Affiliation:
1. Department of Biotechnology, Norwegian University of Science and Technology (NTNU), N-7491 Trondheim, Norway
2. SINTEF Materials and Chemistry, Department of Biotechnology, SINTEF, N-7034 Trondheim, Norway
Abstract
ABSTRACT
Alginate is an industrially widely used polysaccharide produced by brown seaweeds and as an exopolysaccharide by bacteria belonging to the genera
Pseudomonas
and
Azotobacter
. The polymer is composed of the two sugar monomers mannuronic acid and guluronic acid (G), and in all these bacteria the genes encoding 12 of the proteins essential for synthesis of the polymer are clustered in the genome. Interestingly, 1 of the 12 proteins is an alginate lyase (AlgL), which is able to degrade the polymer down to short oligouronides. The reason why this lyase is associated with the biosynthetic complex is not clear, but in this paper we show that the complete lack of AlgL activity in
Pseudomonas fluorescens
in the presence of high levels of alginate synthesis is toxic to the cells. This toxicity increased with the level of alginate synthesis. Furthermore, alginate synthesis became reduced in the absence of AlgL, and the polymers contained much less G residues than in the wild-type polymer. To explain these results and other data previously reported in the literature, we propose that the main biological function of AlgL is to degrade alginates that fail to become exported out of the cell and thereby become stranded in the periplasmic space. At high levels of alginate synthesis in the absence of AlgL, such stranded polymers may accumulate in the periplasm to such an extent that the integrity of the cell is lost, leading to the observed toxic effects.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Reference42 articles.
1. Alginate Lyase (AlgL) Activity Is Required for Alginate Biosynthesis in
Pseudomonas aeruginosa
2. Bjerkan, T. M., C. L. Bender, H. Ertesvåg, F. Drabløs, M. K. Fakhr, L. A. Preston, G. Skjåk-Bræk, and S. Valla. 2004. The Pseudomonas syringae genome encodes a combined mannuronan C-5-epimerase and O-acetyl hydrolase, which strongly enhances the predicted gel-forming properties of alginates. J. Biol. Chem.279:28920-28929.
3. Blatny, J. M., T. Brautaset, H. C. Winther-Larsen, K. Haugan, and S. Valla. 1997. Construction and use of a versatile set of broad-host-range cloning and expression vectors based on the RK2 replicon. J. Bacteriol.63:370-379.
4. Boyd, A., M. Ghosh, T. B. May, D. Shinabarger, R. Keogh, and A. M. Chakrabarty. 1993. Sequence of the algL gene of Pseudomonas aeruginosa and purification of its alginate lyase product. Gene131:1-8.
5. Chitnis, C. E., and D. E. Ohman. 1993. Genetic analysis of the alginate biosynthetic gene cluster of Pseudomonas aeruginosa shows evidence of an operonic structure. Mol. Microbiol.8:583-593.
Cited by
76 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献