Immunochemical Characterization of the Capsular Polysaccharide of Azospirillum irakense KBC1
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Immunochemical Characterization of the Capsular Polysaccharide of Azospirillum irakense KBC1 Yulia P. Fedonenko • Gennady L. Burygin • Irina A. Popova • Elena N. Sigida • Alina K. Surkina Evelina L. Zdorovenko • Svetlana A. Konnova
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Received: 12 November 2012 / Accepted: 16 February 2013 / Published online: 21 March 2013 Ó Springer Science+Business Media New York 2013
Abstract The repeating unit structure of Azospirillum irakense KBC1 capsular polysaccharide (CPS) was established and was found to be identical to that of the O polysaccharide of A. irakense KBC1 lipopolysaccharide (LPS). The antigenic heterogeneity of the LPS and the CPS was shown to be related to differences in the macromolecular organization of these glycopolymers. After an immune response activation, R-form CPS molecules were found to be predominant.
Introduction The lipopolysaccharide (LPS) and the capsular polysaccharide (CPS) of the plant-growth-promoting nitrogen-fixing rhizobacteria Azospirillum are surface-associated antigens that contribute to symbiosis [14, 15]. LPS, a major cell-surface component in most Gram-negative bacteria, may have two basic forms: smooth (S) and rough (R). Both forms are made up of two structurally different domains, namely lipid A and core oligosaccharide; S-form LPS also contains O-specific polysaccharide (OPS). The Azospirillum Y. P. Fedonenko (&) G. L. Burygin I. A. Popova E. N. Sigida A. K. Surkina S. A. Konnova Institute of Biochemistry and Physiology of Plants and Microorganisms, Russian Academy of Sciences (IBPPM RAS), 13 Prospekt Entuziastov, Saratov 410049, Russia e-mail: [email protected] E. L. Zdorovenko Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, 47 Leninsky Prospekt, Moscow 119991, Russia S. A. Konnova Chernyshevsky Saratov State University, 83 Ulitsa Astrakhanskaya, Saratov 410012, Russia
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capsule bears two high-molecular-weight polysaccharide (PS)-containing compounds—an LPS–protein complex (LPPC) and a PS–lipid complex [8]. These include carbohydrates [hexoses, heptose, 2-keto-3-deoxyoctulosonic acid (KDO), and N-acetyl-D-glucosamine] and 3-hydroxylated fatty acids, all being typical LPS components. This finding permitted us to conclude that these biopolymers constitute an extracellular form of LPS, occurring as part of the capsule in several bacteria (e.g., in Escherichia coli [19]). Earlier, it was shown that azospirilla are variable in the presence of individual O and K antigens: A. brasilense Sp7 and Sp245 have serologically identical CPSs and OPSs [10], whereas the LPS and CPS of A. lipoferum Sp59b differ in immunochemical properties and in the structure of their PS constituents [16]. A. irakense strain KBC1, found associated with the roots and rhizosphere of rice in Diwaniyah (Qadisya), Iraq [6], evokes strong interest. Unlike other azospirillar strains, KBC1 can grow in the presence of 3 % NaCl and has pectate lyase activity, which offers the bacterium additional advantages for colonization of plant root tissue. In this article, we report serolog
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