Volatile metabolites profiling of a Chinese mangrove endophytic Pestalotiopsis sp. strain

Pestalotiopsis JCM2A4, an endophytic fungus originally isolated from leaves of the Chinese mangrove plant Rhizophora mucronata, produces a mixture of volatile metabolites. As determined by gas chromatography and gas chromatography/mass spectrometry (GC/GC-MS), 18 compounds representing all of the hexane extract were identified. Higher amounts of oil-based straight-chained alkyl (mono- and di-methyl) esters and fatty acids were found to compose major volatile chemotype which accounted for 78.65 and 14.52% of this organism, respectively. The main components was demonstrated to be pentadecanoic acid, 14-methyl-, methyl ester (35.92%); octadecanoic acid, methyl ester (13.10%); nonanedioic acid, dimethyl ester (11.21%); and n-hexadecanoic acid (10.54%). Two of these components were isolated and determined to be n-hexadecanoic acid and elaidic acid by 1H NMR and 1H-1H COSY spectroscopy. Antioxidant activity of the hexane extract and isolated compounds were screened using 2,2'-diphenyl-b-picrylhydrazyl (DPPH) free radical scavenging method. This is the first report to describe the volatile metabolites of mangrove endophytic Pestalotiopsis sp. strain; its specific fatty acid methyl esters (FAME) profile can be used as a tool for microbial source tracking.Keywords: Mangrove endophytic fungus, Pestalotiopsis sp., volatile metabolites, fatty acid methyl esters (FAME) profileAfrican Journal of Biotechnology Vol. 12(24), pp. 3802-380

Crystal Structure of the Cysteine Desulfurase DndA from Streptomyces lividans Which Is Involved in DNA Phosphorothioation

DNA phosphorothioation is widespread among prokaryotes, and might function to restrict gene transfer among different kinds of bacteria. There has been little investigation into the structural mechanism of the DNA phosphorothioation process. DndA is a cysteine desulfurase which is involved in the first step of DNA phosphorothioation. In this study, we determined the crystal structure of Streptomyces lividans DndA in complex with its covalently bound cofactor PLP, to a resolution of 2.4 Å. Our structure reveals the molecular mechanism that DndA employs to recognize its cofactor PLP, and suggests the potential binding site for the substrate L-cysteine on DndA. In contrast to previously determined structures of cysteine desulfurases, the catalytic cysteine of DndA was found to reside on a β strand. This catalytic cysteine is very far away from the presumable location of the substrate, suggesting that a conformational change of DndA is required during the catalysis process to bring the catalytic cysteine close to the substrate cysteine. Moreover, our in vitro enzymatic assay results suggested that this conformational change is unlikely to be a simple result of random thermal motion, since moving the catalytic cysteine two residues forward or backward in the primary sequence completely disabled the cysteine desulfurase activity of DndA

Sciences for The 2.5-meter Wide Field Survey Telescope (WFST)

The Wide Field Survey Telescope (WFST) is a dedicated photometric survey facility under construction jointly by the University of Science and Technology of China and Purple Mountain Observatory. It is equipped with a primary mirror of 2.5m in diameter, an active optical system, and a mosaic CCD camera of 0.73 Gpix on the main focus plane to achieve high-quality imaging over a field of view of 6.5 square degrees. The installation of WFST in the Lenghu observing site is planned to happen in the summer of 2023, and the operation is scheduled to commence within three months afterward. WFST will scan the northern sky in four optical bands (u, g, r, and i) at cadences from hourly/daily to semi-weekly in the deep high-cadence survey (DHS) and the wide field survey (WFS) programs, respectively. WFS reaches a depth of 22.27, 23.32, 22.84, and 22.31 in AB magnitudes in a nominal 30-second exposure in the four bands during a photometric night, respectively, enabling us to search tremendous amount of transients in the low-z universe and systematically investigate the variability of Galactic and extragalactic objects. Intranight 90s exposures as deep as 23 and 24 mag in u and g bands via DHS provide a unique opportunity to facilitate explorations of energetic transients in demand for high sensitivity, including the electromagnetic counterparts of gravitational-wave events detected by the second/third-generation GW detectors, supernovae within a few hours of their explosions, tidal disruption events and luminous fast optical transients even beyond a redshift of 1. Meanwhile, the final 6-year co-added images, anticipated to reach g about 25.5 mag in WFS or even deeper by 1.5 mag in DHS, will be of significant value to general Galactic and extragalactic sciences. The highly uniform legacy surveys of WFST will also serve as an indispensable complement to those of LSST which monitors the southern sky.Comment: 46 pages, submitted to SCMP

Eight-Element Communication Model for Internet Health Rumors: A New Exploration of Lasswell’s “5W Communication Model”

(1) Background: Rumors are a special type of information. Based on the classic theory of the communication of information, the “5W” communication model, this article aims to build a new model and thus explains the generation and communication of Internet health rumors. (2) Methods: The authors selected 50 Internet health rumors, which were widely spread in widely used websites and social media in China, then grounded theory is used to perform the qualitative analysis of the Internet health rumors. (3) Results: Three Core Concepts are abstracted after qualitative analysis. An internal dynamic mutual assistance mechanism of the communication of rumors is built and illustrated. Based on Lasswell’s “5W” communication model, the authors develop an eight-element communication model for Internet health rumors to illustrate the generation and communication of Internet health rumors. (4) Conclusions: By removing one or several elements of this new model, the chain of the communication of Internet health rumors could be cut off, which is valuable information for the government or websites to manage communication of Internet health rumors