Pectinolytic bacteria Pectobacterium spp. and Dickeya spp. that cause blackleg and soft rot are responsible for high economic losses in potato production under different climate conditions worldwide.
Currently, there are 8 species in the genus Dickeya: D. aquatica, D. chrysanthemi, D. dadantii, D. dianthicola, D. fangzhongdai, D. paradisiaca, D. solani and D. zeae, and 9 species in the genus Pectobacterium: P. aroidearum, P. atrosepticum, P. betavasculorum, P. cacticidum, P. carotovorum, P. parmentieri, P. peruviense, P. polaris and P. wasabiae.
Development of disease symptoms, caused by bacteria on potato and other plant is the result of plant–microbe interaction and depends on cultivar susceptibility, strain virulence and the presence of favorable environmental conditions. The main virulence factors of pectinolytic bacteria are plant cell wall degrading enzymes (pectinases, cellulases and proteases).
Due to the activities of enzymes bacteria can degrade plant cell wall components and cause maceration of the plant tissue. The other factors that play an important role in the disease symptoms development are lipopolysaccharides (LPS), which are important for bacterial adhesion and attachment to plant cells, and what affects the later interaction.
The lipopolysaccharides are glycoconjugates, which are components of the outer membrane of Gram-negative bacteria. The LPS possess three chemically, biologically, biosynthetically and genetically distinct domains: the lipid A, core oligosaccharide and O-polysaccharide. The lipid A is covalently linked to the core oligosaccharide, which is substituted by hetero-polysaccharide called O-polysaccharide. The O-polysaccharide (O-antigen, OPS) is the outermost domain of lipopolysaccharides. The OPS is characterized by high structural diversity, which may occur not only between species, but also between bacterial strains. It consists of number of repeating oligosaccharide units containing 2-8 monosaccharide residues. The presence of non-carbohydrate substituents like phosphate, amino acids, acetyl or formamide groups is also possible [1,2].
In our study the structures of O-polysaccharides of LPS produced by several Dickeya and Pectobacterium strains have been assigned usisng chemical methods (sugar and methylation analyses), gas chromatography (GC), liquid chromatography (HPLC), nuclear magnetic resonance spectroscopy (NMR), mass spectrometry (MS), and gas or liquid chromatography coupled to mass spectrometry (GC-MS or LC-MS).
- Knirel, Y.A. Structure of O-Antigens. In Bacterial Lipopolysaccharides (Eds. Knirel Y. A., Valvano M. A.). Springer-Verlag, Vienna, 2011; pp 41-116.
- Raetz, C.R.; Whitfield, C. Lipopolysaccharide endotoxins. Annu. Rev. Biochem. 2002, 71, 635–700.