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Insects as major threats for human societies

Every year, pests and infectious diseases induced by pathogenic bacteria, viruses, and eukaryotic microorganisms on humans, animals and plants cause more than 12 million human victims (source WHO) and production losses that reach up to 40% worldwide with important concomitant economic losses. The situation is even worsening as geographical distribution of pests and infectious diseases expands in response to climate change and global trade. Arthropods, and notably insects, play a major role in this global picture, either acting as pests or disease vectors. One challenge to the current and future human wellbeing thus concerns the control of these organisms. However, current methods are not efficient enough and mostly rely on unspecific heavy chemical use that deeply impacts the environment while resistance repeatedly arises, urging for the development of alternative specific strategies to fight these threats. Use and management of biodiversity are promising avenues but remain in their infancy or raise safety and sustainability questions. Basic as well as applied research programs are crucially needed to develop innovative solutions to control pests and infectious diseases and reduce the pesticide use in agronomy and health programs.

The emergence of the holobiony concept

Meanwhile, biology is undergoing a paradigm shift. The immense effort invested in the study of the human microbiome has revealed that pathogens are only a subset of the microbial communities hosted by animals: individuals must be considered as holobionts, integrating the entire community of interacting organisms that make them up in a complex symbiotic consortium. Most traits of higher organisms must be considered as extended phenotypes: development, immunity, digestion, reproduction are affected by these microbial interactions. A holistic view of individuals and pathosystems integrating environmental sciences with health and diseases is now required. This paradigm shift has led to new research fields such as “disease ecology” or “agroecology”, where the interaction between a host and a pathogen is replaced in its community and environmental context. Current knowledge demonstrates that the utilization of microorganisms or their products is a promising underexploited direction in order to sustain plant yield or to fight pests and infectious diseases. Managing agroecosystems and controlling pests and diseases thus require the study of interactions between multiple partners (hosts, vectors, pathogens, symbionts) and to decipher the mechanisms underlying these interactions from the gene to the ecosystem.

Insects and their intimate interactions with microorganisms

Insects are the animal group where symbiosis has been the best studied. Many insects host obligatory vertically transmitted primary endosymbionts (P-symbionts), which enable them to exploit unbalanced diets such as blood (e.g. tsetse flies, bedbugs) or phloem sap (e.g. aphids, whiteflies) by providing essential amino acids and various co-factors. Co-evolution over more than hundred millions of years between P-symbionts and hosts has led to highly integrated developmental, physiological and metabolic interactions. Insects are also frequently infected by other heritable facultative secondary symbionts (S-symbionts). S-symbionts can either manipulate the reproduction of their insect hosts or provide benefits comprising exploitation of particular food sources and resistance to different stresses, notably infection by pathogens. Insects also harbor microbiota whose transmission depends more on the environment, notably in their gut, and which participates to digestion and protection against pathogens. These microorganisms are emerging as potential targets for developing control methods of insect pests (e.g. Insect Incompatible Technics) and vectors (e.g. limitation of vector competence using Wolbachia).

MICRO-BE-HAVE : Micro-be-have, understanding and manipulating host-microbes interactions

Spectacular examples of parasite/pathogen manipulations and recent discoveries on commensals and mutualistic symbionts indicate that host-microorganism interactions may widely affect the behavior of the host17–22. These observations have far reaching implications, questioning the “free will” of individuals, the adaptive value of behaviors for the different partners of the interaction, and the impact of symbionts in processes as important as reproductive isolation and speciation or the epidemiology of infectious diseases. Reciprocally, how insects use microbial cues to adapt their behavior is also an emerging field23 that can dramatically change the way we think about the environment and on the way microbiota are transmitted (e.g. do individuals choose their breeding site in order to maximize the chance that their progeny encounters specific microbes?).

By gathering five internationally recognized teams of the IDEXLyon in the fields of insect-microbes interactions, behavioral ecology and engineering sciences, Micro-be-have ambitions to bring new insights on the impact of microorganisms on host behavior that will shed light on the ecological and evolutionary implications of host-microbes interactions in animal species. Micro-be-have will also pave the way to identify specific ecology-driven strategies to control insects. Indeed, while actual control methods mostly target canonical functions (e.g. nervous system, insect gut…), harnessing insect-microbes interactions will allow identifying specific microorganisms or microbe-derived molecules to control insect populations through disruption of the symbiotic relationships and manipulation of insect behavior (e.g. mass-trapping, repellents or sexual confusion).

Microbehave organise le Cycle "Qui sommes-je ? Qui suis-nous ?" dans le cadre de L'Université Ouverte

Nous ne vivons pas isolés. Au contraire, nous respirons grâce à des bactéries logées dans nos cellules, digérons grâce à notre microbiote, et serions peut-être plus sujets à des accidents automobiles en cas d’infection par le toxoplasme ! Ce cycle de 4 conférences nous amènera à revisiter notre relation au monde microbien et notre propre individualité, entre conflit et coopération. Rendez-vous à l'amphithéâtre de l'ENSSIB entre 17 et 19h.

Agenda

9 janvier 2020
Harmonie et jeux de dupe dans les systèmes symbiotiques
Julien Varaldi, maître de conférence, Université Lyon 1

23 janvier 2020
Jouons collectif ! La coopération, un moteur de l’évolution
Natacha Kremer, chargée de recherche CNRS, Université Lyon 1

13 février 2020
Les conflits intérieurs à la lumière de l’évolution
Sylvain Charlat, chargé de recherche CNRS, Université Lyon 1

12 mars 2020
Moi et mon microbiote : l’histoire d’un individu écosystème
Fabrice Vavre, Directeur de recherche CNRS, Université Lyon 1