Recent studies have shown that pH plays a major role in the biogeography of micro-organisms. However, the mechanisms that enable specific taxa to establish in low pH environments, while others are excluded have not yet been investigated. In this project, we address this question using Burkholderia as a model genus. The genus Burkholderia (β-Proteobacteria) comprises over 60 species that are characterized by a very versatile metabolism and broad ecological amplitude. Burkholderia sp. are typical soil and rhizosphere inhabitants and engage in a variety of interactions (both mutualistic and parasitic) with other organisms (plants, fungi, animals, humans). We have accumulated evidence that Burkholderia sp. are among those populations that become dominant in acidic soils and we want to investigate the underlying mechanisms responsible for this dominance. The goals of this project are i) to evaluate the role of acid tolerance in the biogeography of the genus Burkholderia, ii) to assess the species-specificity of the acid tolerance and iii) to investigate the mechanisms leading to acid tolerance. This project will lead to a better understanding of the biogeography of the Burkholderia genus and provide valuable information for a broader audience, e.g. for Burkholderia species of agronomical or clinical relevance.