Identification of ClpP Dual Isoform Disruption as an Anti-sporulation Strategy for Clostridioides difficile

The Gram-positive bacterium Clostridioides difficile is a primary cause of hospital-acquired diarrhea, threatening both immunocompromised and healthy individuals. An important aspect of defining mechanisms that drive C. difficile persistence and virulence relies on developing a more complete understanding of sporulation. C. difficile sporulation is the single determinant of transmission and complicates treatment and prevention due to the chemical and physical resilience of spores. By extension, the identification of druggable targets that significantly attenuate sporulation would have a significant impact on thwarting C. difficile infection. Using a new CRISPR-Cas9 nickase genome editing methodology, stop codons were inserted early in the coding sequence for clpP1 and clpP2 to generate C. difficile mutants that no longer produced the corresponding isoforms of caseinolytic protease P (ClpP). The data show that genetic ablation of ClpP isoforms leads to altered sporulation phenotypes with the clpP1/clpP2 double mutant exhibiting asporogenic behavior. A small screen of known ClpP inhibitors in a fluorescence-based biochemical assay identified bortezomib as an inhibitor of C. difficile ClpP that produces dose-dependent inhibition of purified ClpP. Incubation of C. difficile cultures in the presence of bortezomib reveals anti-sporulation effects approaching that observed in the clpP1/clpP2 double mutant. This work identifies ClpP as a key contributor to C. difficile sporulation and provides compelling support for the pursuit of small molecule ClpP inhibitors as C. difficile anti-sporulating agents. IMPORTANCE Due to diverse roles of ClpP and the reliance of pathogens upon this system for infection, it has emerged as a target for antimicrobial development. Biology regulated by ClpP is organism-dependent and has not been defined in C. difficile . This work identifies ClpP as a key contributor to C. difficile sporulation and provides compelling support for the pursuit of small molecule ClpP inhibitors as anti-sporulating agents. The identification of new approaches and/or drug targets that reduce C. difficile sporulation would be transformative and are expected to find high utility in prophylaxis, transmission attenuation, and relapse prevention. Discovery of the ClpP system as a major driver to sporulation also provides a new avenue of inquiry for advancing the understanding of sporulation.

All-Fiber Gas Cavity Based on Anti-Resonant Hollow-Core Fibers Fabricated by Splicing with End Caps

In recent years, fiber gas lasers have obtained a rapid development, however, efficient and stable pump coupling is a key limitation for their applications in the future. Here, we report an all-fiber gas cavity based on anti-resonant hollow-core fibers which have the beneficial properties of adjustable broad transmission bands and potential low transmission attenuation, especially in the mid-infrared. This kind of all-fiber gas cavity is fabricated by directly splicing with end caps at both ends for the first time. The high-power laser transmission characteristics were studied, and the experimental results show that the all-fiber gas cavities have a very stable performance. The maximum input laser power at 1080 nm is about 260 W, and the output power is 203 W, giving a total transmission efficiency of 78.1%. This work opens a new opportunity for the development of high-power all-fiber structured fiber gas lasers.

Research on a simulating device for electric transmission characteristics of long-distance subsea umbilical cable

Subsea umbilical cable is an important link to transmit power and signals in subsea production system, often lasts for tens of kilometers in deep-sea projects. It is expensive, bulky, and inconvenient to transport. In this article, a compact, low-cost umbilical cable electrical simulator is proposed, which can be equivalent to the real umbilical cable in power transmission characteristics and can adjust parameters in a certain range. By studying the electrical transmission characteristics of long umbilical cable, the calculation method of electrical transmission characteristics is determined. A simulation device for simulating the transmission characteristics of umbilical cable is designed, which can be used to simulate the umbilical cable diameter of 10 and 16 mm2. The voltage drop characteristics, signal transmission attenuation characteristics, and power carrier characteristics of the umbilical cable electrical simulation device are simulated and experimentally analyzed. The experimental results show that the voltage drop characteristics, signal transmission attenuation characteristics, and power carrier characteristics of the umbilical cable electrical simulator are in good agreement with the real umbilical cable. The simulation device of umbilical cable can well simulate the power and signal transmission characteristics of real umbilical cable.

Transmission Attenuation Power Ratio Analysis of Flexible Electromagnetic Absorber Sheets Combined with a Metal Layer

Electromagnetic noise absorber sheets have become a solution for solving complex electromagnetic interference (EMI) problems due to their high magnetic losses. This contribution is focused on characterizing a novel structure that is based on an absorber film with a metal layer attached on its top side. Two different absorber compositions were combined with Al and Cu metal layers in order to study the improvement on the performance of these structures, depending on the complex permeability, absorber film thickness, and type of metal. The transmission attenuation power ratio of the absorber films is analyzed and compared to the performance of absorber and metal structures. The measurement procedure is carried out attaching the films into a microstrip line that has been designed based on IEC standard (IEC 62333-2). This test fixture is employed as a transmission line to simulate a general noise path. The performance of absorber composites to filter electromagnetic noise is evaluated through analyzing S21 and S11 parameters. This is carried out with the aim of finding out in which conditions the absorption loss is improved when a metal layer is attached. In addition, the possible re-radiation effect, due to the magnetic field that is generated by the eddy currents induced in the metal layer, is examined.