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21.
Hanspeter A. Pfirter Florence Marquis Genevieve Defago 《Biocontrol Science and Technology》1999,9(4):555-566
Genetic variation among 38 isolates of Stagonospora sp. and 10 isolates of Septoria sp. from bindweed was studied using (a) restriction fragment length plymorphism (RFLP) analysis of the internal transcribed spacer (ITS) region, and (b) random amplified polymorphic DNA (RAPD) PCR analysis. RFLP analysis revealed three types of fragment patterns among the isolates. A total of 26 distinct groups, based on common fragment patterns, were identified using cluster analysis of the RAPD-PCR data. When the grouping results of the two methods were compared, the fragment pattern types and clusters were generally in agreement. The degree of pathogenicity of six genetically characterized isolates of Stagonospora sp. was assessed on three ecotypes of field bindweed (Convolvulus arvensis). Disease symptoms were observed with all isolates on all ecotypes, but only Stagonospora convolvuli strain LA39, a potential biocontrol agent, showed a high degree of pathogenicity on all ecotypes. A mixture of two Stagonospora sp. enhanced the mean necrotic leaf area on bindweed from 33.9 and 39.0% (when applied alone) to 64.9% applied together at the same final concentration of 5 X 106 spores ml -1 . Molecular methods were used to identify the two pathogens. Both were present on the same plant when applied together, but never found in the same lesion. 相似文献
22.
Evolution of dispersal in spatially and temporally variable environments: The importance of life cycles 下载免费PDF全文
François Massol Florence Débarre 《Evolution; international journal of organic evolution》2015,69(7):1925-1937
Spatiotemporal variability of the environment is bound to affect the evolution of dispersal, and yet model predictions strongly differ on this particular effect. Recent studies on the evolution of local adaptation have shown that the life cycle chosen to model the selective effects of spatiotemporal variability of the environment is a critical factor determining evolutionary outcomes. Here, we investigate the effect of the order of events in the life cycle on the evolution of unconditional dispersal in a spatially heterogeneous, temporally varying landscape. Our results show that the occurrence of intermediate singular strategies and disruptive selection are conditioned by the temporal autocorrelation of the environment and by the life cycle. Life cycles with dispersal of adults versus dispersal of juveniles, local versus global density regulation, give radically different evolutionary outcomes that include selection for total philopatry, evolutionary bistability, selection for intermediate stable states, and evolutionary branching points. Our results highlight the importance of accounting for life‐cycle specifics when predicting the effects of the environment on evolutionarily selected trait values, such as dispersal, as well as the need to check the robustness of model conclusions against modifications of the life cycle. 相似文献
23.
Vronique Roig-Zamboni Sarah Barelier Robert Dixon Nicola F. Galley Amani Ghanem Quoc Phong Nguyen Hloize Cahuzac Bartomiej Salamaga Peter J. Davis Yves Bourne Stphane Mesnage Florence Vincent 《The Journal of biological chemistry》2022,298(5)
The cleavage of septal peptidoglycan at the end of cell division facilitates the separation of the two daughter cells. The hydrolases involved in this process (called autolysins) are potentially lethal enzymes that can cause cell death; their activity, therefore, must be tightly controlled during cell growth. In Enterococcus faecalis, the N-acetylglucosaminidase AtlA plays a predominant role in cell separation. atlA mutants form long cell chains and are significantly less virulent in the zebrafish model of infection. The attenuated virulence of atlA mutants is underpinned by a limited dissemination of bacterial chains in the host organism and a more efficient uptake by phagocytes that clear the infection. AtlA has structural homologs in other important pathogens, such as Listeria monocytogenes and Salmonella typhimurium, and therefore represents an attractive model to design new inhibitors of bacterial pathogenesis. Here, we provide a 1.45 Å crystal structure of the E. faecalis AtlA catalytic domain that reveals a closed conformation of a conserved β-hairpin and a complex network of hydrogen bonds that bring two catalytic residues to the ideal distance for an inverting mechanism. Based on the model of the AtlA–substrate complex, we identify key residues critical for substrate recognition and septum cleavage during bacterial growth. We propose that this work will provide useful information for the rational design of specific inhibitors targeting this enterococcal virulence factor and its orthologs in other pathogens. 相似文献
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Kristyn Echterling-Savage Florence D. DiGennaro Reed L. Keith Miller Sean Savage 《Journal of applied animal welfare science : JAAWS》2013,16(2):181-197
Problem behavior of companion animals poses a threat to caregivers, other targets of problem behavior (e.g., strangers, other nonhuman animals), and those animals engaging in problem behavior. This study examined the effects of an aggression reduction procedure (ARP) on dog problem behavior. After a baseline condition showing caregivers were unsuccessful in reducing dog aggression and the behaviors preceding aggression, caregivers were trained to implement a procedure to address dog problem behavior in relatively simple contexts. Generalization programming then was used to target caregiver plan implementation and dog problem behavior in more complex contexts. The ARP effectively reduced dog aggression for all dogs. A slight reduction and increased variability in dog precursor behavior was observed when the ARP was implemented. In addition, caregivers and experts rated the goals, procedures, and effects as acceptable. Implications of these findings are discussed. 相似文献
29.
Michel Camplo Philippe Faury Anne-Sophie Charvet Florence Lederer Jean-Claude Chermann Jean-Louis Kraus 《Nucleosides, nucleotides & nucleic acids》2013,32(6):631-641
Abstract The synthesis of a new analogue of 2′,3′-dideoxy-3′-thiacytidine 9 covalently linked to an N-formyl methionyl leucyl phenylalanine peptide is described. This new prodrug analogue has been tested on the one hand as activator of human polymorphonuclear leukocytes (an EC50 value of 1.8 10?5 M was determined from dose-response curve for superoxide production) and on the other hand as inhibitor of the syncitium formation caused by HIV-1 in MT4-cells (IC50 = 8.0± 0.8 μM). In so far as this new prodrug possesses these two biological properties, it represents a useful “chemical-head” capable of targeting specific receptors located on leukocytes membranes. 相似文献
30.
Florence Miller Hervé Lécuyer Olivier Join‐Lambert Sandrine Bourdoulous Stefano Marullo Xavier Nassif Mathieu Coureuil 《Cellular microbiology》2013,15(4):512-519
The brain and meningeal spaces are protected from bacterial invasion by the blood–brain barrier, formed by specialized endothelial cells and tight intercellular junctional complexes. However, once in the bloodstream, Neisseria meningitidis crosses this barrier in about 60% of the cases. This highlights the particular efficacy with which N. meningitidis targets the brain vascular cell wall. The first step of central nervous system invasion is the direct interaction between bacteria and endothelial cells. This step is mediated by the type IV pili, which induce a remodelling of the endothelial monolayer, leading to the opening of the intercellular space. In this review, strategies used by the bacteria to survive in the bloodstream, to colonize the brain vasculature and to cross the blood–brain barrier will be discussed. 相似文献