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Cell density-dependent gene contributes to efficient seed colonization by Pseudomonas putida KT2440.
Manuel Espinosa-Urgel1, Juan-Luis Ramos
1Department of Plant Biochemistry and Molecular and Cellular Biology, Estacíon Experimental del Zaidín, CSIC, Granada 18008, Spain. manuel.espinosa@eez.csic.es
Applied and Environmental Microbiology
|September 4, 2004
Summary
The Pseudomonas putida KT2440 ddcA gene is crucial for corn seed colonization. Its expression is regulated by cell density, suggesting a quorum-sensing system involved in bacterial adhesion.
Area of Science:
- Microbiology
- Bacterial Genetics
- Plant-Microbe Interactions
Background:
- The gene ddcA in Pseudomonas putida KT2440 is implicated in initial colonization of corn seeds.
- ddcA encodes a conserved membrane protein with unknown function, found across prokaryotes.
Purpose of the Study:
- To characterize the expression pattern of the ddcA gene.
- To investigate the regulatory mechanisms controlling ddcA expression.
- To explore the role of ddcA in bacterial seed adhesion and colonization.
Main Methods:
- Gene expression analysis under various growth conditions.
- Mutant complementation studies to assess gene function.
- Cell density and conditioned medium experiments to identify regulatory signals.
Main Results:
- ddcA expression is maximal at the onset of the stationary phase.
- Expression is independent of RpoS, nutrient or phosphate starvation, and pH changes.
- ddcA expression is directly dependent on cell density and stimulated by conditioned medium and seed exudates.
- Multicopy expression of ddcA restored seed adhesion in a ddcA mutant.
Conclusions:
- ddcA plays a role in bacterial seed adhesion and colonization.
- Cell density-dependent expression of ddcA suggests a quorum-sensing system in P. putida KT2440.
- This represents the first evidence of quorum sensing in P. putida KT2440, potentially impacting plant colonization.