Water stress is one of the major environmental factors limiting the crop productivity . Plant stress responses are very complex and drought tolerance may be linked to the presence of specific microorganisms in the rhizosphere. Indeed, some plant growth promoting bacteria (PGPR) strains have been found to improve plant growth under abiotic stresses. Among the many mechanisms by which those PGPR can support plant growth, the emission of volatile organic compounds (VOCs) and their biological impact are still under study. The aim of this work is to evaluate the interaction between the model grass Brachypodium distachyon (Bd21) and two strains of PGPR. The impact of volatile emission on Bd21 growth was studied using an ex-vitro cocultivation system without physical contact between plant and bacteria during 10 days. This peculiar system was developed to assess bacterial VOCs impacts on plants under realistic growth and stress conditions. In parallel, the response of Bd21 seedlings to water deficit induced by polyethylene glycol 6000 (PEG 6000) was studied to establish contrasted growth conditions regarding water availability.