Description: Background and aims   Plant-bacterial interactions in the rhizosphere are important in mediating soil nutrient transformations. Plants supply carbon-rich substrates to rhizobacteria as root exudates and bacteria mobilise soil-bound phosphate for plant nutrition. This study aimed to probe the specificity of the plant effect on bacterial gene expression in P-starved rhizosphere conditions. Methods   DNA microarrays were employed to study gene expression in the rhizosphere of Lolium perenne grown under high and low phosphate regimes (330 μM vs. 3–6 μM phosphate). Root exudation under these regimes was also quantified. Phosphate-regulated gene expression of a panel of 22 genes was compared in rhizosphere, planktonic culture and during biofilm growth on an artificial root. Results   Plant growth and root exudation were affected by P-availability. P-limited conditions induced increased expression of bacterial genes of an aromatic degradation pathway ( catA ), heavy metal sensing ( PA2523 ), and membrane proteins ( glpM , crcB ), while genes involved in cell motility and amino acid uptake/ metabolism were downregulated. A crcB mutant was impaired in rhizosphere survival under low phosphate conditions, though glpM and catA mutants were not affected. Several of the genes studied were induced by phosphate limitation in all three lifestyles studied. Conclusions   Our results show the importance of the plant-microbe interaction in controlling the bacterial transcriptional response in a phosphate-limited rhizosphere. Content Type Journal Article Category Regular Article Pages 1-20 DOI 10.1007/s11104-011-1060-z Authors Agnieszka Zyśko, Faculty of Life Sciences, University of Manchester, Oxford Rd, Manchester, M13 9PT UK Hervé Sanguin, Faculty of Life Sciences, University of Manchester, Oxford Rd, Manchester, M13 9PT UK Andrew Hayes, Faculty of Life Sciences, University of Manchester, Oxford Rd, Manchester, M13 9PT UK Leanne Wardleworth, Faculty of Life Sciences, University of Manchester, Oxford Rd, Manchester, M13 9PT UK Leo A. H. Zeef, Faculty of Life Sciences, University of Manchester, Oxford Rd, Manchester, M13 9PT UK Allan Sim, The James Hutton Institute, Craigiebuckler, Aberdeen, AB15 8QH Scotland, UK Eric Paterson, The James Hutton Institute, Craigiebuckler, Aberdeen, AB15 8QH Scotland, UK Brajesh K. Singh, The James Hutton Institute, Craigiebuckler, Aberdeen, AB15 8QH Scotland, UK Michael A. Kertesz, Faculty of Life Sciences, University of Manchester, Oxford Rd, Manchester, M13 9PT UK Journal Plant and Soil Online ISSN 1573-5036 Print ISSN 0032-079X