|DE Souza, J - WAGENINGEN UNIVERSITY|
|Raaijmakers, J - WAGENINGEN UNIVERSITY|
Submitted to: Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 1, 2003
Publication Date: December 1, 2003
Citation: DE SOUZA, J.T., MAZZOLA, M., RAAIJMAKERS, J.M. CONSERVATION OF THE RESPONSE REGULATOR GENE GACA IN PSEUDOMONAS SPECIES. ENVIRONMENTAL MICROBIOLOGY. 5:1328-1340. 2003. Interpretive Summary: GacA is a response regulator protein which is part of a system that regulates several aspects of bacterial metabolism. The corresponding gene, gacaA, is commonly found among bacteria belonging to the family Pseudomonadaceae. These bacteria have several known important capabilities including the control of soilborne plant diseases and the remediation of sites contaminated with a variety of chemicals. We developed genetic probes and primers that were able to detect the gacA gene in all Pseudomonas spp. isolates examined and did not detect bacteria belonging to other genera. The genus Pseudomonas contains many dissimilar species and the relationships among these species is far from clear. We demonstraed that gacA may be useful for the detection of Pseudomonas spp. in environmental samples, and may also be used to determine relatedness among bacterial isolates belonging to this genus.
Technical Abstract: The regulator gene gacA influences production of several secondary metabolites in Pseudomonas spp. Primers and a probe for the gacA gene of Pseudomonas spp. were developed and a gacA fragment was sequenced from 10 strains isolated from different plant-associated environments. PCR 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 representing 14 species that belong to 8 different genera of Gram-negative bacteria other than Pseudomonas. Furthermore, from a total of approximately 550 indigenous bacterial isolates obtained from the rhizosphere of wheat, all isolates that hybridized with the gacA probe were classified as Pseudomonas spp. by group-specific primers. Isolates that did not respond with the gacA probe and primers were identified as bacterial genera other than Pseudomonas. These results indicate that gacA can be used as a complementary genetic marker for detection of Pseudomonas spp. in environmental samples. Within the Pseudomonadaceae and Enterobacteriaceae, polymorphisms within gacA and its homologs allowed identification of six and five subclusters, respectively. These results suggest that gacA and its homologs may provide complementary markers for phylogenetic studies of Pseudomonas spp. and Gram-negative bacteria other than Pseudomonas.