François Leulier

Background

In the animal kingdom, juvenile growth occurs during the post-natal stage prior to sexual maturation. This period encompasses the most profound physiological changes in the life of an organism. These changes are governed by the complex interaction between the animal’s genotype and its nutritional environment. In humans, 155 million children worldwide are currently chronically undernourished, a condition defined as a prolonged low intake of key nutrients (such as protein). It leads to severe stunting (i.e., slowed linear growth) and long-term neurological, immunological, metabolic and reproductive deficits.
Recent studies, including our own, establish that microbial communities colonizing body surfaces (i.e., microbiota), particularly the activities and constituents of the gut microbiota, can alter the growth trajectory of an animal. In fact, malnourished children carry an “immature” gut microbiota. This “immaturity” cannot be remedied by classical re-nutrition strategies. Moreover, using various animal models, it has been shown that selected strains of gut microbiota members can buffer the deleterious impact of undernutrition on juvenile growth dynamics.
Despite our recent progress, the molecular mechanisms behind such a host benefit mediated by the gut microbiota remain poorly understood. This is partly because the gut microbiota is a complex ecosystem comprising up to hundreds of microbial species in mammals, mainly bacteria. They build high-level nutritional, metabolic and multiplex signaling networks with each other and with their host such that these interactions directly influence host physiology.
Our research

In this context, we aim to decipher how commensal bacteria shape the response of juveniles to their nutritional environment and how juveniles in such a nutritional environment influence the ecology and physiology of their bacterial partners. Therefore, we study microbial ecology and physiology as well as animal development and physiology.
To probe the mechanisms involved in an unbiased manner, we use gnotobiology (rearing animals in strictly controlled microbial environments) coupled with genetics, functional genomics, imaging and biochemical approaches in bacteria (using mainly the model commensal bacteria: Lactobacillus plantarum and Acetobacter spp.) and in Drosophila (Drosophila melanogaster).
We also use microbial interventions (using Lactobacillus plantarum) on conventional mice (Mus musculus) to study the influence of the microbial environment on growth retardation in mammals. Furthermore, we capitalize on a new gnotobiotic mouse model hosting a minimal microbiota composed of 15 bacterial strains representing the most dominant bacterial families found in conventional laboratory mice. Using this model, we study how a controlled microbiota influences the development and physiology of its host during growth under sub-optimal nutritional conditions and we study how the nutritional state influences the ecological dynamics of the members of this microbiota.

Finally, we are developing collaborations with research and development companies to transfer our basic research results into products designed to improve the health and well-being of animals or humans.