Добірка наукової літератури з теми "Gamme d’hôte"

Background: Bacteriophages offer one of the most promising solutions to the challenges of antimicrobial resistance in bacteria. The aim of this study is to investigate bacteriophages as a source of new antimicrobial therapy. Methodology: Waste water samples were randomly collected from 8 different locations in the city of Lomé for bacteriophage isolation. The phages were isolated using multi-resistant clinical isolates (Escherichia coli 1642 and Staphylococcus aureus 0868) as hosts by means of a spot test. The host range of the phages was determined also by a spot test using 8 other clinical bacterial isolates including two reference strains (E. coli ATCC 25922 and S. aureus ATCC 29213). The virulence of the phages and their effects on bacterial growth were assessed by in vitro experiments using E. coli 1642 BBec phage suspension. Results: Isolation of phages by the spot test was positive only with the host E. coli 1642. A reduced host range was observed with the other bacteria. The BBec phage suspension showed a titer of 1.6 x 107 PFU/ml. Virulence studies revealed a latency time of less than 10 minutes, a degree of absorption of 87% and a burst size of 63 PFU/cell. The effect of BBec phage suspension on E. coli 1642 showed an almost total reduction in the population of E. coli 1642 after 4 hours. Conclusion: This study provided scientific data showing the antibacterial effect of a phage suspension (BBec) on a multi-resistant clinical isolate of E. coli 1642. This phage could therefore be explored as a candidate for the development of new antibacterial therapies. Contexte : Face aux problèmes de multirésistance des bactéries aux agents antimicrobiens, les bactériophages représentent l’une des solutions les plus prometteuses. L’objectif de ce travail est d’étudier les bactériophages en tant que source de nouvelles thérapies antimicrobiennes . Méthodologie : Des échantillons d'eaux usées ont été collectés de manière aléatoire dans 8 endroits différents de la ville de Lomé pour l'isolement des bactériophages. Les phages ont été isolés en utilisant comme hôtes, des isolats cliniques ( Escherichia coli 1642 et Staphylococcus aureus 0868 ) multirésistants par le biais d’un test ponctuel. La gamme d’hôte des phages a également été déterminée par un test ponctuel utilisant 8 autres isolats dont deux souches de référence ( E. coli ATCC 25922 et S. aureus 29213)29213). L’évaluation de la virulence des phages et leurs effets sur la croissance des bactéries ont été réalisés à travers des expérimentations in vitro avec une suspension de phages d’ E. coli désignée BB ec . Résultats : L’isolement des phages par le test ponctuel s’est révélé positif seulement avec l’hôte E. coli 1642. Une gamme d’hôte réduite a été observée avec les autres bactéries. La suspension de phage BBec a présenté un titre de 1,6 x 107 UFP/ml. L’étude de sa virulence a révélé un temps de latence inférieur à 10 minutes, un degré d’absorption de 87% et une taille de rafale de 63 UFP/Cellule. L’effet de la suspension phagique BBec sur l’isolat E. coli 1642 a montré une réduction quasi totale de la population de l’isolat E. coli 1642 au bout de 4 h. Conclusion : Cette étude a permis de fournir des données scientifiques qui montrent l’effet antibactérien d’une suspension de phage (BBec) sur un isolat clinique multirésistant E. coli 1642. Ce ph age pourrait donc être exploré comme candidat au développement de nouvelles thérapies antibactériennes.

Introduction Cookbooks are an exceptional written record of what is largely an oral tradition. They have been described as “magician’s hats” due to their ability to reveal much more than they seem to contain (Wheaton, “Finding”). The first book printed in Germany was the Guttenberg Bible in 1456 but, by 1490, printing was introduced into almost every European country (Tierney). The spread of literacy between 1500 and 1800, and the rise in silent reading, helped to create a new private sphere into which the individual could retreat, seeking refuge from the community (Chartier). This new technology had its effects in the world of cookery as in so many spheres of culture (Mennell, All Manners). Trubek notes that cookbooks are the texts most often used by culinary historians, since they usually contain all the requisite materials for analysing a cuisine: ingredients, method, technique, and presentation. Printed cookbooks, beginning in the early modern period, provide culinary historians with sources of evidence of the culinary past. Historians have argued that social differences can be expressed by the way and type of food we consume. Cookbooks are now widely accepted as valid socio-cultural and historic documents (Folch, Sherman), and indeed the link between literacy levels and the protestant tradition has been expressed through the study of Danish cookbooks (Gold). From Apicius, Taillevent, La Varenne, and Menon to Bradley, Smith, Raffald, Acton, and Beeton, how can both manuscript and printed cookbooks be analysed as historic documents? What is the difference between a manuscript and a printed cookbook? Barbara Ketchum Wheaton, who has been studying cookbooks for over half a century and is honorary curator of the culinary collection in Harvard’s Schlesinger Library, has developed a methodology to read historic cookbooks using a structured approach. For a number of years she has been giving seminars to scholars from multidisciplinary fields on how to read historic cookbooks. This paper draws on the author’s experiences attending Wheaton’s seminar in Harvard, and on supervising the use of this methodology at both Masters and Doctoral level (Cashman; Mac Con Iomaire, and Cashman). Manuscripts versus Printed Cookbooks A fundamental difference exists between manuscript and printed cookbooks in their relationship with the public and private domain. Manuscript cookbooks are by their very essence intimate, relatively unedited and written with an eye to private circulation. Culinary manuscripts follow the diurnal and annual tasks of the household. They contain recipes for cures and restoratives, recipes for cleansing products for the house and the body, as well as the expected recipes for cooking and preserving all manners of food. Whether manuscript or printed cookbook, the recipes contained within often act as a reminder of how laborious the production of food could be in the pre-industrialised world (White). Printed cookbooks draw oxygen from the very fact of being public. They assume a “literate population with sufficient discretionary income to invest in texts that commodify knowledge” (Folch). This process of commoditisation brings knowledge from the private to the public sphere. There exists a subset of cookbooks that straddle this divide, for example, Mrs. Rundell’s A New System of Domestic Cookery (1806), which brought to the public domain her distillation of a lifetime of domestic experience. Originally intended for her daughters alone, Rundell’s book was reprinted regularly during the nineteenth century with the last edition printed in 1893, when Mrs. Beeton had been enormously popular for over thirty years (Mac Con Iomaire, and Cashman). Barbara Ketchum Wheaton’s Structured Approach Cookbooks can be rewarding, surprising and illuminating when read carefully with due effort in understanding them as cultural artefacts. However, Wheaton notes that: “One may read a single old cookbook and find it immensely entertaining. One may read two and begin to find intriguing similarities and differences. When the third cookbook is read, one’s mind begins to blur, and one begins to sense the need for some sort of method in approaching these documents” (“Finding”). Following decades of studying cookbooks from both sides of the Atlantic and writing a seminal text on the French at table from 1300-1789 (Wheaton, Savouring the Past), this combined experience negotiating cookbooks as historical documents was codified, and a structured approach gradually articulated and shared within a week long seminar format. In studying any cookbook, regardless of era or country of origin, the text is broken down into five different groupings, to wit: ingredients; equipment or facilities; the meal; the book as a whole; and, finally, the worldview. A particular strength of Wheaton’s seminars is the multidisciplinary nature of the approaches of students who attend, which throws the study of cookbooks open to wide ranging techniques. Students with a purely scientific training unearth interesting patterns by developing databases of the frequency of ingredients or techniques, and cross referencing them with other books from similar or different timelines or geographical regions. Patterns are displayed in graphs or charts. Linguists offer their own unique lens to study cookbooks, whereas anthropologists and historians ask what these objects can tell us about how our ancestors lived and drew meaning from life. This process is continuously refined, and each grouping is discussed below. Ingredients The geographic origins of the ingredients are of interest, as is the seasonality and the cost of the foodstuffs within the scope of each cookbook, as well as the sensory quality both separately and combined within different recipes. In the medieval period, the use of spices and large joints of butchers meat and game were symbols of wealth and status. However, when the discovery of sea routes to the New World and to the Far East made spices more available and affordable to the middle classes, the upper classes spurned them. Evidence from culinary manuscripts in Georgian Ireland, for example, suggests that galangal was more easily available in Dublin during the eighteenth century than in the mid-twentieth century. A new aesthetic, articulated by La Varenne in his Le Cuisinier Francois (1651), heralded that food should taste of itself, and so exotic ingredients such as cinnamon, nutmeg, and ginger were replaced by the local bouquet garni, and stocks and sauces became the foundations of French haute cuisine (Mac Con Iomaire). Some combinations of flavours and ingredients were based on humoral physiology, a long held belief system based on the writings of Hippocrates and Galen, now discredited by modern scientific understanding. The four humors are blood, yellow bile, black bile, and phlegm. It was believed that each of these humors would wax and wane in the body, depending on diet and activity. Galen (131-201 AD) believed that warm food produced yellow bile and that cold food produced phlegm. It is difficult to fathom some combinations of ingredients or the manner of service without comprehending the contemporary context within they were consumeSome ingredients found in Roman cookbooks, such as “garum” or “silphium” are no longer available. It is suggested that the nearest substitute for garum also known as “liquamen”—a fermented fish sauce—would be Naam Plaa, or Thai fish sauce (Grainger). Ingredients such as tea and white bread, moved from the prerogative of the wealthy over time to become the staple of the urban poor. These ingredients, therefore, symbolise radically differing contexts during the seventeenth century than in the early twentieth century. Indeed, there are other ingredients such as hominy (dried maize kernel treated with alkali) or grahams (crackers made from graham flour) found in American cookbooks that require translation to the unacquainted non-American reader. There has been a growing number of food encyclopaedias published in recent years that assist scholars in identifying such commodities (Smith, Katz, Davidson). The Cook’s Workplace, Techniques, and Equipment It is important to be aware of the type of kitchen equipment used, the management of heat and cold within the kitchen, and also the gradual spread of the industrial revolution into the domestic sphere. Visits to historic castles such as Hampton Court Palace where nowadays archaeologists re-enact life below stairs in Tudor times give a glimpse as to how difficult and labour intensive food production was. Meat was spit-roasted in front of huge fires by spit boys. Forcemeats and purees were manually pulped using mortar and pestles. Various technological developments including spit-dogs, and mechanised pulleys, replaced the spit boys, the most up to date being the mechanised rotisserie. The technological advancements of two hundred years can be seen in the Royal Pavilion in Brighton where Marie-Antoinin Carême worked for the Prince Regent in 1816 (Brighton Pavilion), but despite the gleaming copper pans and high ceilings for ventilation, the work was still back breaking. Carême died aged forty-nine, “burnt out by the flame of his genius and the fumes of his ovens” (Ackerman 90). Mennell points out that his fame outlived him, resting on his books: Le Pâtissier Royal Parisien (1815); Le Pâtissier Pittoresque (1815); Le Maître d’Hôtel Français (1822); Le Cuisinier Parisien (1828); and, finally, L’Art de la Cuisine Française au Dix-Neuvième Siècle (1833–5), which was finished posthumously by his student Pluméry (All Manners). Mennell suggests that these books embody the first paradigm of professional French cuisine (in Kuhn’s terminology), pointing out that “no previous work had so comprehensively codified the field nor established its dominance as a point of reference for the whole profession in the way that Carême did” (All Manners 149). The most dramatic technological changes came after the industrial revolution. Although there were built up ovens available in bakeries and in large Norman households, the period of general acceptance of new cooking equipment that enclosed fire (such as the Aga stove) is from c.1860 to 1910, with gas ovens following in c.1910 to the 1920s) and Electricity from c.1930. New food processing techniques dates are as follows: canning (1860s), cooling and freezing (1880s), freeze drying (1950s), and motorised delivery vans with cooking (1920s–1950s) (den Hartog). It must also be noted that the supply of fresh food, and fish particularly, radically improved following the birth, and expansion of, the railways. To understand the context of the cookbook, one needs to be aware of the limits of the technology available to the users of those cookbooks. For many lower to middle class families during the twentieth century, the first cookbook they would possess came with their gas or electrical oven. Meals One can follow cooked dishes from the kitchen to the eating place, observing food presentation, carving, sequencing, and serving of the meal and table etiquette. Meal times and structure changed over time. During the Middle Ages, people usually ate two meals a day: a substantial dinner around noon and a light supper in the evening (Adamson). Some of the most important factors to consider are the manner in which meals were served: either à la française or à la russe. One of the main changes that occurred during the nineteenth century was the slow but gradual transfer from service à la française to service à la russe. From medieval times to the middle of the nineteenth century the structure of a formal meal was not by “courses”—as the term is now understood—but by “services”. Each service could comprise of a choice of dishes—both sweet and savoury—from which each guest could select what appealed to him or her most (Davidson). The philosophy behind this form of service was the forementioned humoral physiology— where each diner chose food based on the four humours of blood, yellow bile, black bile, or phlegm. Also known as le grand couvert, the à la française method made it impossible for the diners to eat anything that was beyond arm’s length (Blake, and Crewe). Smooth service, however, was the key to an effective à la russe dinner since servants controlled the flow of food (Eatwell). The taste and temperature of food took centre stage with the à la russe dinner as each course came in sequence. Many historic cookbooks offer table plans illustrating the suggested arrangement of dishes on a table for the à la française style of service. Many of these dishes might be re-used in later meals, and some dishes such as hashes and rissoles often utilised left over components of previous meals. There is a whole genre of cookbooks informing the middle class cooks how to be frugal and also how to emulate haute cuisine using cheaper or ersatz ingredients. The number dining and the manner in which they dined also changed dramatically over time. From medieval to Tudor times, there might be hundreds dining in large banqueting halls. By the Elizabethan age, a small intimate room where master and family dined alone replaced the old dining hall where master, servants, guests, and travellers had previously dined together (Spencer). Dining tables remained portable until the 1780s when tables with removable leaves were devised. By this time, the bread trencher had been replaced by one made of wood, or plate of pewter or precious metal in wealthier houses. Hosts began providing knives and spoons for their guests by the seventeenth century, with forks also appearing but not fully accepted until the eighteenth century (Mason). These silver utensils were usually marked with the owner’s initials to prevent their theft (Flandrin). Cookbooks as Objects and the World of Publishing A thorough examination of the manuscript or printed cookbook can reveal their physical qualities, including indications of post-publication history, the recipes and other matter in them, as well as the language, organization, and other individual qualities. What can the quality of the paper tell us about the book? Is there a frontispiece? Is the book dedicated to an employer or a patron? Does the author note previous employment history in the introduction? In his Court Cookery, Robert Smith, for example, not only mentions a number of his previous employers, but also outlines that he was eight years working with Patrick Lamb in the Court of King William, before revealing that several dishes published in Lamb’s Royal Cookery (1710) “were never made or practis’d (sic) by him and others are extreme defective and imperfect and made up of dishes unknown to him; and several of them more calculated at the purses than the Gôut of the guests”. Both Lamb and Smith worked for the English monarchy, nobility, and gentry, but produced French cuisine. Not all Britons were enamoured with France, however, with, for example Hannah Glasse asserting “if gentlemen will have French cooks, they must pay for French tricks” (4), and “So much is the blind folly of this age, that they would rather be imposed on by a French Booby, than give encouragement to an good English cook” (ctd. in Trubek 60). Spencer contextualises Glasse’s culinary Francophobia, explaining that whilst she was writing the book, the Jacobite army were only a few days march from London, threatening to cut short the Hanoverian lineage. However, Lehmann points out that whilst Glasse was overtly hostile to French cuisine, she simultaneously plagiarised its receipts. Based on this trickling down of French influences, Mennell argues that “there is really no such thing as a pure-bred English cookery book” (All Manners 98), but that within the assimilation and simplification, a recognisable English style was discernable. Mennell also asserts that Glasse and her fellow women writers had an enormous role in the social history of cooking despite their lack of technical originality (“Plagiarism”). It is also important to consider the place of cookbooks within the history of publishing. Albala provides an overview of the immense outpouring of dietary literature from the printing presses from the 1470s. He divides the Renaissance into three periods: Period I Courtly Dietaries (1470–1530)—targeted at the courtiers with advice to those attending banquets with many courses and lots of wine; Period II The Galenic Revival (1530–1570)—with a deeper appreciation, and sometimes adulation, of Galen, and when scholarship took centre stage over practical use. Finally Period III The Breakdown of Orthodoxy (1570–1650)—when, due to the ambiguities and disagreements within and between authoritative texts, authors were freer to pick the ideas that best suited their own. Nutrition guides were consistent bestsellers, and ranged from small handbooks written in the vernacular for lay audiences, to massive Latin tomes intended for practicing physicians. Albala adds that “anyone with an interest in food appears to have felt qualified to pen his own nutritional guide” (1). Would we have heard about Mrs. Beeton if her husband had not been a publisher? How could a twenty-five year old amass such a wealth of experience in household management? What role has plagiarism played in the history of cookbooks? It is interesting to note that a well worn copy of her book (Beeton) was found in the studio of Francis Bacon and it is suggested that he drew inspiration for a number of his paintings from the colour plates of animal carcasses and butcher’s meat (Dawson). Analysing the post-publication usage of cookbooks is valuable to see the most popular recipes, the annotations left by the owner(s) or user(s), and also if any letters, handwritten recipes, or newspaper clippings are stored within the leaves of the cookbook. The Reader, the Cook, the Eater The physical and inner lives and needs and skills of the individuals who used cookbooks and who ate their meals merit consideration. Books by their nature imply literacy. Who is the book’s audience? Is it the cook or is it the lady of the house who will dictate instructions to the cook? Numeracy and measurement is also important. Where clocks or pocket watches were not widely available, authors such as seventeenth century recipe writer Sir Kenelm Digby would time his cooking by the recitation of the Lord’s Prayer. Literacy amongst protestant women to enable them to read the Bible, also enabled them to read cookbooks (Gold). How did the reader or eater’s religion affect the food practices? Were there fast days? Were there substitute foods for fast days? What about special occasions? Do historic cookbooks only tell us about the food of the middle and upper classes? It is widely accepted today that certain cookbook authors appeal to confident cooks, while others appeal to competent cooks, and others still to more cautious cooks (Bilton). This has always been the case, as has the differentiation between the cookbook aimed at the professional cook rather than the amateur. Historically, male cookbook authors such as Patrick Lamb (1650–1709) and Robert Smith targeted the professional cook market and the nobility and gentry, whereas female authors such as Eliza Acton (1799–1859) and Isabella Beeton (1836–1865) often targeted the middle class market that aspired to emulate their superiors’ fashions in food and dining. How about Tavern or Restaurant cooks? When did they start to put pen to paper, and did what they wrote reflect the food they produced in public eateries? Conclusions This paper has offered an overview of Barbara Ketchum Wheaton’s methodology for reading historic cookbooks using a structured approach. It has highlighted some of the questions scholars and researchers might ask when faced with an old cookbook, regardless of era or geographical location. By systematically examining the book under the headings of ingredients; the cook’s workplace, techniques and equipment; the meals; cookbooks as objects and the world of publishing; and reader, cook and eater, the scholar can perform magic and extract much more from the cookbook than seems to be there on first appearance. References Ackerman, Roy. The Chef's Apprentice. London: Headline, 1988. Adamson, Melitta Weiss. Food in Medieval Times. Westport, Connecticut: Greenwood P, 2004. Albala, Ken. Eating Right in the Renaissance. Ed. Darra Goldstein. Berkeley: U of California P, 2002. Beeton, Isabella. Beeton's Book of Household Management. London: S. Beeton, 1861. Bilton, Samantha. “The Influence of Cookbooks on Domestic Cooks, 1900-2010.” Petit Propos Culinaires 94 (2011): 30–7. Blake, Anthony, and Quentin Crewe. Great Chefs of France. London: Mitchell Beazley/ Artists House, 1978. Brighton Pavilion. 12 Jun. 2013 ‹http://www.guardian.co.uk/artanddesign/interactive/2011/sep/09/brighton-pavilion-360-interactive-panoramic›. Cashman, Dorothy. “An Exploratory Study of Irish Cookbooks.” Unpublished Master's Thesis. M.Sc. Dublin: Dublin Institute of Technology, 2009. Chartier, Roger. “The Practical Impact of Writing.” Trans. Arthur Goldhammer. A History of Private Lives: Volume III: Passions of the Renaissance. Ed. Roger Chartier. Cambridge, Massachusetts: Belknap P of Harvard U, 1989. 111-59. Davidson, Alan. The Oxford Companion to Food. New York: Oxford U P, 1999. Dawson, Barbara. “Francis Bacon and the Art of Food.” The Irish Times 6 April 2013. den Hartog, Adel P. “Technological Innovations and Eating out as a Mass Phenomenon in Europe: A Preamble.” Eating out in Europe: Picnics, Gourmet Dining and Snacks since the Late Eighteenth Century. Eds. Mark Jacobs and Peter Scholliers. Oxford: Berg, 2003. 263–80. Eatwell, Ann. “Á La Française to À La Russe, 1680-1930.” Elegant Eating: Four Hundred Years of Dining in Style. Eds. Philippa Glanville and Hilary Young. London: V&A, 2002. 48–52. Flandrin, Jean-Louis. “Distinction through Taste.” Trans. Arthur Goldhammer. A History of Private Lives: Volume III : Passions of the Renaissance. Ed. Roger Chartier. Cambridge, Massachusetts: Belknap P of Harvard U, 1989. 265–307. Folch, Christine. “Fine Dining: Race in Pre-revolution Cuban Cookbooks.” Latin American Research Review 43.2 (2008): 205–23. Glasse, Hannah. The Art of Cookery Made Plain and Easy; Which Far Exceeds Anything of the Kind Ever Published. 4th Ed. London: The Author, 1745. Gold, Carol. Danish Cookbooks: Domesticity and National Identity, 1616-1901. Seattle: U of Washington P, 2007. Grainger, Sally. Cooking Apicius: Roman Recipes for Today. Totnes, Devon: Prospect, 2006. Hampton Court Palace. “The Tudor Kitchens.” 12 Jun 2013 ‹http://www.hrp.org.uk/HamptonCourtPalace/stories/thetudorkitchens› Katz, Solomon H. Ed. Encyclopedia of Food and Culture (3 Vols). New York: Charles Scribner’s Sons, 2003. Kuhn, T. S. The Structure of Scientific Revolutions. Chicago: U of Chicago P, 1962. Lamb, Patrick. Royal Cookery:Or. The Complete Court-Cook. London: Abel Roper, 1710. Lehmann, Gilly. “English Cookery Books in the 18th Century.” The Oxford Companion to Food. Ed. Alan Davidson. Oxford: Oxford U P, 1999. 277–9. Mac Con Iomaire, Máirtín. “The Changing Geography and Fortunes of Dublin’s Haute Cuisine Restaurants 1958–2008.” Food, Culture & Society 14.4 (2011): 525–45. Mac Con Iomaire, Máirtín, and Dorothy Cashman. “Irish Culinary Manuscripts and Printed Cookbooks: A Discussion.” Petit Propos Culinaires 94 (2011): 81–101. Mason, Laura. Food Culture in Great Britain. Ed. Ken Albala. Westport CT.: Greenwood P, 2004. Mennell, Stephen. All Manners of Food. 2nd ed. Chicago: U of Illinois P, 1996. ---. “Plagiarism and Originality: Diffusionism in the Study of the History of Cookery.” Petits Propos Culinaires 68 (2001): 29–38. Sherman, Sandra. “‘The Whole Art and Mystery of Cooking’: What Cookbooks Taught Readers in the Eighteenth Century.” Eighteenth Century Life 28.1 (2004): 115–35. Smith, Andrew F. Ed. The Oxford Companion to American Food and Drink. New York: Oxford U P, 2007. Spencer, Colin. British Food: An Extraordinary Thousand Years of History. London: Grub Street, 2004. Tierney, Mark. Europe and the World 1300-1763. Dublin: Gill and Macmillan, 1970. Trubek, Amy B. Haute Cuisine: How the French Invented the Culinary Profession. Philadelphia: U of Pennsylvania P, 2000. Wheaton, Barbara. “Finding Real Life in Cookbooks: The Adventures of a Culinary Historian”. 2006. Humanities Research Group Working Paper. 9 Sep. 2009 ‹http://www.phaenex.uwindsor.ca/ojs/leddy/index.php/HRG/article/view/22/27›. Wheaton, Barbara Ketcham. Savouring the Past: The French Kitchen and Table from 1300-1789. London: Chatto & Windus, 1983. White, Eileen, ed. The English Cookery Book: Historical Essays. Proceedings of the 16th Leeds Symposium on Food History 2001. Devon: Prospect, 2001.

Les invasions biologiques sont un des facteurs majeurs de perte de la biodiversité. Face à cette menace, plusieurs approches sont utilisées pour contrôler l’expansion des populations d’espèces invasives. La lutte biologique par introduction s’appuie sur la sélection et l’introduction des ennemis naturels spécialistes de l’espèce invasive, appelés agents de lutte biologique, depuis l’aire d’origine vers l’aire d’invasion pour limiter les populations invasives sous un seuil de nuisibilité écologiquement et économiquement acceptable. Ces travaux de thèse se place dans un contexte de lutte biologique par introduction contre le laiteron maraîcher, Sonchus oleraceus (Asteraceae) en Australie. Dans une visée appliquée de gestion de S. oleraceus, nous avons alors adopté une démarche multidisciplinaire pour adresser plusieurs étapes critiques inhérentes au programme de lutte biologique, concernant 1) l’identification de la cible, 2) la compréhension du processus d’invasion et 3) l’anticipation des risques associés aux lâchers des agents via l’étude des réseaux écologiques. L’identification correcte de la cible étant un prérequis pour la recherche des agents de lutte, nous avons défini un caractère diagnostic fiable et pratique à utiliser lors des prospections, à savoir l’ornementation des akènes. Ensuite, nous avons évalué si l’évolution rapide des traits chez S. oleraceus était un mécanisme qui pouvait avoir contribué au succès d’invasion. Nous avons montré que les populations invasives étaient plus performantes que les natives, et que le compromis qui existe entre l’allocation des ressources à la croissance et la reproduction avait évolué, conduisant les populations invasives à investir davantage dans les fonctions de croissance pour un investissement équivalent aux populations natives dans les fonctions de reproduction. Ces résultats ouvrent la voie à d’autres études utiles pour déterminer les conséquences de ces changements pour les futures populations d’agents de lutte. De plus, nous avons abordé de façon préliminaire le rôle du relâchement de la pression d’herbivorie dans le succès d’invasion. Par des inventaires réalisés en Europe et en Australie, nous avons mis en avant un déficit d’ennemis naturels spécialistes dans l’aire d’introduction. Les introductions délibérées d’agents de lutte ne sont cependant pas anodines et un des challenges en lutte biologique réside dans la capacité à anticiper les risques pour la communauté indigène de l’aire d’introduction. Dans le dernier axe de cette thèse, nous avons exploré l’intérêt de l’analyse des réseaux d’interactions écologiques pour aider à la sélection d’agents de lutte. Pour cela une approche solide et transposable combinant technologies moléculaires et données d’observations a été développée pour reconstruire avec fiabilité et une résolution élevée les interactions trophiques entre plantes, herbivores et ennemis naturels. L’analyse de réseau, nous a permis d’identifier 37 espèces utilisant S. oleraceus en aire native et d’apporter des précisions sur la gamme d’hôte écologique de ces herbivores conduisant à 1) cibler ou exclure certains agents de lutte candidats et 2) questionner l’existence de complexes d’espèces lié à la plante hôte, nécessitant confirmation. Par ailleurs, nous avons révélé l’utilisation de ces herbivores par une large gamme d’ennemis naturels, ce qui présente des implications pour l’évaluation des risques indirects. En somme, cette thèse a participé à renforcer les connaissances quant aux processus d’invasion impliqués dans la colonisation du laiteron maraîcher en Australie, justifiant en partie la stratégie de lutte adoptée, et a montré le potentiel de l’analyse des réseaux écologiques pour complémenter les démarches classiques de sélection d’agents présentant un minium de risque
Biological invasions are one of the main driver of biodiversity loss. Several strategies are employed to tackle the expansion of invasive species populations. Among them, introduction biological control is based on selection and release of specialist natural enemies, called biological control agents, from native range to introduced range to decrease the invasive population densities below an ecological and economical acceptable threshold. This PhD thesis is part of a biological control program targeting the common sow thistle, Sonchus oleraceus (Asteracae), an invasive species in Australia. We employed a multidisciplinary approach to address several critical steps of the program, directed towards applied management perspectives, regarding 1) the identification of the target plant, 2) the understanding of the invasion process, and 3) the prediction of risks associated to biocontrol agents release through ecological networks analysis. The accurate identification of the target plant is a prerequisite for the survey of biocontrol agent candidates. As a first step, we thus defined a reliable and convenient diagnostic character to be used in the field, which is the achene ornamentation. Then, we assessed whether rapid evolution could be one of the process that could have contributed to S. oleraceus invasion success. We showed that introduced plants outperformed native ones, and detected a significant shift in the relationship (trade-off) between growth and reproduction, introduced populations tended to invest more in growth that native ones for an equivalent investment into reproductive functions. More investigations would be necessary to determine whether those changes would affect future biocontrol agents. Post-introduction evolution seemed however moderated, and preliminary results obtained through filed surveys realised in Europe and Australia tended to indicate that enemy release had also probably benefited S. oleraceus in Australia. However, the deliberated introduction of biocontrol agents poses risks to the recipient community, and their anticipation is an ongoing challenge in introduction biological control. In the last part of this thesis, we explore the interest of ecological network analysis in supporting biological control selection. Therefore, a powerful and transferable approach based on the combination of molecular tools and observational data have been developed to reconstruct with high levels of taxonomic resolution and interaction recovering, trophic links between plants, herbivores and natural enemies. Network analyses, allowed to determine 37 species using S. oleraceus as food plant in the native range. We were able to detail their field host range, 1) leading to the selection and exclusion of candidate biocontrol agents, and 2) raising the question of potential cryptic host races, that needs to be confirmed. We revealed a wide range of natural enemy species using S. oleraceus herbivores, which is of particular interest for indirect risk assessment. Ecological analysis proved to be complementary to classical specificity tests and has a great potential to support biocontrol agent selection. In conclusion, this PhD thesis strengthened our knowledge on invasion processes involved in the colonisation of the common sow thistle in Australia, partly justifying the control strategy used, and demonstrated the potential offered by ecological network analysis in supporting the selection of minimal-risk agents

Les parasitoïdes sont des insectes dont le cycle de vie se divise en (i) un stade adulte libre durant lequel la femelle dépose des œufs dans, sur ou à proximité des hôtes et (ii) des stades immatures parasites durant lesquels les larves se développent en consommant leur hôte. Ils sont impliqués dans la régulation de la population de leur(s) hôte(s) et sont largement utilisés en lutte biologique pour réduire les dégâts causés par des ravageurs de cultures dans les agroécosystèmes. L’intensité de cette régulation dépend notamment de la gamme d’hôtes du parasitoïde c.à.d. le nombre d’espèces hôtes différentes dans lesquels il est capable de compléter son développement. La gamme d’hôtes théorique d’un parasitoïde a été largement étudiée et est déterminée par sa capacité à localiser, reconnaître et parasiter son hôte (gamme d'hôtes comportemental) et/ou sa capacité à utiliser les ressources de l’hôte et à contourner ses défenses immunitaires (gamme d'hôtes physiologiques). Cependant, les caractéristiques biotiques et abiotiques environnementales, pouvant potentiellement impacter les traits comportementaux et physiologiques des parasitoïdes et finalement la gamme d’hôtes théorique de ces derniers, ont été très peu étudié. C’est dans ce contexte que j’ai développé ma thèse avec pour but principal d’étudier l’impact de différents facteurs écologiques sur la gamme d’hôtes des parasitoïdes. Pour cela, j’ai choisi comme modèle d’étude les parasitoïdes de pucerons, largement utilisés en lutte biologique, et j’ai étudié le rôle (1) des goulots d’étranglement génétique intervenant lors de l’introduction de petites populations de parasitoïdes dans de nouveaux environnements (par exemple, en lutte biologique classique), (2) de la phylogénie des hôtes et des plantes hôtes, (3) des effets bottom-up du stress hydrique chez les plantes hôtes des pucerons, (4) de la relation entre (i) la qualité des pucerons en tant qu’hôte pour la larve de parasitoïde et (ii) la qualité du puceron en tant que source de nourriture (miellat) pour l’adulte et (5) des interactions indirectes induites par la présence d’hôtes alternatifs sub-optimaux, sur la gamme d’hôte théorique des parasitoïdes. La phylogénie des hôtes et des plantes hôtes ont un effet direct sur la gamme d’hôtes des parasitoïdes tandis que les goulots d’étranglement génétique, les effets bottom-up de la plante, la nutrition des parasitoïdes adultes et les interactions indirectes semblent impacter seulement indirectement la gamme d’hôtes des parasitoïdes de pucerons via une modulation de la fitness et/ou taux de parasitisme. Chaque environnement étant différent, l’'étude de l'impact des facteurs écologiques sur la gamme d'hôtes des parasitoïdes est déterminante ; ce travail de thèse a permis de mieux comprendre certains mécanismes impliqués dans le fonctionnement des communautés de parasitoïdes dans les écosystèmes, ainsi que dans l’optimisation possible de programmes de lutte biologique
Parasitoids are insects whose adult females deposit eggs in, on or near hosts and immatures stages develop by host consumption. They are involved in host population regulation and are largely used in biological control to reduce the damages caused by pests in agroecosystems. Their ability to control pest populations mainly depends on their host range i.e., the number of host species enabling offspring production. The parasitoid host range has been largely studied and may depend on its ability to localize, select and sting their hosts (behavioral host range) and/or its ability to consume and circumvent the hosts physiological defenses (physiological host range). However, each ecosystem has his own biotic and abiotic characteristics that can modulate both behavioral and physiological traits of parasitoids but they implication in the host range modulation have rarely been tested. In this context, the objective of my thesis was to evaluate the impact of different ecological factors on parasitoid host ranges. More specifically, I studied the impact of (i) the genetic bottleneck due to the introduction of small parasitoid population in a new area (through classical biological control notably), (ii) the host and host plant phylogenies, (iii) the bottom-up effects of drought stress, (iv) the relationship between the quality of the host and its ability to produce food for the parasitoid and (v) the parasitoid-mediated indirect interactions between unsuitable and suitable hosts, on the aphid parasitoid host range (high implication in biological control). We demonstrated that the aphids and host plant phylogenies are strongly involved in shaping the ecological host range of parasitoids whereas the other factors tested may only modulate the parasitoid fitness and parasitism rate; which may, finally, indirectly modulate the parasitoid host range. Studied the impact of ecological factors on parasitoid host range seems determinant; this thesis enables to better understand some mechanisms involved in parasitoid community functioning and to potentially optimize biological control programs

Le contrôle biologique (C. -B. - l'utilisation d'ennemis naturels pour lutter contre les ravageurs) est durable, écologique et rentable pour contrer la résistance des ravageurs en augmentant l'utilisation des pesticides. Les parasitoïdes des pucerons sont des ennemis naturels communs des pucerons, les principaux ravageurs mondiaux dans l'agriculture. L'étude de la spécificité de l'hôte parasitoïde contribue à (1) comprendre les mécanismes écologiques et évolutifs de l'écosystème et (2) évaluer l'efficacité des agents de lutte biologique et les risques écologiques pour les espèces non ciblées. Cette étude porte sur la spécificité de l'hôte fondamental des parasitoïdes sur les niveaux individuels, en matière de besoins en ressources et dans le contexte des interactions multi trophiques sous stress abiotique environnemental, c'est-à-dire la limitation de l'eau. Aphidius ervi (Hymenoptera: Braconidés: Aphidiinae) a été choisi; ce parasitoïde puceron est largement utilisé comme modèle écologique et comme agent de lutte biologique commercial (BCA). D'une part, l'indice de spécificité de l'hôte A. ervi a été mesuré sur une large gamme d'espèces de pucerons. D'autre part, les impacts indirects de la limitation de l'eau ont été étudiés sur la spécificité de l'hôte du parasitoïde. En outre, les modifications induites par le stress hydrique dans la plante et les traits de vie des pucerons ont été mesurés. A. ervi s'est avéré être une espèce intermédiaire spécialisée qui a attaqué toutes les espèces de pucerons à des taux élevés, mais n'a pas pu se développer correctement sur toutes les espèces. Les quelques espèces qui se développaient bien étaient phylogénétiquement proches et appartenaient à la tribu des Macrosiphini. En outre, une corrélation positive de préférence - performance a été trouvée. Sous stress hydrique, la préférence et la performance des parasitoïdes ont été affectées, causant la perte de la corrélation. La limitation de l'eau a modifié négativement la qualité nutritionnelle de la plante, ce qui a entraîné une faible performance des pucerons sur les plantes hôtes. Ceci à son tour a diminué la convenance des hôtes pucerons pour le parasitoïde. Les effets de la limitation de l'eau n'étaient pas similaires pour toutes les combinaisons plantes-pucerons et dépendaient de plusieurs facteurs, à savoir les mécanismes végétaux adaptés au stress et la spécialisation de l'hôte des pucerons et des parasitoïdes
Biological control (BC - the use of natural enemies to control pests) are sustainable, environmentally friendly and cost-effective methods to counteract pest resistance by increasing pesticide use. Aphid parasitoids are common natural enemies of aphids, the major worldwide pests in agriculture. The study of parasitoid host specificity contributes to (1) understanding ecological and evolutionary mechanisms driving the ecosystem and (2) evaluating the efficiency of biocontrol agents and the ecological risks for non-target species. This study focuses on the parasitoids fundamental host specificity on individual levels, in terms of resource requirements and in the context of multi-trophic interactions under environmental abiotic stress, i.e.water limitation. Aphidius ervi (Hymenoptera: Braconidae: Aphidiinae) was chosen; this aphid parasitoid is used widely as an ecological model and commercial biological control agent (BCA). On the one hand, A. ervi host specificity index was measured on a broad range of aphid species. On the other hand, the indirect impacts of water limitation were investigated on the host specificity of the parasitoid. Furthermore, water stress-induced modifications in the plant and the aphid life-history traits were measured. A. ervi was shown to be an intermediate specialist species who attacked all aphid species at high rates but was unable to develop well on all of them. The few that developed well were phylogenetically close and belong to the Macrosiphini tribe. Interestingly, a positive correlation preference – performance was found. Under water stress, both preference and performance of parasitoids were affected causing loss of the correlation. Water limitation negatively altered the plant nutritional quality resulting in low aphid performance on host plants. This in turn decreased the suitability of aphid hosts for the parasitoid. The impacts of water limitation were not similar across all plant-aphid combinations and depended on several factors, namely stress-adapted plant mechanisms and the host specialization of both aphids and parasitoids