The genus Burkholderia is an extremely heterogeneous group which includes soil bacteria, plant growth promoting rhizobacteria and human and plant pathogens (Bevivino et al. 1994). Strains of Burkholderia cepacia complex can survive within vacuoles in different isolates of the genus Acanthamoeba (Marolda et al. 1999). In addition, rhizospheric Burkholderia isolates have been found to fix nitrogen (Gillis et al. 1995). In order to understand the role of the intracellular Burkholderia, we have therefore set out to determine whether they have the molecular machinery for the the colonization of eukaryotic cells and for the uptake of mineral nutrients. Since intracellular Burkholderia cannot be grown on a cell-free medium, we took advantage of a genomic library constructed with DNA extracted from Gi. margarita spores (van Buuren et al. 1999): since it was also representative of the bacterial genome, it was used to investigate the prokaryotic genome by screenings with bacterial heterologous probes. Following this approach, a putative phosphate transporter operon (pst) was discovered as well as a gene involved in colonization events by bacterial cells (vacB) (Ruiz Lozano, Bonfante 1999, 2000).
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