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Mutation in cyaA in Enterobacter cloacae decreases cucumber root colonization.
Daniel P Roberts1, Laurie F McKenna, Xiaojia Hu
1Sustainable Agricultural Systems Laboratory, USDA-Agricultural Research Service, Bldg. 001, Rm. 140, 10300 Baltimore Avenue, Beltsville, MD 20705-2350, USA. robertsd@ba.ars.usda.gov
Archives of Microbiology
|October 7, 2006
Summary
Enterobacter cloacae M59, a mutant deficient in adenylate cyclase (cyaA), showed reduced root colonization in cucumbers. Supplementing with cyclic AMP (cAMP) restored its growth and colonization abilities.
Area of Science:
- Microbiology
- Plant Pathology
- Biotechnology
Background:
- Enterobacter cloacae strains show potential for biological control of Pythium damping-off.
- Understanding bacterial root colonization is crucial for developing effective biocontrol agents.
Purpose of the Study:
- To investigate the role of adenylate cyclase (cyaA) in the root colonization of cucumber by Enterobacter cloacae.
- To characterize the cyaA mutant M59 and its response to cyclic AMP (cAMP).
Main Methods:
- Generated a mini-Tn5 Km transposon mutant (M59) of Enterobacter cloacae 501R3.
- Assessed bacterial populations on cucumber roots, growth, chemotaxis, and acid resistance.
- Performed molecular characterization to identify the insertion site of the transposon.
- Evaluated the effect of exogenous cAMP on mutant M59's growth, chemotaxis, and colonization.
Main Results:
- The cyaA mutant M59 exhibited significantly lower populations on cucumber roots compared to the wild type.
- Strain M59 showed impaired growth and chemotaxis on cucumber root exudates.
- Adenylate cyclase deficiency resulted in drastically reduced intracellular cAMP levels.
- Exogenous cAMP supplementation restored M59's growth, chemotaxis, and enhanced cucumber seedling colonization.
Conclusions:
- The cyaA gene plays a significant role in the colonization of cucumber roots by Enterobacter cloacae.
- Adenylate cyclase activity and cAMP signaling are essential for bacterial root colonization and biocontrol efficacy.
