The recently published fourth Fermi Large Area Telescope source catalog (4FGL) a)b) , reports 5065 gamma-ray sources in terms of direct observational gamma-ray properties. Among the sources, the largest population is the Active Galactic Nuclei (AGN), which consists of 3137 blazars, 42 radio galaxies, and 28 other AGNs. The blazar sample comprises 694 flat-spectrum radio quasars (FSRQs), 1131 BL Lac-type objects (BL Lacs), and 1312 blazar candidates of an unknown type (BCUs). The classification of blazars is difficult using optical spectroscopy given the limited knowledge with respect to their intrinsic properties, and the limited availability of astronomical observations. To overcome these challenges, machine learning algorithms are being investigated as alternative approaches. Using the 4FGL catalog, a sample of 3137 Fermi blazars with 23 parameters is systematically selected. Three established supervised machine learning algorithms (random forests (RFs), support vector machines (SVMs), artificial neural networks (ANNs)) are employed to general predictive models to classify the BCUs. We analyze the results for all of the different combinations of parameters. Interestingly, a previously reported trend the use of more parameters leading to higher accuracy is not found. Considering the least number of parameters used, combinations of eight, 12 or 10 parameters in the SVM, ANN, or RF generated models achieve the highest accuracy (Accuracy ≃ 91.8%, or ≃ 92.9%). Using the combined classification results from the optimal combinations of parameters, 724 BL Lac type candidates and 332 FSRQ type candidates are predicted; however, 256 remain without a clear prediction.

In this paper, we have selected a sample of 64 teraelectronvolt blazars, with redshift, from those classified in the fourth Fermi Large Area Telescope source catalog. 3 3 https://fermi.gsfc.nasa.gov/ssc/data/access/lat/8yr_catalog/ We have obtained the values of the relevant physical parameters by performing a log-parabolic fitting of the average-state multiwavelength spectral energy distributions. We estimate the range of the radiation zone parameters, such as the Doppler factor (D), the magnetic field strength (B), the radiative zone radius (R), and the peak Lorentz factor (γ p) of nonthermal electrons. Here, we show that (1) there is a strong linear positive correlation between the intrinsic synchrotron peak frequency and the intrinsic inverse Compton scattering (ICs) peak frequency among different types of blazars; (2) if radio bands are excluded, the spectral index of each band is negatively correlated with the intrinsic peak frequency; (3) there is a strong linear negative correlation between the curvature at the peak and the intrinsic peak frequency of the synchrotron bump, and a weak positive correlation between the curvature at the peak and the intrinsic peak frequency of the ICs bump; (4) there is a strong linear positive correlation between the intrinsic ICs peak luminosity and intrinsic γ-ray luminosity and between the intrinsic ICs peak frequency and peak Lorentz factor; (5) there is a strong negative linear correlation between log B and log γ p ; and (6) there is no correlation between log R and log γ p .

In the fourth Fermi Large Area Telescope source catalog (4FGL), 5064 γ-ray sources are reported, including 3207 active galactic nuclei (AGNs), 239 pulsars, 1336 unassociated sources, 92 sources with weak association with blazars at low Galactic latitudes and 190 other sources. We employ two different supervised machine learning classifiers, combined with the direct observation parameters given by the 4FGL fits table, to search for sources potentially classified as AGNs and pulsars in the 1336 unassociated sources. In order to reduce the error caused by the large difference in the sizes of samples, we divide the classification process into two separate steps in order to identify the AGNs and the pulsars. First, we select the identified AGNs from all of the samples, and then select the identified pulsars from the remaining cases. Using the 4FGL sources associated or identified as AGNs, pulsars and other sources with the features selected through the K-S test and the random forest (RF) feature importance measurement, we trained, optimized and tested our classifier models. Then, the models are applied to classify the 1336 unassociated sources. According to the calculation results of the two classifiers, we report the sensitivity, specificity, accuracy in each step and the class of unassociated sources given by each classifier. The accuracy obtained in the first step is approximately 95%; in the second step, the obtained overall accuracy is approximately 80%. Combining the results of the two classifiers, we predict that there are 583 AGN-type candidates, 115 pulsar-type candidates, 154 other types of γ-ray candidates and 484 of uncertain types.

Cells use self-assembled biomaterials such as lipid membranes or proteinaceous shells to coordinate thousands of reactions that simultaneously take place within crowded spaces. However, mimicking such spatial organization for synthetic applications in engineered systems remains a challenge, resulting in inferior catalytic efficiency. In this work, we show that protein cages as an ideal scaffold to organize enzymes to enhance cascade reactions both in vitro and in living cells. We demonstrate that not only enzyme-enzyme distance but also the improved K m value contribute to the enhanced reaction rate of cascade reactions. Three sequential enzymes for lycopene biosynthesis have been co-localized on the exterior of the engineered protein cages in Escherichia coli, leading to an 8.5-fold increase of lycopene production by streamlining metabolic flux towards its biosynthesis. This versatile system offers a powerful tool to achieve enzyme spatial organization for broad applications in biocatalysis.

Two-component systems (TCS), which typically consist of a membrane-embedded histidine kinase and a cytoplasmic response regulator, are the dominant signaling proteins for transduction of environmental stimuli into cellular response pathways in prokaryotic cells. HptRSA is a recently identified TCS consisting of the G6P-associated sensor protein (HptA), transmembrane histidine kinase (HptS), and cytoplasmic effector (HptR). HptRSA mediates glucose-6-phosphate (G6P) uptake to supportStaphylococcus aureusgrowth and multiplication within various host cells. How the mechanism by which HptRSA perceives G6P and triggers a downstream response has remained elusive. Here, we solved the HptA structures in apo and G6P-bound states. G6P binding in the cleft between two HptA domains caused a conformational closing movement. The solved structures of HptA in complex with the periplasmic domain of HptS showed that HptA interacts with HptS through both constitutive and switchable interfaces. The G6P-free form of HptA binds to the membrane-distal side of the HptS periplasmic domain (HptSp), resulting in a parallel conformation of the HptSp protomer pair. However, once HptA associates with G6P, its intramolecular domain closure switches the HptA-HptSp contact region into the membrane-proximal domain, which causes rotation and closure of the C termini of each HptSp protomer. Through biochemical and growth assays of HptA and HptS mutant variants, we proposed a distinct mechanism of interface switch-mediated signaling transduction. Our results provide mechanistic insights into bacterial nutrient sensing and expand our understanding of the activation modes by which TCS communicates external signals.

The new entomopathogenic fungus Ophiocordyceps pingbianensis, collected from Southeast China, was described by mitogenomic, morphological, and phylogenetic evidence. The systematic position of O. pingbianensis was determined by phylogenetic analyses based on six nuclear gene (ITS, tef1-α, nrSSU, nrLSU, rpb1 and rpb2) and 14 mitochondrial protein-coding gene (PCGs) (cox1, cox2, cox3, atp6, atp8, atp9, cob, nad1, nad2, nad3, nad4, nad5, nad6 and nad4L) data. Phylogenetic analyses reveal that O. pingbianensis was belonged to the Hirsutella nodulosa clade in the genus Ophiocordyceps of Ophiocordycipiaceae. This fungus exhibits distinctive characteristics which differed from other related Ophiocordyceps species with slender and geminate stromata, monophialidic conidiogenous cells with an inflated awl-shaped base, a twisty and warty phialide neck and a fusiform or oval conidia, as well as being found on a tiger beetle of Coleoptera buried in moss at the cave. The complete mitochondrial genome of O. pingbianensis was a circular DNA molecule 80,359 bp in length, containing 15 PCGs, 24 open reading frames genes (ORFs), 25 transfer RNA genes (tRNAs) and 27 introns. Ophiocordyceps pingbianensis, containing 27 introns, has the second largest mitogenome in Ophiocordycipiaceae and was next to O. sinensis. To our knowledge, this is the first report of the mitogenome from a new entomopathogenic fungus, and thus provides an important foundation for future studies on taxonomy, genetics and evolutionary biology of Ophiocordycipiaceae.

The next generation of TeV detectors is expected to have significantly enhanced performance. It is therefore constructive to search for new TeV candidates for observation. This paper focuses on TeV candidates among the high-synchrotron-peaked BL Lacertae objects (HBLs) reported in the fourth catalog of active galactic nuclei detected by Fermi’s Large Area Telescope, i.e., 4LAC. By cross-matching the Fermi data with radio and optical observations, we collected the multiwavelength features of 180 HBLs with known redshifts. The data set contains 39 confirmed TeV sources and 141 objects whose TeV detection has not yet been reported (either not yet observed, or observed but not detected). Using two kinds of supervised machine-learning (SML) methods, we searched for new possible TeV candidates (PTCs) among the nondetected objects by assessing the similarity of their multi-wavelength properties to existing TeV-detected objects. The classification results of the two SML classifiers were combined and the 24 highest-confidence PTCs were proposed as the best candidates. We calculate, here, the 12 year averaged Fermi spectra of these PTCs and estimate their detectability by extrapolating the Fermi spectra and including the extragalactic background light attenuation. Four candidates are suggested to have a high likelihood of being detected by the Large High Altitude Air Shower Observatory, and 24 are candidates for Cherenkov Telescope Array observations.

The mycoparasite fungi of Clonostachys have contributed to the biological control of plant fungal disease and nematodes. The Clonostachys fungi strains were isolated from Ophiocordyceps highlandensis, Ophiocordycepsnigrolla and soil, which identified as Clonostachyscompactiuscula, Clonostachysrogersoniana, Clonostachyssolani and Clonostachys sp. To explore the evolutionary relationship between the mentioned species, the mitochondrial genomes of four Clonostachys species were sequenced and assembled. The four mitogenomes consisted of complete circular DNA molecules, with the total sizes ranging from 27,410 bp to 42,075 bp. The GC contents, GC skews and AT skews of the mitogenomes varied considerably. Mitogenomic synteny analysis indicated that these mitogenomes underwent gene rearrangements. Among the 15 protein-coding genes within the mitogenomes, the nad4L gene exhibited the least genetic distance, demonstrating a high degree of conservation. The selection pressure analysis of these 15 PCGs were all below 1, indicating that PCGs were subject to purifying selection. Based on protein-coding gene calculation of the significantly supported topologies, the four Clonostachys species were divided into a group in the phylogenetic tree. The results supplemented the database of mitogenomes in Hypocreales order, which might be a useful research tool to conduct a phylogenetic analysis of Clonostachys. Additionally, the suitable molecular marker was significant to study phylogenetic relationships in the Bionectriaceae family.