The performance of homopolymer detection using dichromatic and tetrachromatic fluorogenic next-generation sequencing platforms.

OBJECTIVES: Homopolymer (HP) sequencing is error-prone in next-generation sequencing (NGS) assays, and may induce false insertion/deletions and substitutions. This study aimed to evaluate the performance of dichromatic and tetrachromatic fluorogenic NGS platforms when sequencing homopolymeric regions. RESULTS: A HP-containing plasmid was constructed and diluted to serial frequencies (3%, 10%, 30%, 60%) to determine the performance of an MGISEQ-2000, MGISEQ-200, and NextSeq 2000 in HP sequencing. An evident negative correlation was observed between the detected frequencies of four nucleotide HPs and the HP length. Significantly decreased rates (P < 0.01) were found in all 8-mer HPs in all three NGS systems at all four expected frequencies, except in the NextSeq 2000 at 3%. With the application of a unique molecular identifier (UMI) pipeline, there were no differences between the detected frequencies of any HPs and the expected frequencies, except for poly-G 8-mers using the MGI 200 platform. UMIs improved the performance of all three NGS platforms in HP sequencing. CONCLUSIONS: We first constructed an HP-containing plasmid based on an EGFR gene backbone to evaluate the performance of NGS platforms when sequencing homopolymeric regions. A highly comparable performance was observed between the MGISEQ-2000 and NextSeq 2000, and introducing UMIs is a promising approach to improve the performance of NGS platforms in sequencing homopolymeric regions.

Transcriptional analysis of the dimorphic fungus Umbilicaria muehlenbergii reveals the molecular mechanism of phenotypic transition.

The lichen-forming fungus Umbilicaria muehlenbergii undergoes a phenotypic transition from a yeast-like to a pseudohyphal form. However, it remains unknown if a common mechanism is involved in the phenotypic switch of U. muehlenbergii at the transcriptional level. Further, investigation of the phenotype switch molecular mechanism in U. muehlenbergii has been hindered by incomplete genomic sequencing data. Here, the phenotypic characteristics of U. muehlenbergii were investigated after cultivation on several carbon sources, revealing that oligotrophic conditions due to nutrient stress (reduced strength PDA (potato dextrose agar) media) exacerbated the pseudohyphal growth of U. muehlenbergii. Further, the addition of sorbitol, ribitol, and mannitol exacerbated the pseudohyphal growth of U. muehlenbergii regardless of PDA medium strength. Transcriptome analysis of U. muehlenbergii grown in normal and nutrient-stress conditions revealed the presence of several biological pathways with altered expression levels during nutrient stress and related to carbohydrate, protein, DNA/RNA and lipid metabolism. Further, the results demonstrated that altered biological pathways can cooperate during pseudohyphal growth, including pathways involved in the production of protectants, acquisition of other carbon sources, or adjustment of energy metabolism. Synergistic changes in the functioning of these pathways likely help U. muehlenbergii cope with dynamic stimuli. These results provide insights into the transcriptional response of U. muehlenbergii during pseudohyphal growth under oligotrophic conditions. Specifically, the transcriptomic analysis indicated that pseudohyphal growth is an adaptive mechanism of U. muehlenbergii that facilitates its use of alternative carbon sources to maintain survival.

Understanding and Calibration of Charge Storage Mechanism in Cyclic Voltammetry Curves.

Noticeable pseudo-capacitance behavior out of charge storage mechanism (CSM) has attracted intensive studies because it can provide both high energy density and large output power. Although cyclic voltammetry is recognized as the feasible electrochemical technique to determine it quantitatively in the previous works, the results are inferior due to uncertainty in the definitions and application conditions. Herein, three successive treatments, including de-polarization, de-residual and de-background, as well as a non-linear fitting algorithm are employed for the first time to calibrate the different CSM contribution of three typical cathode materials, LiFePO4 , LiMn2 O4 and Na4 Fe3 (PO4 )2 P2 O7 , and achieve well-separated physical capacitance, pseudo-capacitance and diffusive contributions to the total capacity. This work can eliminate misunderstanding concepts and correct ambiguous results of the pseudo-capacitance contribution and recognize the essence of CSM in electrode materials.

Mg storage properties of hollow copper selenide nanocubes.

Rechargeable Mg batteries are thought to be suitable for scalable energy-storage applications because of their high safety and low cost. However, the bivalent Mg2+ cations suffer from sluggish solid-state diffusion kinetics. Herein, a hollow morphological approach is introduced to design copper selenide cathodes for rechargeable Mg batteries. Hollow Cu2-xSe nanocubes are fabricated via a solution reaction and their Mg-storage properties are investigated in comparison to simple nanoparticles. The hollow structures accommodate the volume change during magnesiation/demagnesiation and maintain material integrity, and thus a remarkable cycling stability of over 200 cycles is achieved. A kinetic study demonstrates that a hollow structure favors solid-phase Mg2+ diffusion, and therefore the hollow Cu2-xSe nanocubes exhibit a high capacity of 250 mA h g-1 at 100 mA g-1 as well as a superior rate capability. Mechanism investigation indicates that Cu2-xSe experiences a structure conversion during which a phase transformation occurs. This work develops a facile method for the preparation of hollow copper selenides and highlights the advantages of hollow structures in the design of high-performance Mg-storage materials.

Correction to: Structure and function of the Arctic and Antarctic marine microbiota as revealed by metagenomics.

An amendment to this paper has been published and can be accessed via the original article.

Structure and function of the Arctic and Antarctic marine microbiota as revealed by metagenomics.

BACKGROUND: The Arctic and Antarctic are the two most geographically distant bioregions on earth. Recent sampling efforts and following metagenomics have shed light on the global ocean microbial diversity and function, yet the microbiota of polar regions has not been included in such global analyses. RESULTS: Here a metagenomic study of seawater samples (n = 60) collected from different depths at 28 locations in the Arctic and Antarctic zones was performed, together with metagenomes from the Tara Oceans. More than 7500 (19%) polar seawater-derived operational taxonomic units could not be identified in the Tara Oceans datasets, and more than 3,900,000 protein-coding gene orthologs had no hits in the Ocean Microbial Reference Gene Catalog. Analysis of 214 metagenome assembled genomes (MAGs) recovered from the polar seawater microbiomes, revealed strains that are prevalent in the polar regions while nearly undetectable in temperate seawater. Metabolic pathway reconstruction for these microbes suggested versatility for saccharide and lipids biosynthesis, nitrate and sulfate reduction, and CO2 fixation. Comparison between the Arctic and Antarctic microbiomes revealed that antibiotic resistance genes were enriched in the Arctic while functions like DNA recombination were enriched in the Antarctic. CONCLUSIONS: Our data highlight the occurrence of dominant and locally enriched microbes in the Arctic and Antarctic seawater with unique functional traits for environmental adaption, and provide a foundation for analyzing the global ocean microbiome in a more complete perspective. Video abstract.

Flexible high dielectric thin films based on cellulose nanofibrils and acid oxidized multi-walled carbon nanotubes.

Flexible high dielectric materials are of prime importance for advanced portable, foldable and wearable devices. A series of flexible high dielectric thin films based on cellulose nanofibrils (CNF) and acid oxidized multi-walled carbon nanotubes (o-MWCNT) was prepared in aqueous solution. Though no organic solvent was involved during the preparation, the SEM images showed that o-MWCNTs have good distribution within the CNF matrix. The dielectric constant of CNF/o-MWCNT (6.2 wt%) composite films was greatly increased from 25.24 for pure CNF to 73.88, while the loss tangent slightly decreased from 0.70 to 0.68, and the AC conductivity decreased from 3.15 × 10-7 S cm-1 for CNF to 1.77 × 10-7 S cm-1 (at 1 kHz). The abnormal decrease of loss tangent and AC conductivity were attributed to the introduction of oxide-containing groups on the surface of MWCNTs. The nanocomposite films showed excellent flexibility such that they could be bent a thousand times without visible damage. The presence of MWCNTs also helped to improve the thermal stability of the composite films. The excellent dielectric and mechanical properties of the CNF/o-MWCNT composite film demonstrate its great potential to be utilized in the field of energy storage.

High dielectric thin films based on barium titanate and cellulose nanofibrils.

A series of composite films based on tetragonal barium titanate (BTO) and cellulose nanofibrils (CNF) with high dielectric constant are prepared using a casting method in aqueous solution. No organic solvent is involved during the preparation, which demonstrates the environmental friendliness of the novel material. With less than 30 wt% of filler loading, the excellent distribution of BTO nanoparticles within the CNF matrix is revealed by the FE-SEM images. The dielectric constant of the CNF/BTO (30 wt%) composite film reaches up to 188.03, which is about seven times higher than that of pure CNF (25.24), while the loss tangent only rises slightly from 0.70 to 1.21 (at 1 kHz). The thin films kept their dielectric properties on an acceptable level after repeatedly twisting or rolling 10 times. The improvement of thermal stability is observed with the presence of BTO. The outstanding dielectric properties of the CNF/BTO composite film indicates its great potential to be utilized in energy storage applications.

Water masses influence bacterioplankton community structure in summer Kongsfjorden.

To ascertain the saying "Everything is everywhere, but the environment selects", it was imperative to find out the main factor influencing bacterioplankton composition at genus level of Kongsfjorden where was influenced both by glacier melting water and Atlantic water. Thus, bacterioplankton diversity was investigated using pyrosequencing. In addition, nutrients, chlorophyll a, in situ temperature and salinity were measured. There were seventeen of 33 identified genera with relative abundance > 0.1%. Redundancy analysis showed that 73.02% of bacterioplankton community variance could be explained by environmental parameters. Furthermore, most of the abundant genera demonstrated significant correlation with environment parameters revealed by correlation analysis. Moreover, phosphate, nitrate and Chl a concentration, and the abundance of top nine identified genera varied with water mass significantly as shown by analysis of variance. Our results supported the notion that environmental factors, especially water mass had significant effect on bacterioplankton distribution at genus level. Considering the high sensitivity to environmental change and low error rate in identification, bacterioplankton at genus level could be potential bio-markers for monitoring environmental changes.

CoSe2 hollow microspheres, nano-polyhedra and nanorods as pseudocapacitive Mg-storage materials with fast solid-state Mg2+ diffusion kinetics.

CoSe2 materials with different nanostructures are used as pseudocapacitive Mg-storage cathodes, which exhibit fast solid-state Mg2+ ions diffusion kinetics. In this work, CoSe2 with different nanostructures including hollow microspheres (H-CoSe2), nano-polyhedra (P-CoSe2) and nanorods (R-CoSe2) are fabricated by using facile one-step hydrothermal methods, and used as pseudocapacitive electrodes for rechargeable Mg batteries. It is observed that R-CoSe2 exhibits the highest reversible capacity of 233 mA h g-1 at 50 mA g-1 and an excellent rate capability of 116 mA h g-1 at 500 mA g-1, ascribing to the 1D nanorod structure which facilitates the solid-state Mg2+ diffusion. Benefitting from the stable hierarchical structure, H-CoSe2 exhibits a superior long-term cycling stability of 350 cycles. A mechanism study indicates that the redox reaction reversibly occurs between CoSe2 and metallic Co0. Further investigation demonstrates that the fast solid-state Mg2+ diffusion kinetics and surface-controlled pseudocapacitive behavior enhance the electrochemical performance. This work highlights a novel and efficient Mg-storage strategy of using pseudocapacitive materials, and the performance and solid-state Mg2+ diffusion kinetics of CoSe2 could be optimized by rational structural tailoring.

Facile synthesis and electrochemical Mg-storage performance of Sb2Se3 nanowires and Bi2Se3 nanosheets.

Rechargeable Mg batteries are considered as low-cost and reliable candidates for efficient energy storage, but their development is blocked by the lack of suitable cathode materials. In this work, Sb2Se3 nanowires and Bi2Se3 nanosheets are fabricated by facile one-step hydrothermal methods and their Mg-storage performances are systematically investigated. The results show that the Bi2Se3 nanosheets with stable hierarchical 2D structure exhibit a better performance. Because of its thin nanosheet structure, Bi2Se3 provides a high Mg-storage capacity of 144 mA h g-1 and a remarkable rate capability with 65 mA h g-1 delivered at 1000 mA g-1. Bi2Se3 also exhibits an outstanding cyclability over 350 cycles owing to its hierarchical structure. Furthermore, this study reveals that the electrochemical charge/discharge cycling is a typical conversion reaction occurring between Bi3+ and metallic Bi0. Kinetic investigation suggests that the high performance of Bi2Se3 is attributed to both its intrinsic nature and its thin nanosheet structure facilitating solid-state Mg2+ diffusion. The present work highlights the selection principle of conversion cathodes for rechargeable Mg batteries, namely matching a soft anion with a quasi-soft metal cation. Moreover, the facile synthesis approach is also used for low-dimensional main-group VI metal chalcogenides to improve the Mg-storage performance.

Rechargeable Mg batteries based on a Ag2S conversion cathode with fast solid-state Mg2+ diffusion kinetics.

Rechargeable Mg batteries are promising candidates for highly safe, large-scale energy storage batteries due to the low-cost and non-dendritic metallic Mg anode. However, exploring high-performance cathodes remains a great challenge blocking their development. Herein, a rechargeable Mg battery is established with a Ag2S conversion cathode, providing a highly reversible capacity of 120 mA h g-1 at 50 mA g-1, a superior rate capability of 70 mA h g-1 at 500 mA g-1, and an outstanding long-term cyclability over 400 cycles. The mechanism was investigated using XRD, TEM and XPS in addition to electrochemical measurements, and indicated a two-stage magnesiation: first, Mg2+ intercalation into Ag2S and then a conversion reaction to form metallic Ag0 and MgS. The solid-state Mg2+ diffusion coefficients are as high as 3.6 × 10-9 and 3.1 × 10-10 cm2 s-1 for the intercalation and conversion reactions, respectively, which explains the high performance of the Ag2S cathode. This work provides scientific insights for the selection of a promising conversion cathode by the combination of soft anions and soft transition metal cations.

Rechargeable Mg-M (M = Li, Na and K) dual-metal-ion batteries based on a Berlin green cathode and a metallic Mg anode.

Mg-M (M = Li, Na and K) dual-metal-ion batteries featuring a dendrite-free Mg anode and an alkali-metal-ion storage cathode are promising safe energy storage systems. However, the compatibility between cathode materials and insertion cations might largely limit the electrochemical performance of the cathodes. In this work, three types of Mg-M (M = Li, Na and K) dual-metal-ion batteries are constructed with a Berlin green (FeFe(CN)6) cathode. The FeFe(CN)6 cathode is compatible with the dual-salt Mg2+/M+ (M = Li, Na and K) electrolytes, and delivers a high reversible capacity of 120 mA h g-1 at 50 mA g-1, with no capacity fading over 50 cycles in Mg-Na batteries. The Mg-Na battery also shows an outstanding rate capability, providing 85 mA h g-1 at 1000 mA g-1 and superior long-term cyclability over 800 cycles. The electrochemical performance comparison between Mg-Li, Mg-Na and Mg-K dual-metal-ion batteries demonstrates the significance of the appropriate hydrated ionic radius and dehydrated ionic radius for the insertion of cations with the FeFe(CN)6 cathode. This work provides new design strategies for stable and high energy density cathodes, and opens a new avenue for building safe and high-performance Mg-M (M = Li, Na and K) dual-metal-ion batteries for practical applications.

a-MoS3@CNT nanowire cathode for rechargeable Mg batteries: a pseudocapacitive approach for efficient Mg-storage.

Rechargeable Mg batteries are promising candidates for highly safe large-scale energy storage batteries owing to their low-cost and non-dendritic metallic Mg anode. However, exploration of high-performance cathodes remains a great challenge hindering their development. Herein, a new pseudocapacitive Mg-storage nanowire material (a-MoS3@CNT) is constructed with a carbon nanotube (CNT) core and an amorphous MoS3 (a-MoS3) outer layer (15 nm thick). The nanowire cathode exhibits a high reversible capacity of 175 mA h g-1 at 100 mA g-1, a good rate performance of 50 mA h g-1 at 1000 mA g-1, and an outstanding long-term cyclability over 500 cycles. Further investigation of the mechanism demonstrates that the Mg-storage of a-MoS3@CNT is mainly achieved by the pseudocapacitance of a-MoS3, in which Mg2+ ions show fast solid-state diffusion kinetics. The present results demonstrate a new approach for efficient Mg-storage using pseudocapacitive materials, and the performance and solid-state Mg2+ diffusion kinetics could be optimized by delicate morphology tailoring.

Zero-strain Na4Fe7(PO4)6 as a novel cathode material for sodium-ion batteries.

We report for the first time a zero-strain cathode, Na4Fe7(PO4)6, for sodium-ion batteries (SIBs). This new iron-based polyanionic cathode delivers a reversible capacity of 66.5 mA h g-1 at 5 mA g-1 with almost 100% capacity retention over 1000 cycles under 200 mA g-1, and the outstanding performance benefits from single-phase-transition processes with a tiny volume change of only ∼0.24%.

Recent Progress in Rechargeable Sodium-Ion Batteries: toward High-Power Applications.

The increasing demands for renewable energy to substitute traditional fossil fuels and related large-scale energy storage systems (EES) drive developments in battery technology and applications today. The lithium-ion battery (LIB), the trendsetter of rechargeable batteries, has dominated the market for portable electronics and electric vehicles and is seeking a participant opportunity in the grid-scale battery market. However, there has been a growing concern regarding the cost and resource availability of lithium. The sodium-ion battery (SIB) is regarded as an ideal battery choice for grid-scale EES owing to its similar electrochemistry to the LIB and the crust abundance of Na resources. Because of the participation in frequency regulation, high pulse-power capability is essential for the implanted SIBs in EES. Herein, a comprehensive overview of the recent advances in the exploration of high-power cathode and anode materials for SIB is presented, and deep understanding of the inherent host structure, sodium storage mechanism, Na+ diffusion kinetics, together with promising strategies to promote the rate performance is provided. This work may shed light on the classification and screening of alternative high rate electrode materials and provide guidance for the design and application of high power SIBs in the future.

Coccomyxagreatwallensis sp. nov. (Trebouxiophyceae, Chlorophyta), a lichen epiphytic alga from Fildes Peninsula, Antarctica.

A single-celled green alga Coccomyxagreatwallensis Shunan Cao & Qiming Zhou, sp. nov., isolated from a specimen of Antarctic lichen Psoromahypnorum (Vahl) Gray, is described and illustrated based on a comprehensive investigation of morphology, ultrastructure, ecology and phylogeny. The cells of C.greatwallensis are ovoid to long ellipsoidal and measured 3-5 µm × 6-12 µm. The new species has distinct ITS rDNA and SSU rDNA sequences and differs from the phylogenetic closely related species C.antarctica, C.arvernensis and C.viridis in cell size, distribution and habitat.

Copper sulfide nanoparticles as high-performance cathode materials for magnesium secondary batteries.

Magnesium secondary batteries are promising candidates for large-scale energy storage systems with high safety, because of the dendrite-free electrodeposition of the magnesium anode. However, the search for available cathode materials remains a significant challenge, hindering their development. In this work, we report copper sulfide nanoparticles as high-performance cathode materials for magnesium secondary batteries, which deliver a high reversible capacity of 175 mA h g-1 at 50 mA g-1. The cathode also shows an excellent rate capability providing 90 mA h g-1 at 1000 mA g-1 and an outstanding long-term cyclability over 350 cycles. The beneficial properties are ascribed to the small-sized copper sulfide particles which facilitate the solid-state diffusion kinetics. Further investigation on the mechanism demonstrates that the reaction is a typical conversion reaction, and the excellent cycling stability is due to the CuS nanoparticles which are not facile to aggregate during cycling. This work introduces an abundant, low-cost and high-performance cathode material for magnesium secondary batteries, and provides feasibility for the practical application of magnesium secondary battery systems in large-scale energy storage devices.

Coccomyxa antarctica sp. nov. from the Antarctic lichen Usnea aurantiacoatra.

The single celled green alga Coccomyxa antarctica Shunan Cao & Qiming Zhou, sp. nov. was isolated from the Antarctic torrential lichen Usnea aurantiacoatra (Jacq.) Bory. It is described and illustrated based on a comprehensive study of its morphology, ultrastructure, ecology and phylogeny. C. antarctica is a lichenicolous alga which has elongated cells and contains a parietal chloroplast as observed under the microscope. C. antarctica is clearly different from other species by phylogenetic analysis (ITS rDNA and SSU rDNA sequences), also it differs from its phylogenetic closely species C. viridis by its larger cell size.

Exploring the roles of substrate-binding surface of the chaperone site in the chaperone activity of trigger factor.

Trigger factor (TF) is a key component of the prokaryotic chaperone network, which is involved in many basic cellular processes, such as protein folding, protein trafficking, and ribosome assembly. The major chaperone site of TF has a cradle-like structure in which protein substrate may fold without interference from other proteins. Here, we investigated in vivo and in vitro the roles of hydrophobic and charged patches on the edge and interior of cradle during TF-assisted protein folding. Our results showed that most of the surface of the cradle was involved in TF-assisted protein folding, which was larger than found in early studies. Although the inner surface of cradle was mostly hydrophobic, both hydrophobic and electrostatic patches were indispensable for TF to facilitate correct protein folding. However, hydrophobic patches were more important for the antiaggregation activity of TF. Furthermore, it was found that the patches on the surface of cradle were involved in TF-assisted protein folding in a spatial and temporal order. These results suggest that the folding-favorable interface between the cradle and substrate was dynamic during TF-assisted protein folding, which enabled TF to be involved in the folding of substrate in an aggressive manner rather than acting as a classic holdase.-Fan, D., Cao, S., Zhou, Q., Zhang, Y., Yue, L., Han, C., Yang, B., Wang, Y., Ma, Z., Zhu, L., Liu, C. Exploring the roles of substrate-binding surface of chaperone site in the chaperone activity of trigger factor.