Comamonas sp. strain CNB-1 grows on 4-chloronitrobenzene (4-CNB) and nitrobenzene as sole carbon and nitrogen sources. In this study, two genetic segments, cnbB-orf2-cnbA and cnbR-orf1-cnbCaCbDEFGHI, located on a newly isolated plasmid, pCNB1 (ca. 89 kb), and involved in 4-CNB/nitrobenzene degradation, were characterized. Seven genes (cnbA, cnbB, cnbCa, cnbCb, cnbD, cnbG, and cnbH) were cloned and functionally expressed in recombinant Escherichia coli, and they were identified as encoding 4-CNB nitroreductase (CnbA), 1-hydroxylaminobenzene mutase (CnbB), 2-aminophenol 1,6-dioxygenase (CnbCab), 2-amino-5-chloromuconic semialdehyde dehydrogenase (CnbD), 2-hydroxy-5-chloromuconic acid (2H5CM) tautomerase, and 2-amino-5-chloromuconic acid (2A5CM) deaminase (CnbH). In particular, the 2A5CM deaminase showed significant identities (31 to 38%) to subunit A of Asp-tRNA Asn /Glu-tRNA Gln amidotransferase and not to the previously identified deaminases for nitroaromatic compound degradation. Genetic cloning and expression of cnbH in Escherichia coli revealed that CnbH catalyzed the conversion of 2A5CM into 2H5CM and ammonium. Four other genes (cnbR, cnbE, cnbF, and cnbI) were tentatively identified according to their high sequence identities to other functionally identified genes. It was proposed that CnbH might represent a novel type of deaminase and be involved in a novel partial reductive pathway for chloronitrobenzene or nitrobenzene degradation.Chlorinated nitroaromatic compounds such as chloronitrobenzenes are massively produced and are widely used as intermediates for chemical syntheses of drugs, herbicides, dyes, etc. The natural formation of chlorinated nitroaromatic compounds is rare, and most of these compounds are from industrial productions and have been introduced into the environment for a relatively short period. Apparently, their occurrence in the environment has selected microorganisms that are able to utilize chlorinated nitroaromatic compounds as carbon and/or nitrogen sources for growth. Examples of such microorganisms are bacterial strain LW1 (15), a coculture of Pseudomonas putida and a Rhodococcus sp. (25), and recently Comamonas sp. strain CNB-1 (38).Nitroaromatic compounds and chlorinated nitroaromatic compounds are structurally analogs. The microbial degradation of nitroaromatic compounds has been extensively investigated and the removal of the nitro group(s) is carried out via oxidative pathways that initiate with monooxygenases (22, 31, 40) or dioxygenases (8,16,20,19,32) or a partial reductive pathway that initiates with nitroreductases (7-9, 17, 22, 29, 30). Although structurally related to the nitroaromatic compounds, the chlorinated nitroaromatic compounds are more resistant to microbial degradation due to the simultaneous existence of chlorine and nitro groups, and thus the knowledge of its microbial degradation is very limited.Previous studies revealed that reductive dehalogenization (35) and partial reduction of nitro groups (15, 39) might be involved in the initial steps during chlorina...

Due to their intrinsic safety, low cost, and ecofriendliness, aqueous Zn-ion batteries (ZIBs) have shown significant potential for wearable and flexible electronic devices. However, the lack of a stable and durable electrolyte for flexible ZIBs greatly hampers their applications in harsh conditions during daily use. In this work, we reported a stable hydrogel electrolyte, fabricated by coupling the grafted copolymer xanthan gum− polyacrylamide (XG−PAM) with cotton cellulose nanofiber (CNF), denoted XG−PAM/CNF. The designed XG−PAM/ CNF hydrogel electrolyte exhibited high ionic conductivity (28.8 mS cm −1 ), good adhesion, high mechanical strength, and strong ion adsorption. In addition, it also shows an inhibition effect on the generation of dendrites. The flexible ZIBs with the XG−PAM/CNF hydrogel electrolyte achieved high specific capacity (237 mA•h g −1 ) and excellent cycling stability (86.2% retention over 1000 cycles at 4 C). Notably, flexible ZIBs withstand severe conditions, such as bending, folding, poking, washing, soaking, and underwater usage. Furthermore, an underwater warning rescue system application was proposed. Consequently, this work provides a new approach and application for the development of reliable and durable wearable energy storage devices.

Novosphingobium taihuense sp. nov., a novel aromatic-compound-degrading bacterium isolated from Taihu Lake, China

Caves are typified by their permanent darkness and a shortage of nutrients. Consequently, bacteria play an important role in sustaining such subsurface ecosystems by dominating primary production and fueling biogeochemical cycles. China has one of the world’s largest areas of karst topography in the Yunnan-Guizhou Plateau, yet the bacteriomes in these karst caves remain unexplored. In this study, bacteriomes of eight karst caves in southwest China were examined, and co-occurrence networks of cave bacterial communities were constructed. Results revealed abundant and diversified bacterial communities in karst caves, with Proteobacteria , Actinobacteria , and Firmicutes being the most abundant phyla. Statistical analysis revealed no significant difference in bacteriomes among the eight caves. However, a PCoA plot did show that the bacterial communities of 128 cave samples clustered into groups corresponding to sampling types (air, water, rock, and sediment). These results suggest that the distribution of bacterial communities is driven more by sample types than the separate caves from which samples were collected. Further community-level composition analysis indicated that Proteobacteria were most dominant in water and air samples, while Actinobacteria dominated the sediment and rock samples. Co-occurrence analysis revealed highly modularized assembly patterns of the cave bacterial community, with Nitrosococcaceae wb1-P19, an uncultured group in Rokubacteriales , and an uncultured group in Gaiellales , being the top-three keystone members. These results not only expand our understanding of cave bacteriomes but also inspires functional exploration of bacterial strains in karst caves.

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BackgroundThe family Tetranychidae (Chelicerata: Acari) includes ~1200 species, many of which are of agronomic importance. To date, mitochondrial genomes of only two Tetranychidae species have been sequenced, and it has been found that these two mitochondrial genomes are characterized by many unusual features in genome organization and structure such as gene order and nucleotide frequency. The scarcity of available sequence data has greatly impeded evolutionary studies in Acari (mites and ticks). Information on Tetranychidae mitochondrial genomes is quite important for phylogenetic evaluation and population genetics, as well as the molecular evolution of functional genes such as acaricide-resistance genes. In this study, we sequenced the complete mitochondrial genome of Panonychus citri (Family Tetranychidae), a worldwide citrus pest, and provide a comparison to other Acari.ResultsThe mitochondrial genome of P. citri is a typical circular molecule of 13,077 bp, and contains the complete set of 37 genes that are usually found in metazoans. This is the smallest mitochondrial genome within all sequenced Acari and other Chelicerata, primarily due to the significant size reduction of protein coding genes (PCGs), a large rRNA gene, and the A + T-rich region. The mitochondrial gene order for P. citri is the same as those for P. ulmi and Tetranychus urticae, but distinctly different from other Acari by a series of gene translocations and/or inversions. The majority of the P. citri mitochondrial genome has a high A + T content (85.28%), which is also reflected by AT-rich codons being used more frequently, but exhibits a positive GC-skew (0.03). The Acari mitochondrial nad1 exhibits a faster amino acid substitution rate than other genes, and the variation of nucleotide substitution patterns of PCGs is significantly correlated with the G + C content. Most tRNA genes of P. citri are extremely truncated and atypical (44-65, 54.1 ± 4.1 bp), lacking either the T- or D-arm, as found in P. ulmi, T. urticae, and other Acariform mites.ConclusionsThe P. citri mitochondrial gene order is markedly different from those of other chelicerates, but is conserved within the family Tetranychidae indicating that high rearrangements have occurred after Tetranychidae diverged from other Acari. Comparative analyses suggest that the genome size, gene order, gene content, codon usage, and base composition are strongly variable among Acari mitochondrial genomes. While extremely small and unusual tRNA genes seem to be common for Acariform mites, further experimental evidence is needed.

CO hydrogenation to higher alcohols (C2+OH) provides a promising route to convert coal, natural gas, shale gas, and biomass feedstocks into value-added chemicals and transportation fuels. However, the development of nonprecious metal catalysts with satisfactory activity and well-defined selectivity toward C2+OH remains challenging and impedes the commercialization of this process. Here, we show that the synergistic geometric and electronic interactions dictate the activity of Cu0–χ-Fe5C2 binary catalysts for selective CO hydrogenation to C2+OH, outperforming silica-supported precious Rh-based catalysts, by using a combination of experimental evidence from bulk, surface-sensitive, and imaging techniques collected on real and high-performance Cu–Fe binary catalytic systems coupled with density functional theory calculations. The closer is the d-band center to the Fermi level of Cu0–χ-Fe5C2(510) surface than those of χ-Fe5C2(510) and Rh(111) surface, and the electron-rich interface of Cu0–χ-Fe5C2(510) due to the delocalized electron transfer from Cu0 atoms, facilitates CO activation and CO insertion into alkyl species to C2-oxygenates at the interface of Cu0–χ-Fe5C2(510) and thus enhances C2H5OH selectivity. Starting from the CHCO intermediate, the proposed reaction pathway for CO hydrogenation to C2H5OH on Cu0–χ-Fe5C2(510) is CHCO + (H) → CH2CO + (H) → CH3CO + (H) → CH3CHO + (H) → CH3CH2O + (H) → C2H5OH. This study may guide the rational design of high-performance binary catalysts made from earth-abundant metals with synergistic interactions for tuning selectivity.

The possible formation pathways of CH x (x = 1–3) and C–C chain involved in C2 oxygenate formation from syngas on an open Cu(110) surface have been systematically investigated to identify the preference mechanism of CH x (x = 1–3) and C–C chain formation. Here, we present the main results obtained from periodic density functional calculations. Our results show that all CH x (x = 1–3) species formation starts with CHO hydrogenation; among them, CH x (x = 2, 3) are the most favored monomers, however, CH3OH is the main product from syngas on the Cu(110) surface, and the formation of CH x (x = 1–3) cannot compete with CH3OH formation. Further, on the basis of the favored monomer CH x (x = 2, 3), we probe into the C–C chain formation of C2 oxygenates by CO or CHO insertion into CH x (x = 2, 3), as well as the hydrogenation, dissociation, and coupling of CH x (x = 2, 3), suggesting that CO insertion into CH2 to form C2 oxygenates is the dominant reaction for CH2 on the Cu(110) surface with an activation barrier of 44.5 kJ·mol–1; however, for CH3, CH3 hydrogenation to CH4 is the dominant reaction on the Cu(110) surface with an activation barrier of 67.5 kJ·mol–1. As a result, to achieve high productivity and selectivity for C2 oxygenates from syngas, Cu has to get help from the promoters, which should be able to boost CH2 formation and/or suppress CH3OH and CH3 formation. The present study provides the basis to understand and develop novel Cu-based catalysts for C2 oxygenate formation from syngas.