title: Listeria monocytogenes exopolysaccharide: origin, structure, biosynthetic machinery and c-di-GMP-dependent regulation.
abstract: Elevated levels of the second messenger c-di-GMP activate biosynthesis of an unknown exopolysaccharide (EPS) in the food-borne pathogen Listeria monocytogenes. This EPS strongly protects cells against disinfectants and desiccation, indicating its potential significance for listerial persistence in the environment and for food safety. We analyzed the potential phylogenetic origin of this EPS, determined its complete structure, characterized genes involved in its biosynthesis and hydrolysis and identified diguanylate cyclases activating its synthesis. Phylogenetic analysis of EPS biosynthesis proteins suggests that they have evolved within monoderms. Scanning electron microscopy revealed that L. monocytogenes EPS is cell surface-bound. Secreted carbohydrates represent exclusively cell-wall debris. Based on carbohydrate composition, linkage and NMR analysis, the structure of the purified EPS is identified as a β-1,4-linked N-acetylmannosamine chain decorated with terminal α-1,6-linked galactose. All genes of the pssA-E operon are required for EPS production and so is a separately located pssZ gene. We show that PssZ has an EPS-specific glycosylhydrolase activity. Exogenously added PssZ prevents EPS-mediated cell aggregation and disperses preformed aggregates, whereas an E72Q mutant in the presumed catalytic residue is much less active. The diguanylate cyclases DgcA and DgcB, whose genes are located next to pssZ, are primarily responsible for c-di-GMP-dependent EPS production.
authors: Department of Molecular Biology, University of Wyoming, Laramie, WY, 82071, USA.
authors: Volkan K
authors: VK
authors: Köseoğlu
authors: Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, 30602, USA.
authors: Christian
authors: C
authors: Heiss
authors: Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia, 30602, USA.
authors: Parastoo
authors: P
authors: Azadi
authors: Department of Chemistry, University of Wyoming, Laramie, WY, 82071, USA.
authors: Elena
authors: E
authors: Topchiy
authors: Department of Molecular Biology, University of Wyoming, Laramie, WY, 82071, USA.
authors: Zehra T
authors: ZT
authors: Güvener
authors: Department of Chemistry, University of Wyoming, Laramie, WY, 82071, USA.
authors: Teresa E
authors: TE
authors: Lehmann
authors: Department of Molecular Biology, University of Wyoming, Laramie, WY, 82071, USA.
authors: Kurt W
authors: KW
authors: Miller
authors: Department of Molecular Biology, University of Wyoming, Laramie, WY, 82071, USA.
authors: Mark
authors: M
authors: Gomelsky
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D016695:Glycosyltransferases / Q000235:genetics; D006595:Hexosamines / Q000032:analysis; D008089:Listeria monocytogenes / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism* / Q000648:ultrastructure; D008855:Microscopy, Electron, Scanning; D009876:Operon; D019761:Phosphorus-Oxygen Lyases / Q000235:genetics / Q000378:metabolism; D010802:Phylogeny; D011135:Polysaccharides, Bacterial / Q000096:biosynthesis* / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D006595:Hexosamines; D011135:Polysaccharides, Bacterial; C062025:bis(3',5')-cyclic diguanylic acid; D016695:Glycosyltransferases; C412464:PssA protein, Rhizobium leguminosarum; D019761:Phosphorus-Oxygen Lyases; C060720:diguanylate cyclase; D006152:Cyclic GMP; C002022:N-acetylmannosamine