Towards the understanding of microbial dialogues within forest soil ecosystems: study of the metabolic exchanges between Streptomyces and Pseudomonas

PI: Bertrand Aigle (UMR 1128 Dynamique des génomes et adaptation microbienne)

Co-applicants: Pierre Leblond and Justine Galet (Dynamic), Pascale Frey-Klett and Aurélie Deveau (IAM)

Collaboration: Pieter C. Dorrestein, Skaggs School of Pharmacy and Pharmaceutical Sciences,University of California, San Diego (UCSD)

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Context— Microbial communities play important roles in forest soil ecosystems such as nutrient turnover or delivery to plants. In their ecological niches, microbes do not live as independent individuals. They communicate and manipulate theirenvironment and neighboring microbial populations in a process known as metabolicexchange. In environment such as rhizosphere, some microorganisms also establish exchanges with plants. These exchanges are key processes in the structuration of microbial communities, their resilience in response to external perturbations and plant development and health. Nevertheless, little is known about the chemicals and molecular actors involved in these dialogues.

Objectives— We aim to study the metabolic exchanges occurring between our model couple of soil bacteria, Pseudomonas fluorescens BBc6R8 and Streptomyces ambofaciens ATCC23877, and to identify the chemicals acting as communication signals between these species. The second objective is to characterize at the molecular level the actors involved in the transduction of the signalsand the metabolic pathways responding to these signals.

Approaches— To get insight into the microbial dialogue, we will analyse the interactions by Imaging Mass Spectrometrythat allows the spatial and temporal metabolic profiling of live microbialcolonies. The genome sequences being available for both partners, we will couple this approach to global and targeted genome expression analyses of each bacterium to get insight into the transduction pathways of the signals and into the targeted metabolic pathways in the interspecies dialogues.

Expected results and impacts— Deciphering the dialogues between soil microorganisms may help in the future to understand the processes taking place at the interfaces microbes/trees, even soil/microbes/trees and the impact of the microbial communities on the microbes interacting directly on plants and their development such as myccorhizal fungi but also pathogenic microorganisms. The acquired knowledge is expected to be helpful in the future for practices in ecological engineering that aim to optimize the forest soil functioning.