Bacterial Cross-Talk in the Phyllosphere: Interference of Pseudomonas syringae's Quorum Sensing System

EPA Grant Number: FP916423
Title: Bacterial Cross-Talk in the Phyllosphere: Interference of Pseudomonas syringae's Quorum Sensing System
Investigators: Dulla, Glenn F.J.
Institution: University of California - Berkeley
EPA Project Officer: Hahn, Intaek
Project Period: January 1, 2004 through December 31, 2006
Project Amount: $102,508
RFA: STAR Graduate Fellowships (2004) RFA Text |  Recipients Lists
Research Category: Fellowship - Microbiology , Academic Fellowships , Biology/Life Sciences


The objectives of this research project are to: (1) determine the role of the quorum sensing (QS) system in the epiphytic growth, survival, and pathogenesis of the plant pathogen Pseudomonas syringae pv. syringae (Pss); (2) determine the effects on interactions of Pss with plants caused by other bacteria that interfere with QS in Pss; (3) identify the genetic elements of bacterial isolates responsible for interference of QS; and (4) document interspecific interactions of the QS cross-talk on the leaf surface at small scales.


To address these objectives several approaches will be utilized. QS mutants of Pss have been generated. These mutants currently are being observed for phenotypes, such as motility, exopolysaccharide production, and plant virulence, that would affect the epiphytic growth, survival, and pathogenesis of Pss on bean plants. Expression of required phenotypes for QS and associated traits also will be monitored in culture and on plants using biosensor plasmids harboring green fluorescent protein (GFP) fusions. An extensive transposon mutagenesis screen of bacterial epiphytes able to activate or inhibit Pss QS system will provide information on the process of QS activation or inhibition. Coinoculation studies of such strains with Pss, in vivo and in planta, will reveal effects on QS regulated traits in Pss. Genetically marked strains will be coinoculated onto leaves and visualized with confocal fluorescent microscopy to determine how interference with QS alters colonization patterns. Flow cytometry also will be used to quantify the level of QS activity of Pss recovered from the leaf surface. Ultimately, this research aims to understand the role of QS in plant-microbe interactions and to provide new means of biocontrol of plant pathogenic bacteria that employ QS by altering their behavior on plants.

Supplemental Keywords:

fellowship, quorum sensing, epiphytic growth, plant pathogen, Pseudomonas syringae , plant-microbe interactions, bacterial cross-talk, plant-microbe interations, biocontrol, pathogenic bacteria,, RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Monitoring/Modeling, Environmental Microbiology, Biology, biosensing, microbiology, plant-microbe interactions, bacteria monitoring, plant pathogens

Progress and Final Reports:

  • 2004
  • 2005
  • Final