Behavior of two Tannerella forsythia strains and their cell surface mutants in multispecies oral biofilms

Abstract

SummaryAs a member of subgingival multispecies biofilms, Tannerella forsythia is commonly associated with periodontitis. The bacterium has a characteristic cell surface (S‐) layer modified with a unique O‐glycan. Both the S‐layer and the O‐glycan were analyzed in this study for their role in biofilm formation by employing an in vitro multispecies biofilm model mimicking the situation in the oral cavity. Different T. forsythia strains and mutants with characterized defects in cell surface composition were incorporated into the model, together with nine species of select oral bacteria. The influence of the T. forsythia S‐layer and attached glycan on the bacterial composition of the biofilms was analyzed quantitatively using colony‐forming unit counts and quantitative real‐time polymerase chain reaction, as well as qualitatively by fluorescence in situ hybridization and confocal laser scanning microscopy. This revealed that changes in the T. forsythia cell surface did not affect the quantitative composition of the multispecies consortium, with the exception of Campylobacter rectus cell numbers. The localization of T. forsythia within the bacterial agglomeration varied depending on changes in the S‐layer glycan, and this also affected its aggregation with Porphyromonas gingivalis. This suggests a selective role for the glycosylated T. forsythia S‐layer in the positioning of this species within the biofilm, its co‐localization with P. gingivalis, and the prevalence of C. rectus. These findings might translate into a potential role of T. forsythia cell surface structures in the virulence of this species when interacting with host tissues and the immune system, from within or beyond the biofilm.

Immune response profiling of primary monocytes and oral keratinocytes to different Tannerella forsythia strains and their cell surface mutants

“…As previous studies analyzing the cytokine release induced by T. forsythia focused only on the ATCC 43037 type strain, we here provide a first description of the differential immune response to different strains of T. forsythia , namely ATCC 43037 and UB4. UB4 was previously found to have an advantage over T. forsythia ATCC 43037 in planktonic as well as biofilm growth and shows a varied localization in a multispecies biofilm, suggesting an altered adaptation to this environmental condition . Here, we additionally show that both strains are highly invasive in HOK and elicit differential immune responses in monocytes as well as in keratinocytes.…”

“…For T. forsythia , several virulence factors have been described; among them are components of the cell surface . The bacterium possesses a characteristic surface (S‐) layer covering the entire cell . This is composed of the two S‐layer proteins TfsA and TfsB, both of which are modified with a complex, branched dekasaccharide O ‐glycosidically linked to multiple serine and threonine residues within a D(S/T)(A/I/L/M/T/V) amino acid target motif .…”

“…30,31 The two T. forsythia strains ATCC 43037 and UB4 vary not only in the terminal nonulosonic acid of the otherwise identical O-glycan, 29 but also in displaying different growth characteristics, monospecies biofilm formation and behavior in a multispecies biofilm consortium. 25 Both the T. forsythia S-layer and the attached glycan, especially the nonulosonic acids, were found to facilitate monospecies biofilm formation and the localization of T. forsythia within a multispecies biofilm. 25,29 The glycosylated S-layer of T. forsythia ATCC 43037 was shown to suppress the production of proinflammatory cytokines in U937 macrophages and human gingival fibroblasts, 32 to modulate the immune response through recognition by the macrophage inducible C-type lectin (Mincle) 33 and facilitate adhesion to and invasion of gingival epithelial cells.…”

“…25 Both the T. forsythia S-layer and the attached glycan, especially the nonulosonic acids, were found to facilitate monospecies biofilm formation and the localization of T. forsythia within a multispecies biofilm. 25,29 The glycosylated S-layer of T. forsythia ATCC 43037 was shown to suppress the production of proinflammatory cytokines in U937 macrophages and human gingival fibroblasts, 32 to modulate the immune response through recognition by the macrophage inducible C-type lectin (Mincle) 33 and facilitate adhesion to and invasion of gingival epithelial cells. 22 Outer membrane vesicles of T. forsythia ATCC 43037, naturally carrying the intact glycosylated S-layer, were found to induce expression of TNFα and IL-8 in U937 macrophages, and IL-6, IL-8 and MCP-1 in primary human periodontal ligament fibroblasts.…”

“…[21][22][23][24] The bacterium possesses a characteristic surface (S-) layer covering the entire cell. 25 This is composed of the two S-layer proteins TfsA and TfsB, 26 both of which are modified with a complex, branched dekasaccharide O-glycosidically linked to multiple serine and threonine residues within a D(S/T)(A/I/L/M/T/V) amino acid target motif. 27 Protein glycosylation is a post-transcriptional modification employed by numerous pathogenic bacteria to modulate the host immune response, and glycosylated appendages like pili or flagella play a vital role in orchestrating invasion and infection.…”