Analysis of the cell surface layer ultrastructure of the oral pathogen Tannerella forsythia

Sekot, Gerhard; Posch, Gerald; Oh, Yoo Jin; Zayni, Sonja; Mayer, Heinz; Pum, Dietmar; Messner, Paul; Hinterdorfer, Peter; Schäffer, Christina

doi:10.1007/s00203-012-0792-3

Cited by 38 publications

(73 citation statements)

References 45 publications

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“…The most abundant cellular proteins targeted by this system are the S-layer proteins TfsA and TfsB, which self-assemble on the bacterium’s cell surface into a two-dimensional crystalline monolayer (Sekot et al, 2012). The T. forsythia O- glycan ( Figure 1A ) is bound to distinct Ser and Thr residues within the three-amino acid motif D(S/T)(A/I/L/M/T/V) (Posch et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

A General Protein O-Glycosylation Gene Cluster Encodes the Species-Specific Glycan of the Oral Pathogen Tannerella forsythia: O-Glycan Biosynthesis and Immunological Implications

et al. 2018

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The cell surface of the oral pathogen Tannerella forsythia is heavily glycosylated with a unique, complex decasaccharide that is O-glycosidically linked to the bacterium’s abundant surface (S-) layer, as well as other proteins. The S-layer glycoproteins are virulence factors of T. forsythia and there is evidence that protein O-glycosylation underpins the bacterium’s pathogenicity. To elucidate the protein O-glycosylation pathway, genes suspected of encoding pathway components were first identified in the genome sequence of the ATCC 43037 type strain, revealing a 27-kb gene cluster that was shown to be polycistronic. Using a gene deletion approach targeted at predicted glycosyltransferases (Gtfs) and methyltransferases encoded in this gene cluster, in combination with mass spectrometry of the protein-released O-glycans, we show that the gene cluster encodes the species-specific part of the T. forsythia ATCC 43037 decasaccharide and that this is assembled step-wise on a pentasaccharide core. The core was previously proposed to be conserved within the Bacteroidetes phylum, to which T. forsythia is affiliated, and its biosynthesis is encoded elsewhere on the bacterial genome. Next, to assess the prevalence of protein O-glycosylation among Tannerella sp., the publicly available genome sequences of six T. forsythia strains were compared, revealing gene clusters of similar size and organization as found in the ATCC 43037 type strain. The corresponding region in the genome of a periodontal health-associated Tannerella isolate showed a different gene composition lacking most of the genes commonly found in the pathogenic strains. Finally, we investigated whether differential cell surface glycosylation impacts T. forsythia’s overall immunogenicity. Release of proinflammatory cytokines by dendritic cells (DCs) upon stimulation with defined Gtf-deficient mutants of the type strain was measured and their T cell-priming potential post-stimulation was explored. This revealed that the O-glycan is pivotal to modulating DC effector functions, with the T. forsythia-specific glycan portion suppressing and the pentasaccharide core activating a Th17 response. We conclude that complex protein O-glycosylation is a hallmark of pathogenic T. forsythia strains and propose it as a valuable target for the design of novel antimicrobials against periodontitis.

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Section: Introductionmentioning

confidence: 99%

A General Protein O-Glycosylation Gene Cluster Encodes the Species-Specific Glycan of the Oral Pathogen Tannerella forsythia: O-Glycan Biosynthesis and Immunological Implications

et al. 2018

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“…Compared to other S-layer-carrying bacteria, T. forsythia ’s status is unique in two ways: it is the only Gram-negative bacterium that is known to possess a glycosylated S-layer and its S-layer is comprised of two S-layer proteins (named TfsA and TfsB) instead of just one (Sekot et al 2012). After the T. forsythia S-layer had been found to delay the host immune response, at least at the early stage of infection, (Sekot et al 2011), a detailed investigation of the bacterium’s cell surface architecture (Sekot et al 2013) and glycosylation ensued (Posch et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Tannerella forsythiastrains display different cell-surface nonulosonic acids: biosynthetic pathway characterization and first insight into biological implications

et al. 2016

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Tannerella forsythia is an anaerobic, Gram-negative periodontal pathogen. A unique O-linked oligosaccharide decorates the bacterium’s cell surface proteins and was shown to modulate the host immune response. In our study, we investigated the biosynthesis of the nonulosonic acid (NulO) present at the terminal position of this glycan. A bioinformatic analysis of T. forsythia genomes revealed a gene locus for the synthesis of pseudaminic acid (Pse) in the type strain ATCC 43037 while strains FDC 92A2 and UB4 possess a locus for the synthesis of legionaminic acid (Leg) instead. In contrast to the NulO in ATCC 43037, which has been previously identified as a Pse derivative (5-N-acetimidoyl-7-N-glyceroyl-3,5,7,9-tetradeoxy-l-glycero-l-manno-NulO), glycan analysis of strain UB4 performed in this study indicated a 350-Da, possibly N-glycolyl Leg (3,5,7,9-tetradeoxy-d-glycero-d-galacto-NulO) derivative with unknown C5,7 N-acyl moieties. We have expressed, purified and characterized enzymes of both NulO pathways to confirm these genes’ functions. Using capillary electrophoresis (CE), CE–mass spectrometry and NMR spectroscopy, our studies revealed that Pse biosynthesis in ATCC 43037 essentially follows the UDP-sugar route described in Helicobacter pylori, while the pathway in strain FDC 92A2 corresponds to Leg biosynthesis in Campylobacter jejuni involving GDP-sugar intermediates. To demonstrate that the NulO biosynthesis enzymes are functional in vivo, we created knockout mutants resulting in glycans lacking the respective NulO. Compared to the wild-type strains, the mutants exhibited significantly reduced biofilm formation on mucin-coated surfaces, suggestive of their involvement in host-pathogen interactions or host survival. This study contributes to understanding possible biological roles of bacterial NulOs.

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“…Later, Sabet et al [27] published their findings regarding the isolation, purification, and initial studies on the virulence potential of the S-layer from T. forsythia strains. SDS-PAGE analysis revealed the presence of two high molecular-mass, glyco-positive protein bands [36,37,38], which were later confirmed by our research group to be the components of the S-layer [39]. The ~135-kDa Tannerella S-layer protein TfsA and the ~152-kDa S-layer protein TfsB are encoded by the genes tfsA (TF2661-2662) and tfsB (TF2663), respectively, which are co-transcribed from a single promoter [38].…”

Section: Cellular Integritymentioning

confidence: 77%

Glycobiology Aspects of the Periodontal Pathogen Tannerella forsythia

et al. 2012

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Glycobiology is important for the periodontal pathogen Tannerella forsythia, affecting the bacterium’s cellular integrity, its life-style, and virulence potential. The bacterium possesses a unique Gram-negative cell envelope with a glycosylated surface (S-) layer as outermost decoration that is proposed to be anchored via a rough lipopolysaccharide. The S-layer glycan has the structure 4‑MeO-b-ManpNAcCONH2-(1→3)-[Pse5Am7Gc-(2→4)-]-b-ManpNAcA-(1→4)-[4-MeO-a-Galp-(1→2)-]-a-Fucp-(1→4)-[-a-Xylp-(1→3)-]-b-GlcpA-(1→3)-[-b-Digp-(1→2)-]-a-Galp and is linked to distinct serine and threonine residues within the D(S/T)(A/I/L/M/T/V) amino acid motif. Also several other Tannerella proteins are modified with the S‑layer oligosaccharide, indicating the presence of a general O‑glycosylation system. Protein O‑glycosylation impacts the life-style of T. forsythia since truncated S-layer glycans present in a defined mutant favor biofilm formation. While the S‑layer has also been shown to be a virulence factor and to delay the bacterium's recognition by the innate immune system of the host, the contribution of glycosylation to modulating host immunity is currently unraveling. Recently, it was shown that Tannerella surface glycosylation has a role in restraining the Th17-mediated neutrophil infiltration in the gingival tissues. Related to its asaccharolytic physiology, T. forsythia expresses a robust enzymatic repertoire, including several glycosidases, such as sialidases, which are linked to specific growth requirements and are involved in triggering host tissue destruction. This review compiles the current knowledge on the glycobiology of T. forsythia.

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Analysis of the cell surface layer ultrastructure of the oral pathogen Tannerella forsythia

Cited by 38 publications

References 45 publications

A General Protein O-Glycosylation Gene Cluster Encodes the Species-Specific Glycan of the Oral Pathogen Tannerella forsythia: O-Glycan Biosynthesis and Immunological Implications

A General Protein O-Glycosylation Gene Cluster Encodes the Species-Specific Glycan of the Oral Pathogen Tannerella forsythia: O-Glycan Biosynthesis and Immunological Implications

Tannerella forsythiastrains display different cell-surface nonulosonic acids: biosynthetic pathway characterization and first insight into biological implications

Glycobiology Aspects of the Periodontal Pathogen Tannerella forsythia

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