Laboratory of Malaria Research, National Institutes of Health, Building 4, Bethesda, Maryland 20892, USA.
Genetic analysis of the alginate biosynthetic gene cluster of Pseudomonas aeruginosa shows evidence of an operonic structure
Article first published online: 27 OCT 2006
Volume 8, Issue 3, pages 583–590, May 1993
How to Cite
Chitnis, C. E. and Ohman, D. E. (1993), Genetic analysis of the alginate biosynthetic gene cluster of Pseudomonas aeruginosa shows evidence of an operonic structure. Molecular Microbiology, 8: 583–590. doi: 10.1111/j.1365-2958.1993.tb01602.x
- Issue published online: 27 OCT 2006
- Article first published online: 27 OCT 2006
- Received 16 July, 1992; revised 6 January, 1993; accepted 18 January, 1993
Strains of Pseudomonas aeruginosa causing pulmonary infections in cystic fibrosis patients have an unusual mucoid phenotype because of production of the capsule-like exopolysaccharide, alginate. Transcriptional activation of algD, the first gene of a large alginate biosynthetic gene cluster, is associated with conversion to the alginate-producing (Alg+) phenotype. In this study, we examined the regulation of alginate genes immediately downstream of algD. Mutants of the Alg+ strain FRD1 were constructed by gene replacement with defined Tn501 (8.2 kb) insertions in the alginate biosynthetic gene cluster, resulting in an Alg− phenotype. The Alg+ phenotype of these mutants was restored by integration of narrow-host-range plasmids containing DNA fragments from P. aeruginosa that reconstructed a continuous alginate gene cluster. A broad-host-range plasmid containing the entire alginate gene cluster except for the terminal gene, algA was unable to complement an aIG::Tn501 mutant unless algA was transcribed from a second plasmid. This indicated that any Tn501 insertion in the cluster was polar on downstream alginate genes. Northern blot hybridization experiments also showed that a transposon insertion downstream of algD adversely affected algG and algA transcription. These results provided evidence that the alginate biosynthetic gene cluster has an operonic structure and is cotranscribed from the algD promoter.