Chung-Ang University

About: Chung-Ang University is a education organization based out in Seoul, South Korea. It is known for research contribution in the topics: Population & Thin film. The organization has 13381 authors who have published 26978 publications receiving 416735 citations. The organization is also known as: CAU & Chung.

Freshwater viral metagenome reveals novel and functional phage-borne antibiotic resistance genes

Abstract: Antibiotic resistance developed by bacteria is a significant threat to global health. Antibiotic resistance genes (ARGs) spread across different bacterial populations through multiple dissemination routes, including horizontal gene transfer mediated by bacteriophages. ARGs carried by bacteriophages are considered especially threatening due to their prolonged persistence in the environment, fast replication rates, and ability to infect diverse bacterial hosts. Several studies employing qPCR and viral metagenomics have shown that viral fraction and viral sequence reads in clinical and environmental samples carry many ARGs. However, only a few ARGs have been found in viral contigs assembled from metagenome reads, with most of these genes lacking effective antibiotic resistance phenotypes. Owing to the wide application of viral metagenomics, nevertheless, different classes of ARGs are being continuously found in viral metagenomes acquired from diverse environments. As such, the presence and functionality of ARGs encoded by bacteriophages remain up for debate. We evaluated ARGs excavated from viral contigs recovered from urban surface water viral metagenome data. In virome reads and contigs, diverse ARGs, including polymyxin resistance genes, multidrug efflux proteins, and β-lactamases, were identified. In particular, when a lenient threshold of e value of ≤ 1 × e−5 and query coverage of ≥ 60% were employed in the Resfams database, the novel β-lactamases blaHRV-1 and blaHRVM-1 were found. These genes had unique sequences, forming distinct clades of class A and subclass B3 β-lactamases, respectively. Minimum inhibitory concentration analyses for E. coli strains harboring blaHRV-1 and blaHRVM-1 and catalytic kinetics of purified HRV-1 and HRVM-1 showed reduced susceptibility to penicillin, narrow- and extended-spectrum cephalosporins, and carbapenems. These genes were also found in bacterial metagenomes, indicating that they were harbored by actively infecting phages. Our results showed that viruses in the environment carry as-yet-unreported functional ARGs, albeit in small quantities. We thereby suggest that environmental bacteriophages could be reservoirs of widely variable, unknown ARGs that could be disseminated via virus-host interactions.

Oxygen‐Independent Decarbonylation of Aldehydes by Cyanobacterial Aldehyde Decarbonylase: A New Reaction of Diiron Enzymes

Abstract: The search for new biofuels has generated increased interest in biochemical pathways that produce hydrocarbons.[1] Although hydrocarbons are simple molecules, the biosynthesis of molecules that lack any chemical functional groups is surprisingly challenging.[2] Biochemical reactions that remove functionality, such as decarboxylations, dehydrations and reduction of double bonds, invariably rely on the presence of adjacent functional groups to stabilize unfavorable transition states. Enzymes involved in hydrocarbon biosynthesis are therefore of interest both for applications in biofuels production and because of the unusual and chemically difficult reactions they catalyze.[3] One enzyme that has attracted particular interest, is aldehyde decarbonylase (AD), which catalyzes the decarbonylation of long-chain fatty aldehydes, to the corresponding alkanes.[4]

Local Well-Posedness for the Hall-MHD Equations with Fractional Magnetic Diffusion

Abstract: The Hall-magnetohydrodynamics (Hall-MHD) equations, rigorously derived from kinetic models, are useful in describing many physical phenomena in geophysics and astrophysics. This paper studies the local well-posedness of classical solutions to the Hall-MHD equations with the magnetic diffusion given by a fractional Laplacian operator, (−Δ) α .D ue to the presence of the Hall term in the Hall-MHD equations, standard energy estimates appear to indicate that we need α ≥ 1 in order to obtain the local well-posedness. This paper breaks the barrier and shows that the fractional Hall-MHD equations are locally well-posed for any α> 1 . The approach here fully exploits the smoothing effects of the dissipation and establishes the local bounds for the Sobolev norms through the Besov space techniques. The method presented here may be applicable to similar situations involving other partial differential equations.