Conservation of the response regulator gene gacA in Pseudomonas species

Autor: Jos M. Raaijmakers, Mark Mazzola, J. T. De Souza
Rok vydání: 2003
Předmět:
Zdroj: Environmental Microbiology. 5:1328-1340
ISSN: 1462-2920
1462-2912
DOI: 10.1111/j.1462-2920.2003.00438.x
Popis: Summary The response regulator gene gacA influences the pro- duction of several secondary metabolites in both pathogenic and beneficial Pseudomonas spp. In this study, we developed primers and a probe for the gacA gene of Pseudomonas species and sequenced a 425 bp fragment of gacA from ten Pseudomonas strains isolated from different plant-associated envi- ronments. Polymerase chain reaction analysis and Southern hybridization showed that gacA is highly conserved within the genus Pseudomonas : multiple strains of different Pseudomonas species all responded positively to the probe, whereas no response was obtained from 18 other strains repre- senting 14 species that belong to eight different genera of Gram-negative bacteria other than Pseudomonas . Furthermore, from a total of approxi- mately 550 indigenous bacterial isolates obtained from the rhizosphere of wheat, all isolates that hybrid- ized with the gacA probe were classified as Pseudomonas spp. by group-specific primers. Iso- lates that did not respond with the gacA probe and primers were identified as bacterial genera other than Pseudomonas , including Stenotrophomonas , Cry- seomonas and Comamonas spp. These results indi- cate that gacA can be used as a complementary genetic marker for detection of Pseudomonas spp. in environmental samples. Phylogenetic relationships inferred from the newly sequenced gacA fragments and the sequences of gacA homologues present in the databases, showed six distinct clusters that correspond to the following bacterial families: Pseudomonaceae, Enterobacteriaceae, Alteromona- daceae, Vibrionaceae, Burkholderia and Xanthomo- nas. Within the Pseudomonadaceae and Enterobacteriaceae, polymorphisms within gacA and its homologues allowed identification of six and five subclusters respectively. Comparison of the gacA gene and GacA protein-based trees with the tree inferred from 16S rDNA sequences yielded a similar overall clustering. These results suggest that gacA and its homologues may provide complementary markers for phylogenetic studies of Pseudomonas spp. and Gram-negative bacteria other than Pseudomonas .
Databáze: OpenAIRE
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