Interference of quorum sensing in Pseudomonas syringae by bacterial epiphytes that limit iron availability
Article first published online: 7 JUN 2010
© 2010 Society for Applied Microbiology and Blackwell Publishing Ltd
Special Issue: Pseudomonas. Editors: Professors Burkhard Tummler, Victor de Lorenzo, Alain Filloux and Joyce Loper
Volume 12, Issue 6, pages 1762–1774, June 2010
How to Cite
Dulla, G. F. J., Krasileva, K. V. and Lindow, S. E. (2010), Interference of quorum sensing in Pseudomonas syringae by bacterial epiphytes that limit iron availability. Environmental Microbiology, 12: 1762–1774. doi: 10.1111/j.1462-2920.2010.02261.x
- Issue published online: 7 JUN 2010
- Article first published online: 7 JUN 2010
- Received 25 January, 2010; accepted 31 January, 2010.
Leaf surfaces harbour bacterial epiphytes that are capable of influencing the quorum sensing (QS) system, density determination through detection of diffusible signal molecules, of the plant-pathogen Pseudomonas syringae pv. syringae (Pss) which controls expression of extracellular polysaccharide production, motility and other factors contributing to virulence to plants. Approximately 11% of the bacterial epiphytes recovered from a variety of plants produced a diffusible factor capable of inhibiting the QS system of Pss as indicated by suppression of ahlI. Blockage of QS by these interfering strains correlated strongly with their ability to limit iron availability to Pss. A direct relationship between the ability of isogenic Escherichia coli strains to sequester iron via their production of different siderophores and their ability to suppress QS in Pss was also observed. Quorum sensing induction was inversely related to iron availability in culture media supplemented with iron chelators or with FeCl3. Co-inoculation of interfering strains with Pss onto leaves increased the number of resultant disease lesions over twofold compared with that on plants inoculated with Pss alone. Transposon-generated mutants of interfering strains in which QS inhibition was blocked did not increase disease when co-inoculated with Pss. Increased disease incidence was also not observed when a non-motile mutant of Pss was co-inoculated onto plants with QS interfering bacteria suggesting that these strains enhanced the motility of Pss in an iron-dependent manner, leading to an apparent increase in virulence of this pathogen. Considerable cross-talk mediated by iron scavenging apparently occurs on plants, thereby altering the behaviour of bacteria such as Pss that exhibit important QS-dependent traits in this habitat.