Cyclic ADP ribose (cADPR) isomers are signaling molecules produced by bacterial and plant Toll/interleukin-1 receptor (TIR) domains via NAD + hydrolysis. We show that v-cADPR (2′cADPR) and v2-cADPR (3′cADPR) isomers are cyclized by O -glycosidic bond formation between the ribose moieties in ADPR. Structures of 2′cADPR-producing TIR domains reveal conformational changes leading to an active assembly that resembles those of Toll-like receptor adaptor TIR domains. Mutagenesis reveals a conserved tryptophan essential for cyclization. We show that 3′cADPR is an activator of ThsA effector proteins from bacterial anti-phage defense systems termed Thoeris, and a suppressor of plant immunity when produced by the effector HopAM1. Collectively, our results reveal the molecular basis of cADPR isomer production and establish 3′cADPR in bacteria as an antiviral and plant immunity-suppressing signaling molecule.

Exploring highly efficient and cost-effective electrocatalysts with more feasible synthesis strategies toward oxygen evolution reaction (OER) is highly desirable for a broad range of advanced sustainable energy conversion systems. Herein, we develop a feasible electrospinning strategy for the facile fabrication of a Co 3 O 4 /CeO 2 heterostructure in situ embedded in N-doped carbon nanofibers (h-Co 3 O 4 /CeO 2 @N-CNFs) as a high-performance electrocatalyst for the OER. Unlike previously reported Co 3 O 4 /CeO 2 composites, the as-prepared Co 3 O 4 /CeO 2 heterostructure presents hollow and porous features. The nanopores can develop within Co 3 O 4 /CeO 2 nanocrystals with an analogous mechanism to void formation in the Kirkendall effect. Electrochemical measurements demonstrate that h-Co 3 O 4 /CeO 2 @N-CNFs can enable high OER activity with a low overpotential of 310 mV to achieve 10 mA cm −2 current density and good stability that can maintain 40 000 s without perceptible attenuation, outperforming those of the commercial RuO 2 catalyst. The outstanding OER performance originates from the important synergies by combining hollow Co 3 O 4 /CeO 2 heterostructures and three-dimensional porous N-CNF networks.

Exploring cost‐effective and high‐performance bifunctional electrocatalysts for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is of paramount importance for the advancement of H2 production technology, yet remains a huge challenge. Herein, a simple electrospinning–pyrolysis strategy is developed to directly immobilize uniform Ni3Co nanoparticles into a hierarchical branched architecture constructed by in situ formed N‐doped carbon‐nanotube‐grafted carbon nanofibers. The elaborate construction of such hybrid hierarchical architecture can effectively modulate the electronic structure of the active sites, enlarge the exposure of active sites, and facilitate the electron transfer and mass diffusion, favoring both the HER and OER. As a result, the optimized catalyst requires relatively low overpotentials of 114 and 243 mV for HER and OER, respectively, to deliver a current density of 10 mA cm−2 in 0.1 m KOH electrolyte. When employed as a bifunctional catalyst for overall water splitting, the resultant catalyst shows a low cell voltage of 1.57 V to achieve a current density of 10 mA cm−2, along with an impressive stability without noticeable attenuation even after 27 h. This work presents a successful demonstration in optimizing the electrocatalytic performance of Ni‐based bifunctional electrocatalysts by simultaneously considering modulation of electronic structure, hybridization with carbon substrate, and nanostructuring through a facile synthetic strategy, which provides a new avenue to the design of a rich variety of robust transition‐metal‐based electrocatalysts for large‐scale water electrolysis.

Denitrifying bacteria is a driver of nitrogen removal process in wastewater treatment ecosystem. However, the geographical characteristics of denitrifying bacterial communities associated with activated sludge from diverse wastewater treatment plants (WWTPs) are still unclear. Here, quantitative PCR and next-generation sequencing of the nirS gene were applied to characterize the abundance and denitrifying bacterial communities from 18 geographically distributed WWTPs. The results showed that the nirS abundance ranged from 4.6 × 10 to 2.4 × 10 copies per ng DNA, while nirS-type denitrifying bacterial populations were diverse and distinct from activated sludge communities. Among WWTPs, total nitrogen removal efficiencies varied from 25.8 to 84%, which was positively correlated with diversity indices, whereas abundance-based coverage estimator index decreased with an increase in latitude. The dominant phyla across all samples were proteobacteria, accounting for 46.23% (ranging from 17.98 to 87.07%) of the sequences. Eight of the 22 genera detected were dominant: Thauera sp., Alicycliphilus sp., and Pseudomonas sp., etc. Based on network analysis, the coexistence and interaction between dominant genera may be vital for regulating the nitrogen and carbon removal behaviors. Multivariate statistical analysis revealed that both geographic location and wastewater factors concurrently govern the distribution patterns of nirS-type denitrifying bacterial community harbored in WWTPs. Taking together, these results from the present study provide novel insights into the nirS gene abundance and nirS-type denitrifying bacterial community composition in geographically distributed WWTPs. Moreover, the knowledge gained will improve the operation and management of WWTPs for nitrogen removal.

The microbial communities associated with algal blooms play a pivotal role in organic carbon, nitrogen and phosphorus cycling in freshwater ecosystems. However, there have been few studies focused on unveiling the dynamics of bacterial and fungal communities during the outbreak and decline of algal blooms in drinking water reservoirs. To address this issue, the compositions of bacterial and fungal communities were assessed in the Zhoucun drinking water reservoir using 16S rRNA and internal transcribed spacer (ITS) gene Illumina MiSeq sequencing techniques. The results showed the algal bloom was dominated by Synechococcus, Microcystis, and Prochlorothrix. The bloom was characterized by a steady decrease of total phosphorus (TP) from the outbreak to the decline period (p < 0.05) while Fe concentration increased sharply during the decline period (p < 0.05). The highest algal biomass and cell concentrations observed during the bloom were 51.7 mg/L and 1.9×108 cell/L, respectively. The cell concentration was positively correlated with CODMn (r = 0.89, p = 0.02). Illumina Miseq sequencing showed that algal bloom altered the water bacterial and fungal community structure. During the bloom, the dominant bacterial genus were Acinetobacter sp., Limnobacter sp., Synechococcus sp., and Roseomonas sp. The relative size of the fungal community also changed with algal bloom and its composition mainly contained Ascomycota, Basidiomycota and Chytridiomycota. Heat map profiling indicated that algal bloom had a more consistent effect upon fungal communities at genus level. Redundancy analysis (RDA) also demonstrated that the structure of water bacterial communities was significantly correlated to conductivity and ammonia nitrogen. Meanwhile, water temperature, Fe and ammonia nitrogen drive the dynamics of water fungal communities. The results from this work suggested that water bacterial and fungal communities changed significantly during the outbreak and decline of algal bloom in Zhoucun drinking water reservoir. Our study highlights the potential role of microbial diversity as a driving force for the algal bloom and biogeochemical cycling of reservoir ecology.

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Toll/interleukin-1 receptor (TIR) domain proteins function in cell death and immunity. In plants and bacteria, TIR domains are enzymes that produce isomers of cyclic ADPR (cADPR) as putative immune signaling molecules. The identity and functional conservation of cADPR isomer signals is unclear. A previous report found that a plant TIR could cross activate the prokaryotic Thoeris TIR-immune system, suggesting the conservation of plant and prokaryotic TIR-immune signals. Here, we generate auto-active Thoeris TIRs and test the converse hypothesis: do prokaryotic Thoeris TIRs also cross-activate plant TIR immunity? Using in planta and in vitro assays, we find that Thoeris and plant TIRs generate overlapping sets of cADPR isomers, and further clarify how plant and Thoeris TIRs activate the Thoeris system via producing 3'cADPR. This study demonstrates that the TIR-signaling requirements for plant and prokaryotic immune systems are distinct and that TIRs across kingdoms generate a diversity of small molecule products.

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