Communication in the Plant Microbiota

The root density of plant microbiota is estimated at 10⁸-10⁹ microbes per gram of soil. It can reach the value of 10¹⁰ microbes on the surface of exuding mature roots (rhizoplane) where biofilms often develop. Its diversity would be greater than 30,000 bacterial species.

Because of this heterogeneity and anthropogenic releases, the plant microbiota also harbors isolates belonging to opportunistic or non-opportunistic human pathogenic species. The collective genome of this community is thus considered as a second genome of the eukaryotic host (notion of holobiont).

This microbiota develops various beneficial, neutral or deleterious relationships with the host plant, which can be exploited for crop protection (biocontrol), environmental (input reduction) and health (food quality and safety) purposes.

Our work concerns the interactions between partners of the rhizosphere, in particular the intercellular communications at the origin of bacterial social behaviors (e.g. population synchronization of virulence, synthesis of biofilms).

More specifically, we study quorum-sensing communications mediated by diffusible or volatile molecular signals, as well as exchanges of effectors carried by type III and VI secretion systems. In this context, the corollary consists in developing innovative biocontrol strategies aimed at jamming these communications by targeting both the messages (e.g. quorum-quenching) and the messengers (e.g. T6SS killing, antibiosis). The strategies developed thus aim to control, or even annihilate, the coordination and virulence of pathogenic agents.

The universality of the molecular and cellular mechanisms studied gives this research a particular interest for fundamental mechanistic research in Microbiology, Biochemistry and Cellular Biology. They find their long-lasting applications, particularly in Agroecology and even human health.

Keywords: Bacterial communications, Rhizosphere, Phytopathology, Biocontrol, Agroecology