1,720,987 research outputs found
Study of the Effect of Water Pressure on Plasma and Cavitation Bubble Induced by Pulsed Laser Ablation in Liquid of Silver and Missed Variations of Observable Nanoparticle Features
No full textIn this work the effects of the pressure between 1–150 Bar on pulsed laser ablation in liquids (PLAL) during the production of silver nanoparticles (AgNPs) in water was investigated. The produced NPs are the results of two different well-known stages which are the plasma and the bubble evolution occurring until the generated material is released into the solution. The main aim of this work is to show which roles is played by the variation of water pressure on the laser induced plasma and the cavitation bubble dynamics during the NPs formation. Their implication on the comprehension of the as-produced NPs formation mechanisms is treated. The typical timescales of the different stages occurring in water at different pressures have been studied by optical emission spectroscopy (OES), imaging and shadowgraph experiments. Finally surface plasmon resonance (SPR) spectroscopy, transmission electron microscopy (TEM), dynamic light scattering (DLS) and scanning electron microscopy (SEM) for characterization of the material released in solution, have been used
Basidiomycetes are particularly sensitive to bacterial volatile compounds: mechanistic insight into the case study of Pseudomonas protegens volatilome against Heterobasidion abietinum
No full textVolatile organic compounds (VOCs) play an important role in the communication among organisms, including plants, beneficial or pathogenic microbes, and pests. In vitro, we observed that the growth of seven out of eight Basidiomycete species tested was inhibited by the VOCs of the biocontrol agent Pseudomonas protegens strain CHA0. In the Ascomycota phylum, only some species were sensitive (e.g., Sclerotinia sclerotiorum, Botrytis cinerea, etc.) but others were resistant (e.g., Fusarium oxysporum f. sp. cubense, Verticillium dahliae, etc.). We further discovered that CHA0 as well as other ten beneficial or phytopathogenic bacterial strains were all able to inhibit Heterobasidion abietinum, which was used in this research as a model species. Moreover, such an inhibition occurred only when bacteria grew on media containing digested proteins like peptone or tryptone (e.g., Luria-Bertani agar or LBA). Also, the inhibition co-occurred with a pH increase of the agar medium where the fungus grew. Therefore, biogenic ammonia originating from protein degradation by bacteria was hypothesized to play a major role in fungus inhibition. Indeed, when tested as a synthetic compound, it was highly toxic to H. abietinum (effective concentration 50% or EC50 = 1.18 M; minimum inhibitory concentration or MIC = 2.14 M). Using gas chromatography coupled to mass spectrometry (GC/MS), eight VOCs were found specifically emitted by CHA0 grown on LBA compared to the bacterium grown on potato dextrose agar (PDA). Among them, two compounds were even more toxic than ammonia against H. abietinum: dimethyl trisulfide had EC50 = 0.02 M and MIC = 0.2 M, and 2-ethylhexanol had EC50 = 0.33 M and MIC = 0.77 M. The fungus growth inhibition was the result of severe cellular and sub-cellular alterations of hyphae occurring as early as 15 min of exposure to VOCs, as evidenced by transmission and scanning electron microscopy observations. Transcriptome reprogramming of H. abietinum induced by CHA0’s VOCs pointed out that detrimental effects occurred on ribosomes and protein synthesis while the cells tried to react by activating defense mechanisms, which required a lot of energy diverted from the growth and development (fitness cost)
Leuconostoc mesenteroides strain MS4-derived bacteriocins: A potent antimicrobial arsenal for controlling Xylella fastidiosa infection
No full textXylella fastidiosa subsp. pauca (Xfp) currently presents a serious threat to agriculture in Europe and in the Mediterranean, following its discovery in several countries. Addressing this bacterial plant disease with traditional agricultural practices and management strategies has proven inadequate, highlighting the urgent need for effective and environmentally safe antibacterial solutions. In this study, we explored the antibacterial activity of the lactic acid bacterium Leuconostoc mesenteroides strain MS4-derived bacteriocins against Xfp, utilizing a combination of in vitro and in planta experiments. In particular, the cell-free precipitate (CFP) derived from strain MS4 culture in MRS broth, suppressed Xfp growth on BCYE agar plate, whereas protease K-treated CFP was inactive, highlighting the presence of antimicrobial compounds of proteinaceous nature. Additionally, fluorescence and transmission electron microscopy analyses showed that the CFP exhibits a bactericidal effect on Xfp cells, characterized by membrane disruption and subsequent cellular damage. The whole-genome sequencing and bioinformatic analysis revealed that MS4 genome consists of a circular chromosome of 1860,891 bp and a circular plasmid of 37,317 bp and most importantly to encompass six bacteriocin-encoding genes, with a peptide size ranging from 45 to 59 amino acids. MALDI-TOF/TOF MS and RPLC-ESI-MS assays performed on cell-free supernatant (CFS) confirmed the secretion of four (out of 6) bacteriocins (denoted MK-45, MR-53, MW-56, and MG-58) by MS4 in MRS broth. In spot assays, these bacteriocins displayed significant lethality against Xfp, with a minimum lethal concentration between 0.2 and 0.4 mg/mL. The application of CFP on Xfp-infected Nicotiana benthamiana plants, implemented both as preventive and curative approach, successfully controlled the infection, resulting in no visible symptoms 40 days post-inoculation. The finding of MS4 as a natural source of various potent bacteriocins against Xfp, coupled with a significant production under low-cost and uncomplicated laboratory conditions, make of MS4 a cost-effective and realistic option for sustainable management of Xf-related diseases
Isolation and partial characterization of a novel cytorhabdovirus from citrus trees showing foliar symptoms in Iran
Full text linkCitrus ringspot is a graft-transmissible disease, and at least two taxonomically distinct viral species are associated with this syndrome: Citrus psorosis virus (CPsV) and Indian citrus ringspot virus (ICRSV). Neither of these two viruses was detected, however, by serological or molecular assays in symptomatic tissues from citrus trees in southern Iran, where the ringspot syndrome is widespread. By contrast, electron microscopy and molecular assays revealed the presence of a rhabdovirus-like virus, which was graft transmitted to several citrus species and mechanically to herbaceous hosts. Virus particles were bacilliform and resembled rhabdovirus nucleocapsids deprived of the lipoprotein envelope. Partial sequences of the viral nucleoprotein and RNA polymerase genes showed a distant genetic relatedness with cytorhabdoviruses. This virus appears to be a novel species, for which the name Iranian citrus ringspot-associated virus (IrCRSaV) is suggested
Survey of Auchenorrhyncha in the Salento peninsula in search of putative vectors of Xylella fastidiosa subsp. pauca CoDiRO strain
Full text linkXylella fastidiosa (Xf) was identified in September 2013 in olive trees affected by the Olive quick decline syndrome (OQDS) in the Salento peninsula (southern Italy) and denoted Xf strain CoDiRO. Xf is comprised of a group of genetically diverse bacteria in the class Gammaproteobacteria that causes severe plant diseases in many crops and ornamentals. The bacterium is acquired and transmit- ted by xylem-sap feeding hemipterans such as sharpshooter leaf- hoppers (Cicadellidae, Cicadellinae), froghoppers and spittlebugs (Aphrophoridae and Cercopidae) and, possibly, cicadas (Cicadidae and Tibicinidae). Due to the rapid spread and devastation associ- ated with OQDS, a survey of candidate vectors of Xf was conducted from September 2013 in the Gallipoli area in accordance to a EFSA list (EFSA, 2013). Four candidate vector species were identified: (i) Aphrophoridae: Philaenus spumarius L. and Neophilaenus camp- estris Fallen; (ii) Cercopidae: Cercopis sanguinolenta Scopoli; (iii) Ci- cadidae: Cicada orni L. Among these, only P. spumarius, the meadow spittlebug, was experimentally proven to be a vector of X. fastidiosa strain CoDiRO. A high percentage of meadow spittlebugs collected from OQDS-affected orchards, from May to September 2014, tested positive for X. fastidiosa by PCR. Transmission to periwinkle plants was successful. Laboratory tests, so far limited to the Philaenus-ex- posed periwinkle seedlings, will be extended to the entire panel of the host plants (olives, grapes, citrus, oleander and Prunus spp.) that were exposed to infectious spittlebugs. Further ongoing experiments include Xf-free spittlebugs that were allowed to feed on infected olives and other hosts plants prior to transferring onto receptor host plants. The results so far obtained have shown that olive is a source of inoculum from which P. spumarius is able to acquire the bacte- rium and transfer it to other olives. These data strongly suggest that the main vector of Xf in the area of it occurrence is P. spumarius. Transmission tests carried out with other xylem sap feeders found in the OQDS area are also discussed
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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