Littérature scientifique sur le sujet « Commensalismo »

We analyze the global stability of the coexisting equilibria for several models of commensalism, first by devising a procedure to modify several Lyapunov functionals which were introduced earlier for corresponding models of mutualism, further confirming their usefulness. It is seen that commensalism promotes global stability, in connection with higher-order self-limiting terms which prevent unboundedness. We then use the theory of asymptotically autonomous systems to prove global stability results for models of commensalism which are subject to Allee effects, finding that commensalisms of appropriate strength can overcome the influence of strong Allee effects.

Commensalisms, interactions between two species in which one species benefits and the other experiences no net effect, are frequently mentioned in the ecological literature but are surprisingly little studied. Here we review and synthesize our limited understanding of commensalism. We then argue that commensalism is not a single type of interaction; rather, it is a suite of phenomena associated with distinct ecological processes and evolutionary consequences. For each form of commensalism we define, we present evidence for how, where, and why it occurs, including when it is evolutionarily persistent and when it is an occasional outcome of interactions that are usually mutualistic or antagonistic. We argue that commensalism should be of great interest in the study of species interactions due to its location at the center of the continuum between positive and negative outcomes. Finally, we offer a roadmap for future research.

This paper suggests and analyses a model consisting of two commensal populations with Michaelis-Menten type of harvesting for the first population. The first harvested commensal species draws strength from the second hosted species. The overall dynamics are provided to achieve the coexistence, stability and persistence of the equilibrium points for the proposed system. The local bifurcation near the positive equilibrium point is attained. Moreover, numerical simulation using MATLAB is investigated to the impact of the commensalism interaction on the behavior of the planned model. The analysis shows that the role of commensalismpr events the first population from extinction, which could be helpful for the survival of both species.

Candida species are both opportunistic fungal pathogens and common members of the human mycobiome. Over the years, the main focus of the fungal field has been on understanding the pathogenic potential and disease manifestation of these organisms. Therefore, understanding of their commensal lifestyle, interactions with host epithelial barriers, and initial transition into pathogenesis is less developed. In this review, we will describe the current knowledge on the commensal lifestyle of these fungi, how they are able to adhere to and colonize host epithelial surfaces, compete with other members of the microbiota, and interact with the host immune response, as well as their transition into opportunistic pathogens by invading the gastrointestinal epithelium.

In this paper, we propose and analyze a commensalism model with nonmonotonic functional response and density-dependent birth rates. The model can have at most four nonnegative equilibria. By applying the differential inequality theory, we show that each equilibrium can be globally attractive under suitable conditions. However, commensalism can be established only when resources for both species are large enough.

2007/2008
Nel mondo contemporaneo, i territori metropolitani presentano in larga misura fenomeni di instabilità urbana causati soprattutto da flussi migratori sempre crescenti, dovuti principalmente all’apertura delle frontiere e alla recessione economica. Questo fenomeno globale dovrebbe sollecitare la nostra disciplina a ricercare soluzioni abitative a costi ragionevoli e a tempo determinato. Nella realtà europea emerge un sistema-città che, nel suo insieme, non è definibile come entità data, certa, immutabile, sulla quale sovrapporre un nuovo disegno, è invece un sistema aperto in continua trasformazione, in perenne mutazione. Questo scritto parte dal presupposto che i modelli di intervento finora applicati per gestire il fabbisogno abitativo, o anche l’habitat minimo progettato per eventi calamitosi, possano ampliare i loro orizzonti verso nuove emergenze legate alle attuali esigenze sociali ed economiche di una sempre più considerevole porzione della popolazione. Lo spazio urbano è attraversato oggi da perenni flussi – di automobili, di persone, di informazioni – difficilmente gestibili con una pianificazione a lungo termine, ma solo limitatamente alla predisposizione di infrastrutture di collegamento dei sistemi urbani, la disciplina architettonica dovrebbe (potrebbe) assimilare la nozione di mutazione con la messa a punto di manufatti ad assetti variabili in grado di rispondere ad esigenze funzionali transitorie. La trattazione si sviluppa con l’intento di indagare quei fenomeni di modificazioni urbane temporanee che si collegano, non solo all’autogestione del territorio da parte del fruitore che costruisce, per necessità o spontaneamente, la propria casa, nonché di esaminare alcuni progetti teorici, in parte utopici e in parte futuribili degli ultimi cinquant’anni elaborati soprattutto da gruppi di avanguardia. Sono state indagate, pertanto, alcune micro realtà abitative connesse alla necessità di insediamento in contesti metropolitani in cui è difficile ritrovare il concetto di casa inteso come elemento di riconoscibilità geopolitica: fenomeni d’emergenza abitativa incontrollati, inseriti all’interno del tessuto urbano indifferentemente, innesti temporanei che compaiono e scompaiono velocemente, aggredendo qualsiasi porzione di spazio libero, dalle aree industriali dismesse, agli snodi infrastrutturali, ai centri storici fatiscenti. Ai limiti tra l’autocostruzione e la pratica dell’abusivismo, frequentemente, il tipo di rapporto che queste micro realtà instaurano con il tessuto urbano segue le regole parassitarie di vicendevole alleanza tra due insiemi biologici e garantisce la sopravvivenza di entrambi, ma su livelli diversi: quello legale, costituito da piani di sviluppo speculativi o in cui non esistono strumenti urbanistici efficaci e quello illegale, governato dall’esigenza di sopravvivere in condizioni metropolitane avverse. La richiesta di alloggi temporanei permette inoltre di considerare il costruito in maniera differente: scenario dove poter agganciare la casa, dove poter innestare l’habitat minimo in posizioni strategiche, innescando rapporti simbiotici tra l’esistente e l’innesto. Si tratta di fenomeni che, se analizzati criticamente, possono portare a conclusioni inedite. Proprio in Italia, paese nel quale poco si demolisce e molto si conserva, manipolazioni di questo tipo potrebbero rinnovare aree depresse o vaste zone industriali dismesse. Se si considera la residenza come efficace strumento di controllo sociale, i diversi gradi di simbiosi che si possono stabilire tra il costruito e gli innesti potrebbero generare risultati proficui sia sul piano economico ma soprattutto psicosociale degli utenti. L’architettura potrebbe scoprire una nuova espressività, una nuova scrittura, potrebbe nascere un’architettura virale che, come ci suggerisce Franco Purini, sia il risultato di una molteplicità di processi formali di tipo infettivo.
Nella prima parte si analizza una sezione della cultura architettonica europea che, nella seconda metà XX secolo, ha caratterizzato la ricerca disciplinare innescando un forte ripensamento sui mezzi e sulle finalità dell’architettura stessa, promuovendo modelli insediativi rivolti ad una società dotata di un alto grado di mobilità sociale. Fughe in avanti che sembrano sopite, ma dalle quali si possono ancora trarre utili insegnamenti – come dimostrano alcuni dei protagonisti dell’attuale dibattito architettonico globale – e ritrovare spunti di riflessione per gestire la complessità della metropoli contemporanea, concepita come modello dinamicamente e costantemente in evoluzione, in perenne accelerazione. Il pre-testo della ricerca affonda le radici nel saggio di Andrea Branzi Le profezie dell’architettura radicale, apparso nel volume Radicals a cura di Gianni Pettena del 1996. In esso Branzi definisce l’architettura radicale non tanto come «un movimento culturale preciso, piuttosto come un fenomeno energetico, un ‘territorio sperimentale’ che ha investito la cultura del progetto europeo tra gli anni Sessanta e gli anni Settanta». La ricerca tende ad individuare un filo rosso nel vasto dibattito sul tema dell’abitare radical attraverso la rilettura di alcuni frammenti che compongono le testimonianze del periodo, peraltro non ancora debitamente sistematizzate. Sono stati indagati avvenimenti e dibattiti del tempo, soprattutto in quei paesi in cui le lotte sociali hanno, senza alcun dubbio, condizionato le ricerche disciplinari. L’Italia, la Gran Bretagna, l’Austria e la Francia, tra il 1960 e il 1970, sono state considerate realtà rappresentative di condizioni in cui gli scontri ideologici legati all’esplosione della cultura di massa hanno prodotto sperimentazioni originali atte a rispondere alle trasformazioni sociali in atto, mettendo in discussione gli strumenti e le metodologie del progetto urbano e architettonico. I radicals, in ambito accademico prima e in quello professionale poi, hanno prodotto visioni di città future in cui l’uomo può liberamente muoversi in costruzioni dagli assetti variabili in grado di rispondere rapidamente alle richieste funzionali di un’utenza non più certa del proprio futuro ed in costante e continua evoluzione . Tra schizzi frettolosi, disegni ironici, fotomontaggi arditi prodotti nel periodo oggetto di indagine, sono stati selezionati alcuni studi sull’habitat minimo, fughe in avanti che tendevano a produrre oggetti, all’epoca, materialmente irrealizzabili ma divenuti oggi plausibili, in relazione alle opportunità fornite dallo sviluppo tecnologico, sia dal punto di vista costruttivo che funzionale.
Nella seconda parte, sono stati analizzati piccoli manufatti realizzati per aggiunta, per scavo, per manomissione del tessuto urbano contemporaneo, ponendo particolare attenzione a quelli di dimensioni abitative ridotte che, con la loro capacità di collaborare e/o di scontrarsi con pezzi di realtà costruita, si impastano con essa producendo inedite derive urbane. Operazioni di manipolazioni dell’esistente che coinvolgono principalmente due questioni: il limite da porre alla delirante espansione urbana e la riconversione ecologica dello stock edilizio contemporaneo prodotto, in particolar modo in Italia, durante il boom economico degli anni Cinquanta. Presa coscienza dell’impossibilità di operare con strategie edilizie che partano da un grado zero o che necessitino di modificare l’esistente in un ottica anti tabula rasa, sono stati privilegiati alcuni esempi campione che rielaborano e riarticolano il tessuto della città e dell’architettura, con scale d’intervento inattese, verosimilmente microscopiche. Nella contemporaneità si sono individuate due linee di ricerca che poggiano su presupposti simili e si sviluppano declinando scelte tecnologiche high o low tech. Da un lato, l’architettura rubata, fatta di micro inserimenti staminali innestabili sull’esistente, che producono soluzioni abitative legali, e dall’altro l’architettura dei rifiuti, fatta di oggetti di scarto, frutto della sovrabbondanza contemporanea di beni materiali, che vengono utilizzati per la costruzione di soluzioni abitative in territori illegalmente occupati. Entrambi gli approcci si legano a nuove o ritrovate esigenze d’uso dell’ambiente domestico e derivano sovente, dal parassitismo biologico, il concetto di mutazione. L’architettura della manipolazione o dell’innesto, può indicare alcune linee guida grazie alle quali operare in lembi urbani residuali tenendo conto della possibilità di variazione spontanea del costruito. Al di là degli evidenti aspetti di parassitismo connessi alle forme di sopravvivenza tipiche degli homeless, dei campi nomadi, delle conurbazioni improvvisate, delle favelas presenti in larga misura, ormai anche in Europa, ancor più interessante è rintracciare oggi metodologie costruttive parassitarie in tessuti urbani consolidati, legate a situazioni sociali connotate da preoccupanti fenomeni di precarietà economica. A conclusione della seconda parte sono state inserite, quasi a margine della trattazione generale, quindici schede sinottiche descrittive di progetti manifesto, di studi per piccole cellule, di esempi di habitat parassita, costruzioni inedite che, come sopra accennato, risultavano solo pochi lustri addietro carichi di componente utopica, sogni nei cassetti di giovani intellettuali vagheggianti mondi non sempre possibili. Queste microarchitetture risultano tuttavia oggi di grande attualità e addirittura fattibili con le tecnologie presenti sul campo. Ci sono apparsi pertanto come veri e propri riferimenti per altrettanti oggetti architettonici realizzati nella contemporaneità che, quasi provocatoriamente, sono stati accostati ai loro progenitori in questa piccola rassegna al fine di far meglio comprendere e cogliere criticamente il messaggio di un non lontano passato.
Nella terza parte sono documentati alcuni progetti, da me elaborati nel triennio, come strumenti di verifica degli assunti della ricerca: due concorsi internazionali sul tema dell’habitat minimo e gli esiti di un workshop didattico progettuale al quale ho partecipato in veste di tutor presso la Facoltà di Architettura di Trieste.
XXI Ciclo
1976

Le microbiote a un impact majeur sur la physiologie de son hôte, cependant notre compréhension des mécanismes régulant la relation hôte/microbiote reste limitée. Nous utilisons un hôte modèle simple, la Drosophile, afin de répondre à ces questions. Durant mon doctorat, je me suis attaché à une étape particulière du cycle de vie de la Drosophile, sa phase larvaire. Celle-ci constitue sa phase de croissance et est influencée par le contexte nutritionnel. Le microbiote influence également cette étape: l’association avec la bactérie Lactobacillus plantarum tempère les effets de la carence alimentaire en soutenant un taux de croissance élevé et une maturation rapide, en modulant chez l’hôte l’activité de l’hormone Ecdysone et de l’insuline. En retour, L.plantarum bénéficie de l’association, les larvesassurant sa persistance dans la niche (la niche étant le substrat nutritif, les larves et les bactéries associées). Pour caractériser les mécanismes mis en jeu dans ce mutualisme nous avons décrit les réponses transcriptomiques et métaboliques de la larve et avons également étudié les perturbations métaboliques de la niche. Nos résultats mettent en avant l’optimisation de l’extraction des acides aminés du substrat comme facteur clef du mutualisme. L.plantarum active l’expression des protéases intestinales de l’hôte via la voie IMD/NF-κB, et bénéficierait en retour d’une quantité d’acides aminés plus importante assurant sa persistance. Ainsi, nos travaux contribuent à l’effort de compréhension desmécanismes régulant l’interaction hôte/microbiote et pourraient conduire à de nombreuses applications thérapeutiques, notamment dans le cadre de déséquilibres nutritionnels
Symbiotic bacterial populations (also called the “microbiota”) have a dramatic impact on their host’s physiology. However, our understanding of the mechanisms shaping host/microbes mutualism remains limited. We took advantage of Drosophila tractability to characterize the host’s and the microbial factors engaged in mutualism. During my PhD, I focused on the impact of the microbiota during the Drosophila larval phase, which constitutes its juvenile growth period. Drosophila larval phase is influenced by nutrition, but also by symbiotic microbes: specific association with the bacterium Lactobacillus plantarum buffers the deleterious effects of nutrient scarcity on the host’s juvenile growth, by sustaining greater growth rates and hastening maturation. L.plantarum mediate these effects by modulating the activity of the steroid hormone Ecdysone and the Insulin/Insulin-like Signaling pathway in its host. In return, L.plantarum benefits from Drosophila presence, as larvae ensure its long-term persistence in the niche (the niche being the nutritive substrate, the larvae and the bacteria dwelling on it). To characterize the mechanisms engaged in this mutualistic relationship, we described the host’s transcriptomic and metabolic responses to L.plantarum presence and characterized the metabolic perturbations occurring in the niche. Our results put forward the optimization of amino-acids extraction from the nutritive substrate as a cornerstone of mutualism. L.plantarum activates the expression of the host’s digestive proteases via IMD/NF-κB signaling and would benefit in return from an enhanced AA availability, which would help sustaining its long-term persistence. Altogether, our studies contribute to the understanding of the mechanisms regulating host/microbiota interaction and could lead to numerous therapeutic applications, notably aiming at counteracting the deleterious effects of nutritional imbalances

Dans la première partie de notre Thèse, nous avons revu la littérature de l’ensemble des espèces méthanogènes retrouvées dans les différents microbiotes de l’homme. Nous avons également fait un point sur les diverses méthodes utilisées en microbiologie clinique pour rechercher et identifier ces microorganismes. Dans une seconde partie de notre thèse, nous avons montré que le tractus digestif humain est colonisé par M. smithii dès le premier jour de la vie posant ainsi la question des sources potentielles d’acquisition de ce méthanogènes. Nous avons détecté et isolé M. smithii et M. oralis dans le colostrum et dans le lait maternel suggérant ainsi une contamination mère-enfant par allaitement. Concernant les prélèvements vaginaux, M. smithii est détecté dans 97 % des prélèvements collectés chez des patientes ayant une vaginose bactérienne. Par la suite, nous avons rapporté la détection de méthanogènes, M. oralis et M. smithii dans le fluide salivaire d'individus ne souffrant d'aucune maladie bucco-dentaire. Dans la troisième partie de notre thèse, nous avons montré pour la première fois que les méthanogènes font partie du microbiote urinaire dans lequel nous avons trouvé M. smithii avec une prévalence de 9 %. Enfin, nous avons optimisé les méthodes de recherche et d’isolement des méthanogènes. Nous avons développé une méthode chimique de production d’H2. L’expertise acquise et les résultats obtenus au cours de cette Thèse, nous invitent à poursuivre des travaux de recherche en microbiologie clinique des méthanogènes, en questionnant plus particulièrement leurs rôles en physiologie et en pathologie buccodentaire
In the first part of our thesis, we reviewed the literature of all the methanogenic species found in the different microbiota of humans. We also reviewed the various methods used in clinical microbiology to research and identify these microorganisms. In a second part of our thesis, we have shown that the human digestive tract is colonized by M. smithii from the first day of life thus posing the question of potential sources of acquisition of this methanogen. We detected and isolated M. smithii and M. oralis in colostrum and breast milk suggesting mother-to-child contamination by breastfeeding. For vaginal specimens, M. smithii is detected in 97% of the samples collected from patients with bacterial vaginosis. Subsequently, we reported the detection of methanogens, M. oralis and M. smithii in the salivary fluid of individuals with no oral disease. In the third part of our thesis, we have shown for the first time that methanogens are part of the urinary microbiota in which we found M. smithii with a prevalence of 9%. Finally, we have optimized the methods of research and isolation of methanogens. We have developed a chemical method for producing H2. The expertise acquired and the results obtained during this thesis, invite us to continue research work in clinical microbiology of methanogens, questioning more particularly their roles in physiology and oral pathology

Parce qu'ils sont constamment en contact avec toutes sortes de microorganismes présents dans leur environnement, les organismes pluricellulaires ont développé un système immunitaire qui leur permet de détecter leur présence et contrôler leur croissance. Les contacts se produisent naturellement au niveau des surfaces de l'animal qui sont exposés à l'environnement extérieur, comme la peau ou les muqueuses. Il existe au minimum deux types d'interactions : dans le premier cas, la présence de l'autre ne cause aucun problème pour chacun, et peut même éventuellement apporter un bénéfice. Dans le second, l'un des partenaires est aggressif envers l'autre, qui doit répondre à cette situation de stress en essayant de préserver son intégrité pour assurer sa survie. Du côté de l'hôte, cette réponse implique le système immunitaire et a généralement pour but de détruire le microorganisme. En utilisant l'insecte drosophila melanogaster comme organisme hôte modèle, j'ai étudié les interactions hôtes - microbes. Dans le cadre d'un premier projet, je me suis interessé aux cellules circulantes de la drosophiles, les plasmatocytes. Nous savions qu'elles sont capables de manifester certaines activités biologiques (sécrétion de cytokine et de facteurs coagulant, phagocytose), mais leur importance dans la résistance aux infections n'a jamais été évaluée. En générant des drosophiles dépourvues de plasmatocytes, j'ai pu montrer que ces cellules sont requises pour assurer la résistance à certaines infections bactériennes systémiques chez l'adulte, dont Staphylococcus aureus et Salmonella typhimurium, mais pas toutes
Because they are constantly exposed to contact with the various type of microorganisms present in their environment, multicellular organisms have evolved an immune system that allow them to sense their presence and control their growth. Close contact with these microbes naturally occurs in body parts that are exposed to the environment, like external body surfaces and internal mucosa, and at least two diffrerent kind of relations can be described. In the first case both the two parts do not harm the other, eventually allowing the relationship to go for a mutual benefit. In the second case, one part is agressive towards the other and lead it to induce a response to this stressful situation in order to preserve it's integrity and ultimately it's survival. From the host point of view, this response involves the immune system and most frequently aims at the eradication of the microbes. Using the fruitfly drosophila melanogaster as a model for the host side, i was interested in studying host-microbe interactions. A first project i worked on focused on drosophila circulating cells, the plasmatocytes, about which we knew some activities (secretion of cytokines, cloting factors, phagocytosis) but whose functional relevance to resist infection has never been tested. By generating plasmatocytes-depleted flies, I show that these cells are required for the survival of the adult upon some type of systemic bacterial infections, including Staphylococcus aureus and Salmonella typhimurium, but not all

Le commensalisme est une association biologique au sein de laquelle le commensal obtient un avantage, alors que son hôte n'obtient ni avantage, ni désavantage. Ce type d'association est théorisé durant la seconde moitié du dix-neuvième siècle, notamment par Pierre-Joseph Van Beneden (1809-1894). Zoologiste belge, professeur à l'université de Louvain, il propose dans son ouvrage de 1875 intitulé Les commensaux et les parasites dans le règne animal, 264 exemples d'associations qu'il classe parmi le commensalisme. Ses travaux ont un retentissement majeur dans l'univers des zoologistes de son époque. Le concept de commensalisme perdure alors jusqu'au vingt-et-unième siècle et interroge sur les notions d'individualité, d'individuation et d'association. Notre étude porte non seulement sur le développement de ce concept au cours du dix-neuvième siècle, que nous démontrons par de nombreux documents inédits issus des archives de Pierre-Joseph Van Beneden, mais aussi sur la pérennité du concept jusqu'à nos jours. Le commensalisme est interprété comme un " marqueur " de l'émergence de nouvelles sciences du vivant : la microbiologie et l'écologie. Plus qu'un concept scientifique, le commensalisme apparaît alors comme un concept illustrant la complexité du vivant

A handful of rat species are among the most pervasive mammal species across the globe, primarily because of their close relationship with humans. The processes involved in this relationship, commensalism, are described in detail. Two rat species, Rattus rattus and Rattus exulans, are the focus of this thesis and their biology and taxonomy are described and discussed. Their modern distributions are the direct result of some of the earliest and most extensive human migration events in human history. The archaeology of the Pacific and Indian Oceans is described and migration vectors and spheres of interaction are identified. These possible patterns of human migration and exchange networks provide testable hypotheses that can be investigated using the subject rat species as proxies for long distance human movement. Modern and archaeological tooth samples of R. exulans and modern samples of R. rattus are analysed using geometric morphometrics. The results reveal important aspects of human migration and differences between these species' biology. R. exulans was likely to have been transported out of Island Southeast Asia at a very early date. Human colonisation of the Pacific occurred in a series of complex pulses and pauses that are clearly reflected in the R. exulans data. For the first time it is possible to demonstrate, within one dataset, the multiple origins and directions of colonisation across the Pacific. The R. rattus data provides a striking comparison, showing very different results that allude to a different level of modern gene-­‐ flow and therefore a difference in behaviour and biology. The results provide a framework for comparison with future archaeological material. The results presented and hypotheses raised have immediate application to existing archaeological material and areas of interest. Further commensal species should be examined following similar lines of questioning as applied here.

Nous voulions déterminer les facteurs de l'anthropisation impliqués dans le commensalisme de la souris, selon une approche phylogéographique et historique.
La quantification de la variabilité actuelle des morphologies dentaires (analyses de Fourier) du genre Mus en Méditerranée a montré qu'il est possible de discriminer les espèces et sous-espèces du genre à partir du matériel fossile et qu'elle pouvait être un marqueur des flux géniques.
L'application archéozoologique nous a permis d'identifier l'émergence des pratiques de l'économie agricole néolithique (stockage des grains, champs cultivés...) au Proche-Orient comme le facteur déterminant dans l'adaptation de la souris à la niche commensale.
Enfin, nous avons montré que la souris domestique colonisa la Méditerranée occidentale lors de l'intensification conjointe des échanges et de l'urbanisation du premier millénaire av. J.-C., lui permettant de surmonter les barrières écologiques et génétiques qui, auparavant, empêchaient son invasion.

Nous voulions déterminer les facteurs de l'anthropisation impliqués dans le commensalisme de la souris, selon une approche phylogéographique et historique. La quantification de la variabilité actuelle des morphologies dentaires (analyses de Fourier) du genre Mus en Méditerranée a montré qu'il est possible de discriminer les espèces et sous-espèces du genre à partir du matériel fossile et qu'elle pouvait être un marqueur des flux géniques. L'application archéozoologique nous a permis d'identifier l'émergence des pratiques de l'économie agricole néolithique (stockage des grains, champs cultivés. . . ) au Proche-Orient comme le facteur déterminant dans l'adaptation de la souris à la niche commensale. Enfin, nous avons montré que la souris domestique colonisa la Méditerranée occidentale lors de l'intensification conjointe des échanges et de l'urbanisation du premier millénaire av. J. -C. , lui permettant de surmonter les barrières écologiques et génétiques qui, auparavant, empêchaient son invasion
We aimed to determine the factors of the anthropisation involved in the mouse commensalism, using both phylogeographical and historical approaches. The quantification of the variability in the molar shape (Fourier analyses) of Mediterranean mice species showed that it is possible to separate species and sub-species of the genus using dental morphology and that this variability might be a marker of genes flow. Zooarchaeological analyses allowed us to identify the emergence of Neolithic farming practices (seeds storage, cultivated fields. . . ) in the Near East as the determining factor for the adaptation of the mouse to the commensal niche. Finally, we showed that the house mouse colonized the western Mediterranean during the intensification of both exchanges and urbanization in the first millennium BC, allowing it to overcome the ecological and genetic barriers which, previously, prevented its invasion

Ce travail s'integre dans une problematique generale cherchant a determiner quels aspects de l'environnement de la souris domestique peuvent participer a l'etablissement d'une divergence chromosomique (par suite de fixation de fusions robertsoniennes) dans certaines de ses populations. La souris domestique occupe deux types d'habitat exterieur et commensal. Le phenomene robertsonien est correle avec l'habitat commensal. Ici le commensalisme est considere dans ses aspects sociaux resultant des fortes densites et de la reproduction continue dans ce type d'habitat. La sensibilite des individus de differentes populations a un stress psychogenique est mesuree a l'aide d'un indice physiologique: le taux de corticosterone plasmatique. Differents stress sont experimentes: la capture, l'exposition a un environnement nouveau et la rencontre d'un congenere inconnu. La corticosteronemie basale en periode diurne permet d'evaluer la reactivite quotidienne des individus. Ces differents indices permettent de differencier au sein de chaque population etudiee les femelles plus emotives que les males, et parmi les differentes populations de distinguer celles qui proviennent d'un habitat commensal de celles provenant de l'habitat exterieur. En habitat commensal les individus montrent une faible sensibilite vis-a-vis d'un stress psychogenique et une forte reactivite quotidienne, le contraire est observe chez les souris exterieures. Les resultats sont interpretes en terme d'adaptation. Les souris robertsoniennes semblent montrer une strategie mixte qui pourrait etre a l'origine d'un avantage adaptatif. Un nouveau modele sur la mise en place du phenomene est propose

L'habitat naturel du babouin hamadryas (papio hamadryas hamadryas) en Arabie saoudite a été profondément altère par le récent développement socio-économique du pays, et certaines populations de babouins sont devenues dépendantes de sources de nourriture d'origine humaine. Un recensement des populations commensales et des conflits hommes/babouins à travers le royaume a permis de mesurer l'ampleur de ce phénomène et d'identifier les causes de son développement singulièrement rapide. Différentes méthodes de lutte contre le commensalisme du babouin hamadryas ont par ailleurs été évaluées, et des solutions pratiques sont proposées pour la gestion des populations commensales et pour la conservation de l'espèce en Arabie saoudite. Afin de mieux comprendre les mécanismes de l'adaptation du babouin hamadryas au mode de vie commensal, l'étude socio-écologique d'une troupe de plus de 1,500 individus vivant sur le site de la décharge municipale de la ville de Taif été effectuée. Les résultats obtenus ont montré de fortes ressemblances entre la structure et l'organisation sociale de cette troupe et celles de troupes sauvages (société organisée en plusieurs niveaux dont l'unité de base est l'unité familiale, système de fission-fusion de la troupe lors des marches quotidiennes, utilisation d'un dortoir central). Mais d'importantes différences ont également été observées (existence de groupes de males célibataires, altération de l'exclusivité sexuelle au sein des unités familiales, etc. ). Ces disparités semblent pouvoir s'expliquer par une modification des stratégies socio-sexuelles individuelles, aussi bien des males que des femelles, sous l'effet de facteurs environnementaux liés au commensalisme (apport artificiel d'une nourriture riche et abondante et densité de population considérablement accrue). Le babouin hamadryas, considère au sein du genre papio comme le spécialiste des milieux semi-arides, semble donc capable d'une certaine flexibilité comportementale en réponse à des variations à court terme de son environnement écologique et social. Ceci suggère que son système social n'est pas aussi rigidement et irréversiblement spécialise qu'on a pu le croire jusqu'à présent.

Fungal plant pathogens are responsible for extensive annual crop and revenue losses throughout the world. To better understand why fungi cause diseases, we performed gene-disruption mutagenesis on several pathogenic Colletotrichum species and demonstrated that pathogenic isolates can be converted to symbionts (mutualism, commensalism, parasitism) expressing non-pathogenic lifestyles. The objectives of this proposal were to: 1- generate crop-specific mutants by gene disruption that express mutualistic lifestyles, 2- assess the ability of the mutualists to confer disease resistance, drought tolerance, and growth enhancement to host plants, 3- compare fslm1 sequences and their genomic locations in the different species, and 4- document the colonization process of each Colletotrichum species.It was demonstrated that wildtype pathogenic Colletotrichum isolates, can be converted by mutation from expressing a pathogenic lifestyle to symbionts expressing non-pathogenic lifestyles. In the US, mutants of Colletotrichum were isolated by homologous gene disruption using a vector containing a disrupted FSlm1 sequence while in Israel, C. acutatum mutants were selected by restriction enzyme mediated integration (REMI) transformation. One group (US) of non-pathogenic mutants conferred disease protection against pathogenic species of Colletotrichum, Fusarium, and Phytophthora; drought tolerance; and growth enhancement to host plants. These mutants were defined as mutualists and disease resistance correlated to a decrease in the time required for hosts to activate defense systems when exposed to virulent fungi. The second group (Israel) of non-pathogenic mutants did not confer disease resistance and were classified as commensals. In addition, we demonstrated that wildtype pathogenic Colletotrichum species can express non-pathogenic lifestyles, including mutualism, on plants they colonize asymptomatically. The expected long term contribution of this research to agriculture in the US and Israel is threefold. Host-specific mutualists will be utilized in the various crops to confer (1) disease resistance to reduce dependence on chemical fungicides; (2) drought tolerance to reduce water consumption for irrigation; (3) growth enhancement to increase yields.