Adaptation of <i>Pseudomonas fluorescens</i> to the plant rhizosphere

Saprophytic Pseudomonas are common root‐colonizing bacteria that can improve plant health. Efficient exploitation of these bacteria in agriculture requires knowledge of traits that enhance ecological performance in the rhizosphere. Here, I describe the development and application of a promoter‐trapping technology (IVET) that enables the isolation of Pseudomonas fluorescens genes that show elevated levels of expression in the rhizosphere. Using IVET, 20 P. fluorescens genes were identified that are induced during rhizosphere colonization, and their patterns of expression were analysed in laboratory media and in the rhizosphere. Fourteen genes showed significant homology to sequences in GenBank that are involved in nutrient acquisition, stress response, or secretion; six showed no homology. Seven of the rhizosphere‐induced ( rhi ) genes have homology to known non‐ Pseudomonas genes. One of the rhi genes ( hr