Anaerobic ammonium oxidation (anammox) is a promising biological nitrogen removal process, due to its advantages of high efficiency and low cost. However, problems remain in the application, such as ...long startup period and susceptibility to environmental variations. Quorum sensing (QS), as a means of bacterial communication, attracts more attentions in regulating aggregation behavior and microbial density. Many physiological characteristics of anammox bacteria have been confirmed to be associated with QS, including specific anammox activity, growth rate and the production of extracellular polymeric substances (EPS), which directly affect the performance of anammox process. Therefore, a comprehensive understanding of the QS in anammox process is prerequisite. This work systematically reviewed the role and application of QS in the anammox process with the focus on mechanism. Additionally, current challenges and research needs were proposed.
Summary
Plant protoplasts are useful for assessing the efficiency of clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR‐associated protein 9 (Cas9) mutagenesis. We improved the ...process of protoplast isolation and transfection of several plant species. We also developed a method to isolate and regenerate single mutagenized Nicotianna tabacum protoplasts into mature plants. Following transfection of protoplasts with constructs encoding Cas9 and sgRNAs, target gene DNA could be amplified for further analysis to determine mutagenesis efficiency. We investigated N. tabacum protoplasts and derived regenerated plants for targeted mutagenesis of the phytoene desaturase (NtPDS) gene. Genotyping of albino regenerants indicated that all four NtPDS alleles were mutated in amphidiploid tobacco, and no Cas9 DNA could be detected in most regenerated plants.
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•Sulfide (20 mg L−1) could reduce the specific anammox activity by 61.7%.•Protein-like substances were quenched due to sulfide stress.•Sulfide addition led Candidatus Kuenenia ...decrease while Thiobacillus increase.•Functional gene abundances significantly decreased with 20 mg L−1 sulfide.
Sulfide has attracted increasing attention due to its odor nuisance, toxicity and corrosion. Although variations in the nitrogen removal performance of anammox under sulfide stress have been reported previously, understanding the microorganisms at the molecular level is of greater significance. This study first deciphered the microbial community and functional gene response of anammox sludge to sulfide stress. Results showed that 20 mg L−1 sulfide could reduce specific anammox activity by 61.7%. The protein-like substances within extracellular polymeric substances were quenched at the end of the experiment. Moreover, the relative abundance of Candidatus Kuenenia significantly decreased from 28.7% to 6.4% while Thiobacillus increased from 0 to 7.2% due to sulfide stress. Furthermore, the abundances of functional genes (hzsA, hdh, nirK and nirS) significantly decreased when the sulfide concentration reached 20 mg L−1. These findings provide a further theoretical basis for the anammox process for nitrogen removal from wastewater containing sulfide.
The wide existence of saline wastewater has attracted public attention due to its environmental destructiveness. The potential of anammox to treat saline wastewater was systematically evaluated in ...this study. Three bioreactors with different salinity increasing strategies (R1: inhibition kinetic; R2: gradient increasing; R3: pulsed increasing) were operated to identify the optimal acclimation mode. The results showed that the inhibition of anammox activity by salinity was mainly caused by the loss of enzyme activity. Under the condition of 25.0 g NaCl L−1, the highest nitrogen removal rate of R3 (2.36 ± 0.14 kg N m−3 d−1) indicated that the pulsed strategy might be optimal. Changes in microbial community might be the primary reason lead to different acclimatization results. The relative abundance of anammox bacteria increased by 37.19% in R1 and by 46.81% in R3, but remained stable in R2 with increasing salinity. Dynamic varations in bacterial interactions, proteins, and functional genes revealed the potential resistance mechanisms of bacteria to salinity. The present work provides a novel approach and guidance for the treatment of nitrogen-rich saline wastewater by the anammox process.
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•Three acclimation strategies for salt-tolerant anammox process were proposed for the first time.•The inhibition of FAB by salinity was mainly caused by the loss of enzyme activity.•High abundance of anammox bacteria led to the excellent acclimatization results.•Corresponding strategies can be selected based on the wastewater characteristics.
The recent release of genomic sequences for 3000 rice varieties provides access to the genetic diversity at species level for this crop. We take advantage of this resource to unravel some features of ...the retrotranspositional landscape of rice. We develop software TRACKPOSON specifically for the detection of transposable elements insertion polymorphisms (TIPs) from large datasets. We apply this tool to 32 families of retrotransposons and identify more than 50,000 TIPs in the 3000 rice genomes. Most polymorphisms are found at very low frequency, suggesting that they may have occurred recently in agro. A genome-wide association study shows that these activations in rice may be triggered by external stimuli, rather than by the alteration of genetic factors involved in transposable element silencing pathways. Finally, the TIPs dataset is used to trace the origin of rice domestication. Our results suggest that rice originated from three distinct domestication events.
This study adopts the Bayesian neural network (BNN) integrated with a strong non-linear fitting capability and uncertainty, which has not previously been used in geotechnical engineering, to propose ...a modelling strategy in developing prediction models for soil properties. The compression index C
c
and undrained shear strength s
u
of clays are selected as examples. Variational inference (VI) and Monte Carlo dropout (MCD), two theoretical frameworks for solving and approximating BNN, respectively, are employed and compared. The results indicate that the BNN focused on identifying patterns in datasets, and the predicted C
c
and s
u
show excellent agreement with the actual values. The reliability of the predicted results using BNN is high in the area of dense datasets. In contrast, the BNN demonstrates low reliability in the predicted result in the area of sparse datasets. Additionally, a novel parametric analysis method in combination with the cumulative distribution function is proposed. The analysis results indicate that the BNN-based models are capable of capturing the relationships of input parameters to the C
c
and s
u
. BNN, with its strong prediction capability and reliable evaluation, therefore, shows great potential to be applied in geotechnical design.
Summary
A comparative study of optimization techniques for identifying soil parameters in geotechnical engineering was first presented. The identification methodology with its 3 main parts, error ...function, search strategy, and identification procedure, was introduced and summarized. Then, current optimization methods were reviewed and classified into 3 categories with an introduction to their basic principles and applications in geotechnical engineering. A comparative study on the identification of model parameters from a synthetic pressuremeter and an excavation tests was then performed by using 5 among the mostly common optimization methods, including genetic algorithms, particle swarm optimization, simulated annealing, the differential evolution algorithm and the artificial bee colony algorithm. The results demonstrated that the differential evolution had the strongest search ability but the slowest convergence speed. All the selected methods could reach approximate solutions with very small objective errors, but these solutions were different from the preset parameters. To improve the identification performance, an enhanced algorithm was developed by implementing the Nelder‐Mead simplex method in a differential algorithm to accelerate the convergence speed with strong reliable search ability. The performance of the enhanced optimization algorithm was finally highlighted by identifying the Mohr‐Coulomb parameters from the 2 same synthetic cases and from 2 real pressuremeter tests in sand, and ANICREEP parameters from 2 real pressuremeter tests in soft clay.
A motor imagery EEG (MI-EEG) signal is often selected as the driving signal in an active brain computer interface (BCI) system, and it has been a popular field to recognize MI-EEG images via ...convolutional neural network (CNN), which poses a potential problem for maintaining the integrity of the time-frequency-space information in MI-EEG images and exploring the feature fusion mechanism in the CNN. However, information is excessively compressed in the present MI-EEG image, and the sequential CNN is unfavorable for the comprehensive utilization of local features. In this paper, a multidimensional MI-EEG imaging method is proposed, which is based on time-frequency analysis and the Clough-Tocher (CT) interpolation algorithm. The time-frequency matrix of each electrode is generated via continuous wavelet transform (WT), and the relevant section of frequency is extracted and divided into nine submatrices, the longitudinal sums and lengths of which are calculated along the directions of frequency and time successively to produce a 3 × 3 feature matrix for each electrode. Then, feature matrix of each electrode is interpolated to coincide with their corresponding coordinates, thereby yielding a WT-based multidimensional image, called WTMI. Meanwhile, a multilevel and multiscale feature fusion convolutional neural network (MLMSFFCNN) is designed for WTMI, which has dense information, low signal-to-noise ratio, and strong spatial distribution. Extensive experiments are conducted on the BCI Competition IV 2a and 2b datasets, and accuracies of 92.95% and 97.03% are yielded based on 10-fold cross-validation, respectively, which exceed those of the state-of-the-art imaging methods. The kappa values and p values demonstrate that our method has lower class skew and error costs. The experimental results demonstrate that WTMI can fully represent the time-frequency-space features of MI-EEG and that MLMSFFCNN is beneficial for improving the collection of multiscale features and the fusion recognition of general and abstract features for WTMI.
Graphical abstract
To achieve the efficient treatment of high-strength ammonium wastewaters, a two-stage anammox process was proposed in this study. The nitrogen loading rates (NLR) of two anammox reactors were ...increased to 60.19 g N L−1 d−1 (R1) and 24.32 g N L−1 d−1 (R2), through reducing hydraulic retention time (HRT) and increasing ammonium concentration. Afterwards, the reactors were operated in series at variable temperatures (6.15–34.13 °C) for 240 days to treat the synthetic high-ammonium containing wastewater, with the effluent of R1 pumping into R2 as influent. Finally, the advanced treatment of the high-strength ammonium wastewater (490 mg NH4+-N L−1 and 980 mg TN L−1) was successfully achieved, and nitrogen removal efficiency (NRE) maintained at 83.25 ± 9.48%. During the whole operational period (400 days), the richness and diversity of microbial community in two reactors generally increased, and Candidatus Kuenenia was identified as the dominant anammox bacterium. In serial-operation phase, the dominant phylum changed from Planctomycetes to Proteobacteria, and the average relative abundance of Proteobacteria 39.61% in R1 and 48.32% in R2. Variations in bacterial abundances and distributions were closely related to the substrate concentration and temperature. Correspondingly, the expression levels of most functional genes were reduced by low temperature, and were slightly different in settling, middle and floating sludge. Nitrogen transformation pathway in each phase was also determined based on the gene expression levels, and main pathways in both reactors included anammox and first step of denitrification (NO3−→NO2−). All findings of this study provide new insights into the potential application of the two-stage anammox process to treat high-strength ammonium wastewater under variable temperature conditions.
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•A novel anammox process was proposed to treat high-strength ammonium wastewater.•The two-stage anammox process could maintain efficient and stable for a long term.•Microbial community composition and distribution changed.•Expression levels of functional genes were slightly affected by low temperature.•Main nitrogen transformation pathways included anammox and NO3−.→NO2−.
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