Distinct colonization patterns and cDNA-AFLP transcriptome profiles in compatible and incompatible interactions between melon and different races of Fusarium oxysporum f. sp. melonis

Background: Fusarium oxysporum f. sp. melonis Snyd. & Hans. (FOM) causes Fusarium wilt, the most important infectious disease of melon (Cucumis melo L.). The four known races of this pathogen can be distinguished only by infection on appropriate cultivars. No molecular tools are available that can discriminate among the races, and the molecular basis of compatibility and disease progression are poorly understood. Resistance to races 1 and 2 is controlled by a single dominant gene, whereas only partial polygenic resistance to race 1,2 has been described. We carried out a large-scale cDNA-AFLP analysis to identify host genes potentially related to resistance and susceptibility as well as fungal genes associated with the infection process. At the same time, a systematic reisolation procedure on infected stems allowed us to monitor fungal colonization in compatible and incompatible host-pathogen combinations. Results: Melon plants (cv. Charentais Fom-2), which are susceptible to race 1,2 and resistant to race 1, were artificially infected with a race 1 strain of FOM or one of two race 1,2 w strains. Host colonization of stems was assessed at 1, 2, 4, 8, 14, 16, 18 and 21 days post inoculation (dpi), and the fungus was reisolated from infected plants. Markedly different colonization patterns were observed in compatible and incompatible host-pathogen combinations. Five time points from the symptomless early stage (2 dpi) to obvious wilting symptoms (21 dpi) were considered for cDNA-AFLP analysis. After successful sequencing of 627 transcript-derived fragments (TDFs) differentially expressed in infected plants, homology searching retrieved 305 melon transcripts, 195 FOM transcripts expressed in planta and 127 orphan TDFs. RNA samples from FOM colonies of the three strains grown in vitro were also included in the analysis to facilitate the detection of in planta-specific transcripts and to identify TDFs differentially expressed among races/strains. Conclusion: Our data suggest that resistance against FOM in melon involves only limited transcriptional changes, and that wilting symptoms could derive, at least partially, from an active plant response. We discuss the pathogen-derived transcripts expressed in planta during the infection process and potentially related to virulence functions, as well as transcripts that are differentially expressed between the two FOM races grown in vitro. These transcripts provide candidate sequences that can be further tested for their ability to distinguish between races. Sequence data from this article have been deposited in GenBank, Accession Numbers: HO867279-HO867981

Identification and characterization of antibacterial compound(s) of cockroaches (Periplaneta americana)

Infectious diseases remain a significant threat to human health, contributing to more than 17 million deaths, annually. With the worsening trends of drug resistance, there is a need for newer and more powerful antimicrobial agents. We hypothesized that animals living in polluted environments are potential source of antimicrobials. Under polluted milieus, organisms such as cockroaches encounter different types of microbes, including superbugs. Such creatures survive the onslaught of superbugs and are able to ward off disease by producing antimicrobial substances. Here, we characterized antibacterial properties in extracts of various body organs of cockroaches (Periplaneta americana) and showed potent antibacterial activity in crude brain extract against methicillin-resistant Staphylococcus aureus and neuropathogenic E. coli K1. The size-exclusion spin columns revealed that the active compound(s) are less than 10 kDa in molecular mass. Using cytotoxicity assays, it was observed that pre-treatment of bacteria with lysates inhibited bacteria-mediated host cell cytotoxicity. Using spectra obtained with LC-MS on Agilent 1290 infinity liquid chromatograph, coupled with an Agilent 6460 triple quadruple mass spectrometer, tissues lysates were analyzed. Among hundreds of compounds, only a few homologous compounds were identified that contained isoquinoline group, chromene derivatives, thiazine groups, imidazoles, pyrrole containing analogs, sulfonamides, furanones, flavanones, and known to possess broad-spectrum antimicrobial properties, and possess anti-inflammatory, anti-tumour, and analgesic properties. Further identification, characterization and functional studies using individual compounds can act as a breakthrough in developing novel therapeutics against various pathogens including superbugs

Spatially resolved model of oxygen reduction reaction in silver based porous gas diffusion electrodes based on operando measurements

An improved spatially resolved mathematical model for porous, silver based gas diffusion electrodes for the oxygen reduction reaction in strongly alkaline electrolyte is presented. For the first time, important parameters describing the distribution of the liquid electrolyte in the electrode were determined via inde pendent operando synchrotron experiments. With the model, a reasonable description of the overvoltage as a function of the current density at 80 C could be achieved in a range of electrolyte concentrations 27 36.6 wt. NaOH and oxygen contents 20 100 vol. . Model based analysis of the processes in side the electrode revealed that a complex water cycle evolves which supports the removal of hydroxide ions and thus boosts the electrode performance. The analysis also showed that additional operando mea surement of the electrolyte distribution and investigations with electrodes having a defined thickness of the reaction layer will help to further improve the mode

Operando Laboratory X Ray Imaging of Silver Based Gas Diffusion Electrodes during Oxygen Reduction Reaction in Highly Alkaline Media

Operando laboratory X ray radiographies were carried out for imaging of two di erent silver based gas di usion electrodes containing an electroconductive Ni mesh structure, one gas di usion electrode composed of 95 wt. Ag and 5 wt. polytetrafluoroethylene and one composed of 97 wt. Ag and 3 wt. polytetrafluoroethylene, under di erent operating parameters. Thereby, correlations of their electrochemical behavior and the transport of the 30 wt. NaOH electrolyte through the gas di usion electrodes were revealed. The work was divided into two parts. In the first step, the microstructure of the gas di usion electrodes was analyzed ex situ by a combination of focused ion beam technology and synchrotron as well as laboratory X ray tomography and radiography. In the second step, operando laboratory X ray radiographies were performed during chronoamperometric measurements at di erent potentials. The combination of the ex situ microstructural analyses and the operando measurements reveals the impact of the microstructure on the electrolyte transport through the gas di usion electrodes. Hence, an impact of the Ni mesh structure within the gas di usion electrode on the droplet formation could be shown. Moreover, it could be observed that increasing overpotentials cause increasing electrolyte transport velocities and faster droplet formation due to electrowetting. In general, higher electrolyte transport velocities were found for the gas di usion electrode with 97 wt. Ag in contrast to that with 95 wt. A

Operando Synchrotron Imaging of Electrolyte Distribution in Silver Based Gas Diffusion Electrodes During Oxygen Reduction Reaction in Highly Alkaline Media

Understanding how gas diffusion electrodes are working is crucial to improve their performance and cost efficiency. One key issue is the electrolyte distribution during operation. Here, operando synchrotron imaging of the electrolyte distribution in silver based gas diffusion electrodes is presented. For this purpose, a half cell compartment was designed for operando synchrotron imaging of chronoamperometric measurements. For the first time, the electrolyte distribution could be analyzed in real time 1 s time resolution even in individual pores as small as a few micrometers. The detailed analyses of dynamic filling processes are an important step for understanding and improving electrode

Development of a Modular Operando Cell for X ray Imaging of Strongly Absorbing Silver Based Gas Diffusion Electrodes

Metal based gas diffusion electrodes are utilized in chlor alkali electrolysis or electrochemical reduction of carbon dioxide, allowing the reaction to proceed at high current densities. In contrast to planar electrodes and predominantly 2D designs, the industrially required high current densities can be achieved by intense contact between the gas and liquid phase with the catalytically active surfaces. An essential asset for the knowledge based design of tailored electrodes is therefore in depth information on electrolyte distribution and intrusion into the electrode s porous structure. Lab based and synchrotron radiography allow for monitoring this process operando. Herein, we describe the development of a cell design that can be modularly adapted and successfully used to monitor both the oxygen reduction reaction and the electrochemical reduction of CO2 as exemplary and currently very relevant examples of gas liquid reactions by only minor modifications to the cell set up. With the reported cell design, we were able to observe the electrolyte distribution within the gas diffusion electrode during cell operation in realistic condition