Structure and Biosynthesis of Two Exopolysaccharides Produced by Lactobacillus johnsonii FI9785*

  1. Arjan Narbad
  1. From the Gut Health and Food Safety Programme, Institute of Food Research, Colney, Norwich NR4 7UA, United Kingdom,
  2. the §Department of Food Engineering, Faculty of Engineering, Bayburt University, Bayburt 69000, Turkey, and
  3. the Analytical Sciences Unit, Institute of Food Research,
  4. the Food and Health Programme, Institute of Food Research, and
  5. the **School of Biomedical Sciences, University of Nottingham, Nottingham NG7 2UH, United Kingdom
  1. 3 To whom correspondence should be addressed: Gut Health and Food Safety Programme, Institute of Food Research, Colney, Norwich, NR4 7UA, United Kingdom. Tel.: 44-1603-255284; Fax: 44-1603-507723; E-mail: Melinda.Mayer{at}ifr.ac.uk.

Background: Bacterial cell surface polysaccharides are important in pathogenesis, cell adhesion, and protection against harsh environments.

Results: Two novel exopolysaccharide (EPS) structures were identified in Lactobacillus johnsonii.

Conclusion: The eps cluster is essential for production of both EPS, but epsE is required only for the heteropolymer.

Significance: This study will guide functional analysis of EPS in survival and colonization of gut commensals.

Abstract

Exopolysaccharides were isolated and purified from Lactobacillus johnsonii FI9785, which has previously been shown to act as a competitive exclusion agent to control Clostridium perfringens in poultry. Structural analysis by NMR spectroscopy revealed that L. johnsonii FI9785 can produce two types of exopolysaccharide: EPS-1 is a branched dextran with the unusual feature that every backbone residue is substituted with a 2-linked glucose unit, and EPS-2 was shown to have a repeating unit with the following structure: -6)-α-Glcp-(1–3)-β-Glcp-(1–5)-β-Galf-(1–6)-α-Glcp-(1–4)-β-Galp-(1–4)-β-Glcp-(1-. Sites on both polysaccharides were partially occupied by substituent groups: 1-phosphoglycerol and O-acetyl groups in EPS-1 and a single O-acetyl group in EPS-2. Analysis of a deletion mutant (ΔepsE) lacking the putative priming glycosyltransferase gene located within a predicted eps gene cluster revealed that the mutant could produce EPS-1 but not EPS-2, indicating that epsE is essential for the biosynthesis of EPS-2. Atomic force microscopy confirmed the localization of galactose residues on the exterior of wild type cells and their absence in the ΔepsE mutant. EPS2 was found to adopt a random coil structural conformation. Deletion of the entire 14-kb eps cluster resulted in an acapsular mutant phenotype that was not able to produce either EPS-2 or EPS-1. Alterations in the cell surface properties of the EPS-specific mutants were demonstrated by differences in binding of an anti-wild type L. johnsonii antibody. These findings provide insights into the biosynthesis and structures of novel exopolysaccharides produced by L. johnsonii FI9785, which are likely to play an important role in biofilm formation, protection against harsh environment of the gut, and colonization of the host.

Footnotes

  • 1 Supported by the Turkish Ministry of Education.

  • 2 Recipient of instrument funding from BBSRC Grant BB/C510924 and a contribution from Varian Inc. (Agilent Technologies).

  • * This work was supported in part by Biotechnology and Biological Science Research Council (BBSRC) Strategic Core Grants BB/J004529/1 and BB/J004545/1 and the European Union FP7 TORNADO program.

  • Received August 2, 2013.
  • Revision received September 4, 2013.

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  1. The Journal of Biological Chemistry 288, 31938-31951.
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  3. All Versions of this Article:
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