within two-fold of the prediction intervals. This work provides a scientific framework for developing soil-specific guidance on Zn toxicity thresholds.

Origin and Reversion of Omicron Core Mutations in the Evolution of SARS-CoV-2 Genomes.

Genetic analyses showed nearly 30 amino acid mutations occurred in the spike protein of the Omicron variant of SARS-CoV-2. However, how these mutations occurred and changed during the generation and development of Omicron remains unclear. In this study, 6.7 million (all publicly available data from 2020/04/01 to 2022/04/01) SARS-CoV-2 genomes were analyzed to track the origin and evolution of Omicron variants and to reveal the genetic pathways of the generation of core mutations in Omicron. The haplotype network visualized the pre-Omicron, intact-Omicron, and post-Omicron variants and revealed their evolutionary direction. The correlation analysis showed the correlation feature of the core mutations in Omicron. Moreover, we found some core mutations, such as 142D, 417N, 440K, and 764K, reversed to ancestral residues (142G, 417K, 440N, and 764N) in the post-Omicron variant, suggesting the reverse mutations provided sources for the emergence of new variants. In summary, our analysis probed the origin and further evolution of Omicron sub-variants, which may add to our understanding of new variants and facilitate the control of the pandemic.

Increased expression of SYCP2 predicts poor prognosis in patients suffering from breast carcinoma.

Overexpression of synaptonemal complex protein-2 (SYCP2) has been identified in various human papillomavirus (HPV)-related carcinomas, whereas its significant role in breast carcinoma remains unclear. The aim of this study was to elucidate the prognostic value and potential function of SYCP2 in breast carcinoma. Herein, data for breast carcinoma patients from the Gene Expression Omnibus (GEO) and The Cancer Genome Atlas database (TCGA) were analyzed. The enrichment analysis of SYCP2 including Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), Friends, and GSEA was performed. Kaplan-Meier analysis, Cox regression, and receiver operating characteristic (ROC) curves were employed for determining the predictive value of SYCP2 on clinical outcomes in patients suffering from breast carcinoma. A nomogram was generated to predict the effect arising from SYCP2 on prognosis. The association analysis of SYCP2 gene expression and diverse immune infiltration levels was conducted through ssGSEA and ESTIMATE analysis, which consisted of dendritic cell (DC), neutrophil, eosinophil, macrophage, mast cell, NK cell, and other 18 cell subtypes. The results showed that SYCP2 expression was significantly elevated in breast carcinoma tissues as compared with that of normal tissues (p < 0.001). SYCP2 plays a certain role in pathways related to DNA methylation, keratinocyte differentiation, steroid hormone biosynthesis, and immune infiltration. The high expression of SYCP2 had a significant relationship to age, pathological type, ER expression, and PR expression (p < 0.001). Kaplan-Meier survival analysis showed that patients suffering from breast carcinoma characterized by high-SYCP2 expression had a poorer prognosis than patients with low-SYCP2 expression (p = 0.005). Univariate and multivariate Cox regression analyses revealed that SYCP2 had an independent relationship to overall survival (p = 0.049). Moreover, ROC curves suggested the significant diagnostic ability of SYCP2 for breast carcinoma, and as time went on, SYCP2 had more accurate prognostic efficacy. Furthermore, a high level of SYCP2 expression was found to have a relationship to poor prognosis of breast carcinoma in the subgroups of T3, N0, and M0, and infiltrating ductal carcinoma (HR > 1, p < 0.05). The calibration plot of the nomogram indicated that the SYCP2 model has an effective predictive performance for breast carcinoma patients. Conclusively, SYCP2 plays a vital role in the pathogenesis and progression of human breast carcinoma, so it may serve as a promising prognostic molecular marker of poor survival.

A new insight into Cd reduction by flooding in paddy soil: The different dominant roles of Fe and S on Cd immobilization under fluctuant pe + pH conditions.

The unsteady comprehensive system of pe + pH strongly affects the fate of Cd in paddy soils. However, the specific pe + pH threshold determining Cd bioavailability is largely unknown especially considering the roles of Fe and S reduction. The experiment set different water managements to obtain paddy soil samples with unstable pe + pH, and chemical analysis, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) characterization were applied to reveal the dynamic process and mechanism about how Fe and S controlled Cd mobilization. The results showed that low pe + pH was favorable to soil Cd immobilization. Compared with high and medium pe + pH, the exchangeable Cd content decreased by 67.57 % and 64.71 % at low pe + pH, respectively. The XPS results showed that the contents of Fe(II) and S(-II) increased to 65.1 % and 75.2 % at low pe + pH condition, which was higher than that in other treatments. In the process of flooding for reducing Cd mobility, first it was attributed to the formation of amorphous iron oxides that can provide amount of adsorption sites for Cd. After then, S2- began to play a dominant role to combine with Cd2+ to form CdS with continuous decreased pe + pH. Therefore, Fe and S played the different dominant roles on Cd immobilization in paddy soil, and soil pe + pH value could work as a threshold.

Aging factor and its prediction models of chromium ecotoxicity in soils with various properties.

Aging of pollutants determines bioavailability and toxicity thresholds of environmental pollutants in soil. However, the ecotoxicity of chromium (Cr) rarely considers the effect of aging as well as soil properties. In order to explore the aging characteristics and establish their quantitative relationship with different soil properties, this study selected 7 soils with different properties through exogenous addition of Cr and determined its toxicity on barley root elongation. From 14d to 540d, EC10 and EC50 of barley root elongation ranged from 21.40 to 312.52 (mg·kg-1) and 50.15 to 883.88 (mg·kg-1) respectively. The hormesis appeared in the dose-response curve of acid soil as relative barley root elongation reached >110 % compared with the control. Extended aging time of Cr from 14d to 540d was associated with the attenuation of the toxicity of Cr, as the aging factor increased from 1.26 to 6.09 for EC50, from 0.88 to 4.98 for EC10. The prediction model of AFEC50 and soil properties is lg (AF360d) = 0.306lg Clay+0.026lg CEC + 0.240 (R2 = 0.872, P < 0.01). The results demonstrated that with the extension of aging time, the toxicity of Cr decreased at 360d and reached a slow reaction stage, after that soil OC, Clay and CEC could well explain the aging procedure of Cr (VI). These results are beneficial for risk assessment of Cr contaminated soils and establishment of a soil environmental quality criteria for Cr.

Ecological toxicity (ECx) of Pb and its prediction models in Chinese soils with different physiochemical properties.

The lack of toxicological data becomes the main bottleneck of ecological risk assessment of lead (Pb) in Chinese soils. The present study assessed Pb toxicity on three underground test endpoints (barley root elongation, earthworm avoidance response, and substrate-induced respiration (SIR) of microorganism) in 10 different soils. Hormetic dose-response induced by Pb was >118 % for earthworm avoidance response. EC10 and EC50 (the effective concentrations of Pb that inhibit 10 % or 50 % of endpoint bioactivity and also represents the toxicity threshold of Pb) after leaching increased by 0.32-8.73 times, and 1.02-3.75 times, respectively. Leaching factor (LF) prediction models indicated pH and cation exchange capacity (CEC) were the vital predictors for LF10 and LF50, explaining 60.6 % and 73.1 % of variations, respectively. SIR was one sensitive test endpoint for Pb toxicity, with the lowest of EC10 and EC50 values (from 373.7 to 1008.5 mg·kg-1, and from 837.1 to 2869.0 mg·kg-1, respectively). The best prediction models between ECx and soil properties is LogEC50 = 1.324Log(pH) + 0.423Log(CEC) + 1.742 (R2 = 0.761, p < 0.01). The results displayed significant implications for deriving ECx of Pb, and provided a scientific basis for soil ecological risk assessment of Pb.

Progress and Challenge in Computational Identification of Influenza Virus Reassortment.

Genomic reassortment is an important evolutionary mechanism for influenza viruses. In this process, the novel viruses acquire new characteristics by the exchange of the intact gene segments among multiple influenza virus genomes, which may cause flu endemics and epidemics within or even across hosts. Due to the safety and ethical limitations of the experimental studies on influenza virus reassortment, numerous computational researches on the influenza virus reassortment have been done with the explosion of the influenza virus genomic data. A great amount of computational methods and bioinformatics databases were developed to facilitate the identification of influenza virus reassortments. In this review, we summarized the progress and challenge of the bioinformatics research on influenza virus reassortment, which can guide the researchers to investigate the influenza virus reassortment events reasonably and provide valuable insight to develop the related computational identification tools.

Fe(III) reduction due to low pe+pH contributes to reducing Cd transfer within a soil-rice system.

Effect of Fe redox state caused by low soil pe+pH levels on Cd uptake by rice is unclear. Rice grown in pots of Cd-contaminated paddy soil were subjected to different irrigation regimes: flooding, intermittent flooding (Int-FL), and sustained soil moisture at 70% water holding capacity (WHC). Results showed low pe+pH (5.52 and 7.09) in flooding treatment significantly increased relative abundances of Fe-reducing bacteria (FeRB) (6.29% and 4.51%), especially members within the Clostridium, Geobacter and Desulfuromonadia genera. Stimulation of FeRB activity induced Fe(III) reduction and increased Fe2+ content in flooded soils, which promoted Cd sequestration in low-crystalline fraction of IP (IP-Feh-Cd) and Cd bonded to amorphous Fe-oxides (amFeox-Cd). The 24.9-62.4% higher amFeox-Cd content was the important factor for 20.4-44.2% lower CaCl2-extractable Cd content in flooding treatment than those in other treatments. Soil submergence reduced Cd uptake by rice at tillering and booting stages, the critical periods of Cd transport in the soil-rice system, which was attributed to the increases in dissolved Fe2+ and IP-Feh-Cd contents and decrease in CaCl2-Cd content. Therefore, maintaining flooding during the tillering and booting stages may be an effective strategy to reduce Cd uptake by rice cultivated in Cd-contaminated soil.