Editor: Yaacov Okon
Mutation in a d-alanine–d-alanine ligase of Azospirillum brasilense Cd results in an overproduction of exopolysaccharides and a decreased tolerance to saline stress
Version of Record online: 19 NOV 2008
© 2008 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved
FEMS Microbiology Letters
Volume 290, Issue 2, pages 236–246, January 2009
How to Cite
Jofré, E., Fischer, S., Príncipe, A., Castro, M., Ferrari, W., Lagares, A. and Mori, G. (2009), Mutation in a d-alanine–d-alanine ligase of Azospirillum brasilense Cd results in an overproduction of exopolysaccharides and a decreased tolerance to saline stress. FEMS Microbiology Letters, 290: 236–246. doi: 10.1111/j.1574-6968.2008.01421.x
- Issue online: 8 DEC 2008
- Version of Record online: 19 NOV 2008
- Received 20 October 2008; accepted 27 October 2008.First published online 19 November 2008.
- Azospirillum brasilense;
- d-alanine–d-alanine ligase;
- salinity tolerance;
- cell division
Bacteria of the genus Azospirillum are free-living nitrogen-fixing, rhizobacteria that are found in close association with plant roots, where they exert beneficial effects on plant growth and yield in many crops of agronomic importance. Unlike other bacteria, little is known about the genetics and biochemistry of exopolysaccharides in Azospirillum brasilense. In an attempt to characterize genes associated with exopolysaccharides production, we generated an A. brasilense Cd Tn5 mutant that showed exopolysaccharides overproduction, decreased tolerance to saline conditions, altered cell morphology, and increased sensitivity to detergents. Genetic characterization showed that the Tn5 was inserted within a ddlB gene encoding for a d-alanine–d-alanine ligase, and located upstream of the ftsQAZ gene cluster responsible for cell division in different bacteria. Heterologous complementation of the ddlB Tn5 mutant restored the exopolysaccharides production to wild-type levels and the ability to grow in the presence of detergents, but not the morphology and growth characteristics of the wild-type bacteria, suggesting a polar effect of Tn5 on the fts genes. This result and the construction of a nonpolar ddlB mutant provide solid evidence of the presence of transcriptional coupling between a gene associated with peptidoglycan biosynthesis and the fts genes required to control cell division.