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1.
Fig. 4.

Fig. 4. From: Tannerella forsythia strains display different cell-surface nonulosonic acids: biosynthetic pathway characterization and first insight into biological implications.

SDS-PAGE gels (12%) of purified recombinant enzymes of the (A) CMP-Pse biosynthesis pathway from T. forsythia ATCC 43037 and (B) CMP-Leg biosynthesis pathway from T. forsythia FDC 92A2/UB4.

Valentin Friedrich, et al. Glycobiology. 2017 Apr;27(4):342-357.
2.
Fig. 7.

Fig. 7. From: Tannerella forsythia strains display different cell-surface nonulosonic acids: biosynthetic pathway characterization and first insight into biological implications.

SDS-PAGE analysis of T. forsythia parent, NulO-deficient, and complemented strains. (A) CBB stained SDS-PAGE (7.5% gel) of whole cell extracts from T. forsythia ATCC 43037, ATCC 43037 ΔpseC and the complemented strain ATCC 43037 ΔpseCcomp, and (B) T. forsythia UB4 wild-type, UB4 ΔlegC and the complemented strain UB4 ΔlegCcomp. For both T. forsythia ATCC 43037 ΔpseC and UB4 ΔlegC, a downshift of the S-layer protein bands (TfsA and TfsB) could be observed, which was reverted in the complemented strains.

Valentin Friedrich, et al. Glycobiology. 2017 Apr;27(4):342-357.
3.
Fig. 5.

Fig. 5. From: Tannerella forsythia strains display different cell-surface nonulosonic acids: biosynthetic pathway characterization and first insight into biological implications.

CE analysis of the reaction products obtained by the incubation of UDP-GlcNAc (IP) upon sequential addition of PseB-His6, forming UDP-2-acetamido-2,6-dideoxy-β-l-arabino-hexos-4-ulose (IIP); PseC-MBP, forming UDP-4-amino-4,6-dideoxy-β-L-AltNAc (IIIP); PseH-His6, forming UDP-2,4-diacetamido-2,4,6-trideoxy-β-l-altro-pyranose (IVP) and PseG-MBP, releasing UDP. Lastly, the combined action of PseI-His6 and H. pylori PseF convert 2,4-diacetamido-2,4,6-trideoxy-β-l-altro-pyranose (VP) via Pse5,7Ac2 (VIP) to CMP-Pse5,7Ac2 (VIIP). Subscript “P” indicates intermediates from the CMP-Pse biosynthesis pathway.

Valentin Friedrich, et al. Glycobiology. 2017 Apr;27(4):342-357.
4.
Fig. 8.

Fig. 8. From: Tannerella forsythia strains display different cell-surface nonulosonic acids: biosynthetic pathway characterization and first insight into biological implications.

Knockout of pseC and legC decreases biofilm formation of T. forsythia ATCC 43037 and T. forsythia UB4 cells, respectively. (A) Biofilm formation in T. forsythia ATCC 43037 wild-type compared to ATCC 43037 ΔpseC and the complemented strain ATCC 43037 ΔpseCcomp. (B) Biofilm formation in T. forsythia UB4 wild-type compared to UB4 ΔlegC and the complemented strain T. forsythia UB4 ΔlegCcomp. Data represent mean values ± SD of at least four independent experiments with four replicates each and were analyzed by the unpaired Student's t-test. Asterisks indicate significant differences (**P < 0.01).

Valentin Friedrich, et al. Glycobiology. 2017 Apr;27(4):342-357.
5.
Fig. 1.

Fig. 1. From: Tannerella forsythia strains display different cell-surface nonulosonic acids: biosynthetic pathway characterization and first insight into biological implications.

(A) Structures of Sia and Sia-like sugars (NulOs). Sialic acid (Neu5Ac), legionaminic acid (Leg5,7Ac2) and pseudaminic acids (Pse5,7Ac2 and Pse5Am7Gra) are shown. To note, Pse5Am7Gra is found as the terminal sugar of the S-layer glycan in T. forsythia ATCC 43037. For reference, the nine carbon atoms of Sia are numbered, and the structure of the NHAc group is shown in the boxed inset. (B) Schematic drawing of the structure of the S-layer O-glycan in T. forsythia ATCC 43037 (amended from )). This figure is available in black and white in print and in color at Glycobiology online.

Valentin Friedrich, et al. Glycobiology. 2017 Apr;27(4):342-357.
6.
Fig. 3.

Fig. 3. From: Tannerella forsythia strains display different cell-surface nonulosonic acids: biosynthetic pathway characterization and first insight into biological implications.

Phylogenetic clusters of selected microbial NulO synthase homologs. Based on the prediction of NulO sugar type by ), a distance-based neighbor joining tree calculated from the amino acid sequences of NulO synthase enzymes places Tanf_01240 of T. forsythia type strain ATCC 43037 in a phylogenetic clade of pseudaminic acid synthases, while BFO_1066 of strain FDC 92A2/UB4 is clustered with Leg synthases (bootstrap values shown at relevant nodes). Green denotes Leg synthases, red Neu synthases and blue Pse synthases. This figure is available in black and white in print and in color at Glycobiology online.

Valentin Friedrich, et al. Glycobiology. 2017 Apr;27(4):342-357.
7.
Fig. 6.

Fig. 6. From: Tannerella forsythia strains display different cell-surface nonulosonic acids: biosynthetic pathway characterization and first insight into biological implications.

CE analysis of the reaction products obtained by incubation of (A) BFO_1074-His6 with UDP-GlcNAc (IP, red traces) and GDP-GlcNAc (IL, green traces) as substrate. Formation of product (GDP-2-acetamido-2,6-dideoxy-α-d-xylo-hexos-4-ulose (IIL)) could only be observed with GDP-GlcNAc (IL), confirming that BFO_1074-His6 is a LegB homolog that utilizes GDP-linked substrates. (B) GDP-GlcNAc (IL) with both the dehydratase BFO_1074-His6 (LegB) and the aminotransferase His6-BFO_1073 (LegC), resulted in the formation of GDP-4-amino-4,6-dideoxy-α-d-GlcNAc (IIIL). In the overnight reaction, a conversion of roughly 75% could be achieved. (C) GDP-2,4-diacetamido-2,4,6-trideoxy-α-d-glucopyranose (IVL) with the hydrolyzing 2-epimerase BFO_1065 (LegG). Complete release of GDP from the substrate could be observed after 15 min of incubation. Subscripts “P” and “L” indicate intermediates from the CMP-Pse and CMP-Leg biosynthesis pathway, respectively. This figure is available in black and white in print and in color at Glycobiology online.

Valentin Friedrich, et al. Glycobiology. 2017 Apr;27(4):342-357.
8.
Fig. 2.

Fig. 2. From: Tannerella forsythia strains display different cell-surface nonulosonic acids: biosynthetic pathway characterization and first insight into biological implications.

Experimentally confirmed enzymatic steps (in green) in T. forsythia strains ATCC 43037 (left) and FDC 92A2/UB4 (right) corresponding to the CMP-Pse and CMP-Leg biosynthetic pathways as elucidated in H. pylori and C. jejuni, respectively (, ). In T. forsythia, pathways will deviate at some point to produce the unique NulO derivatives found in our strains, such as Pse5Am7Gra. These deviations would be anticipated to occur either within the NulO biosynthetic pathway or post CMP-NulO biosynthesis. Red, blue and orange highlight enzymatic steps that introduce the stereochemical differences between the two pathways and also indicate the positions altered for both hexose intermediates and final NulO. The assignment of roman numerals to each compound is consistent with label designations found throughout the text. Subscripts “P” and “L” indicate intermediates from the CMP-Pse and CMP-Leg biosynthesis pathway, respectively. For simplicity, all sugars except for the NulOs are shown in 4C1 form. This figure is available in black and white in print and in color at Glycobiology online.

Valentin Friedrich, et al. Glycobiology. 2017 Apr;27(4):342-357.
9.
Fig. 9.

Fig. 9. From: Tannerella forsythia strains display different cell-surface nonulosonic acids: biosynthetic pathway characterization and first insight into biological implications.

Possible biological roles of the NulOs of the T. forsythia S-layer glycan. Representing the terminal sugars on the outermost surface structure of T. forsythia strains, Pse or Leg could have several functions. As previous studies have found the terminal trisaccharide of the S-layer glycan to be involved in the modulation of cytokine release and the suppression of Th17 responses, we hypothesize that the different NulOs displayed by T. forsythia strains are implicated in this phenomenon. Apart from the effect on monospecies biofilm formation described in this paper, the terminal NulOs are likely to play a role in the bacterium's interactions with other species of the subgingival microbiota. Furthermore, they could exert an influence on how the bacterium attaches to periodontal surfaces and how it invades host tissue. The variation of the NulO type among various T. forsythia strains may reflect a special ‘fit’ with only certain hosts and/or microenvironments. This figure is available in black and white in print and in color at Glycobiology online.

Valentin Friedrich, et al. Glycobiology. 2017 Apr;27(4):342-357.

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