2,589 research outputs found
Manipulation of the symbiont microbiota of insect pests for the development of sustainable control strategies in the agri-food chain
No full textManipulation of symbiotic associations in insect pests represents a promising approach within the framework of Integrated Pest Management (IPM). Indeed, by targeting the bacterial symbionts that play essential roles in the biology and survival of their host, it is possible to develop targeted pest control strategies reducing environmental impact and risks on non-target organisms. In this context, the present doctoral thesis explores the relationship of four insect pests with specific microorganisms, as a target for the development of sustainable control strategies.
The four insect pests are relevant for primary production and for food storage: Halyomorpha halys damages a wide range of crops, including fruit and vegetables, Bactrocera oleae is a major pest of olive trees, and Lobesia botrana targets grapevines, while Periplaneta americana is ubiquitous in many urban and industrial environments and it is responsible for food contamination and hygiene issues in urban and industrial settings. Those pests contribute to important economic losses across agricultural sectors and food storage, as they reduce crop yields, compromise food quality, and increase management costs, resulting in a significant challenge for sustainable food systems.
Three of the above-mentioned insects, namely H. halys, B. oleae, and P. americana are associated with microbial endosymbionts, which are vertically transmitted to the offspring and which occupy specific locations in the respective host. On the contrary, no stable associations for L. botrana have been confirmed.
Taxonomically speaking, the known primary symbionts belong to different species and genera of family Enterobacteriaceae, in H. halys and B. oleae, and Flavobacteriaceae in P. americana. The in vitro uncultivability represents a significant challenge, as it limits both the ability to investigate their biological role for the insect host, and the possibility to screen antimicrobial compounds that could effectively interfere with bacterial viability.
Given the specificities of each association between insect pests and related microbial symbionts, the four case studies were analyzed with different experimental strategies.
The first study insect investigated was Halyomorpha halys (Heteroptera: Pentatomidae), the host of Candidatus Pantoea carbekii. The microbial presence on externally deposed eggs was the basis to develop an innovative pipeline of analyses to screen the effect of low-environmental-risk Plant Protection Products (PPPs). The integration of fast microbiological analyses directly on the egg masses (live/dead staining with fluorescence microscopy) and observations on egg hatching and nymphal viability provided a complete overview of effects of PPPs.
As a proof-of-concept, fungicides and plant biostimulants were tested, with two application modes (spraying and dipping) and results showed that compounds with different use in agriculture could modulate the endosymbiont viability impairing also the insect development. The same compounds were also tested on the parasitoid Trissolcus japonicus, a biocontrol agent for H. halys.
The results demonstrated that they did not affect parasitoid emergence nor their ability to parasitize treated eggs, highlighting the compatibility with symbiotic control.
The second case study involved Bactrocera oleae (Diptera: Tephritidae) and its endosymbiont Candidatus Erwinia dacicola, located mainly in the esophageal bulb in adult. Given the similarity of the endosymbiont to the free-living species E. aphidicola, a novel selective growth medium was developed.
Computational approaches, including phylogenomics, comparative genomics, and metabolic modeling, combined with the use of E. aphidicola as a proxy species, enabled the formulation of a completely new growth medium.
Culturing trials were performed along two seasons and when insects where available. Growth was observed only in primary cultures, which allowed the identification of key nutritional factors necessary for cultivation. However, further optimization is needed to enable successful subculturing.
As a complementary approach, E. aphidicola was employed as a proxy species to investigate the antimicrobial resistance pattern possibly shared with Ca. E. dacicola which could extend ineffective compounds to be used for symbiotic control. The Minimum Inhibitory Concentrations (MICs) were determined for the free-living E. aphidicola and genome-based analyses were performed to determine core genes shared by the two species. Results showed that E. aphidicola, exhibited the most concordant phenotypic resistance/susceptibility profile and is the most similar to the endosymbiont at the genetic level of resistance profiles suggesting that it could be considered a reliable tool to hypothesize antimicrobial effectiveness against Ca. E. dacicola.
A comprehensive literature review was performed on L. botrana (Lepidoptera: Tortricidae). Unlike other pests, it does not appear to host obligate symbionts, and a previously suspected mutualism. All the available information on the microbiota associated with species of Lepidoptera in general and Tortricidae in particular, and possible differences during the developmental stages. Based on current knowledge, microbial agents could be applied in a form of biological control, in a framework of IPM, even though a “standard” symbiotic control is not possible due to the lack of stable symbionts.
The last case study regarded P. americana (Blattodea: Blattidae), a relevant food-related pest, which hosts an obligate endosymbiont of the genus Blattabacterium. Given the availability of 97 genome sequences (more specifically, metagenome-assembled-genomes or MAG) of uncultured Blattabacterium spp., an analysis of metadata revealed that the broad range of cockroaches host species for different lineages of this genus. Further, a genome-based analysis showed that Blattabacterium associated with P. americana represent a distinct genomovar, genomically distinguishable from B. cuenoti, the species usually indicated as the symbiont. Finally, a survey of the current knowledge on the symbiosis was performed to evaluate the potential for developing symbiotic control strategies for this resilient insect in pest management for stored food products.
The integration of microbiological, computational and entomological techniques allowed to pursue applied purpose like the proposal of a novel pipeline of analyses for compound testing and leveraged on the use of genome data to address culturability, investigate susceptibility/resistance to antimicrobial compounds as well as determine the correct identification of endosymbionts.
Overall, the findings of this doctoral project contributed both to the scientific understanding of microbial endosymbiont characteristics and to the development of novel approaches in the light of sustainable pest management, including also the impact on non-target organisms, in line with the principles of IPM systems
A real CKM Matrix ?
No full textThe hypothesis of a real Cabibbo-Kobayashi-Maskawa matrix has been considered and found to be disfavoured by present measurements even when neglecting results from CP violation in neutral kaon decay. The Best Linear Unbiased Estimator has been used as a statistical approach to compute the confidence level. This result agrees with most of the previous literature but contradicts statements reported in a recent paper
Applications of cosmic-ray muons
No full textApplications of cosmic-ray muons have grown in numbers in the last decades. This was possible thanks to the development of detectors and techniques employed in particle and nuclear physics. Indeed the first famous application, the scanning of the Chephren's pyramid, was performed by L. W. Alvarez, that was a great expert in particle detectors and indeed was awarded a Nobel prize for his work on the hydrogen bubble chambers. After a first period in which the applications exploited mainly the absorption of the cosmic-ray muons when crossing a structure under investigation, more recently also the deflection of the muons has been used to design new applications. Nowadays more and more groups around the world are working on this research field. In the present review, after an introduction on cosmic-ray muons, the principles of the interaction of muons with matter will be briefly summarised. This description is important to classify the applications in three main categories: muon radiography, muon tomography and muon metrology. In the following, for each class, an overview of the basic ideas and a detailed description of the technologies will be presented along with a list of past and present applications
HEADACHE AND ENDOCRINE DISORDERS. A CASE REPORT OF HEADACHE DUE TO WITHDRAWAL AND PRIMARY HYPERALDOSTERONISM
No full textHeadache and endocrine desorders. A case report of headache due to estrogens withdrawal and to primary hyperaldosteronism
No full textSugar mimics:an artificial receptor for cholera toxin
No full textThe paper describes the pseudosugar 2 [Galβ1-3GalNAcβ1-4(NeuAcα2- 3)DCCHD], a high affinity binder of cholera toxin (CT). The molecule was designed using molecular modeling techniques to mimic the natural CT membrane receptor, ganglioside GM1. The central residue of GM1, a 3,4-disubstituted galactose unit, was recognized as the ganglioside scaffold element and substituted with a conformationally locked cyclohexanediol (DCCHD). DCCHD was synthesized in enantiopure form using enantioselective Diels Alder methodology and regioselectively α-sialylation at the equatorial position. Glycosylation with a Galβ(1-3)-GalNAc donor completed the synthesis of 2. The solution structure of 2 and its binding ability to CT were found to be analogous to those of the GM1 oligosaccharide.</p
Relaxor ferroeletric behavior in S r1-x P rxTi O3: Cooperation between polar and antiferrodistortive instabilities
No full textChemical doping at the Sr and Ti sites is a feasible way to alter the quantum paraelectric state of SrTiO 3 perovskite. Doping with Pr is known to induce relaxor ferroelectricity at room temperature in the Sr1-xPrxTiO 3 solid solution. The relationship between its dielectric properties and structural phase transition has been debated, but no definitive structural argument has been proposed. Here we present a systematic structural study of Sr1-xPrxTiO 3 (0.020≤x≤0.150). We establish the structural phase diagram using high-resolution x-ray powder diffraction by finding the antiferrodistortive structural phase transitions for all the compositions studied. By using pair distribution function analysis, we show the mismatch between local and long-range structures in terms of increased local order parameters. Finally, we propose a correlation between the local structural order parameters and the emergence of hard polar modes as found by Raman spectroscopy. Our results are quantitatively consistent with recent theoretical calculations showing that the increase of local tetragonality and local octahedral tilting above a critical value in fact underlie the polar instability. This confirms that structural orders involving both polar and antiferrodistortive characters compete and cooperate at different levels, promoting ferroelectricity in Sr1-xPrxTiO 3
The CALorimetric Electron Telescope (CALET) space experiment for the direct measurement of high energy electrons in cosmic rays
No full textThe CALorimetric Electron Telescope (CALET) is a Japanese-led international space mission by JANA (Japanese Aerospace Exploraticai Agency) in Collaboration with the Italian Space Agency (ASI) and NASA. The apparatus was launched to the International Space Station on 19 August 2015. Its main objective is to explore the region above 1 TeV with precise direct measurements of the electron positron and nuclei spectra. The instrument consists of a charge detection device composed of two layers of plastic scintillators, a finely-segmented sampling calorimeter with scintillating fibers (3 radiation lengths) and a homogeneous calorimeter made of PWO scintillating bars (27 radiation lengths). In parallel with the calorimeter another instrument, the CALET Gamma-ray Burst Monitor (CCBM), operates as a gamma-ray burst monitor using two different kinds of scindilators to detect photons from 7 keV to 20 51eV. In this work a brief review of the electron analysis Will be discussed focusing on the electron/proton discrimination power estimated with different Monte Carlo simulations. Some published results about calibration and search for electromagnetic counterparts of the LIG G-V 151226 gravitational wave event will be presented too
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