Development of quasi-multicellular bodies of Treponema denticola

A new class of protein sensor links spirochete pleomorphism, persistence, and chemotaxis

IMPORTANCE

A new class of bacterial protein sensors monitors intracellular levels of S-adenosylmethionine to modulate cell morphology, chemotaxis, and biofilm formation. Simultaneous regulation of these behaviors enables bacterial pathogens to survive within their niche. This sensor, exemplified by Treponema denticola CheWS, is anchored to the chemotaxis array and its sensor domain is located below the chemotaxis rings. This position may allow the sensor to directly interact with the chemotaxis histidine kinase CheA. Collectively, these data establish a critical role of CheWS in pathogenesis and further illustrate the impact of studying non-canonical chemotaxis proteins.

Comparative Analysis of Brucepastera parasyntrophica gen. nov., sp. nov. and Teretinema zuelzerae gen. nov., comb. nov. (Treponemataceae) Reveals the Importance of Interspecies Hydrogen Transfer in the Energy Metabolism of Spirochetes

Most members of the family Treponemataceae (Spirochaetales) are associated with vertebrate hosts. However, a diverse clade of uncultured, putatively free-living treponemes comprising several genus-level lineages is present in other anoxic environments. The only cultivated representative to date is Treponema zuelzerae, isolated from freshwater mud. Here, we describe the isolation of strain RmG11 from the intestinal tract of cockroaches. The strain represents a novel genus-level lineage of Treponemataceae and is metabolically distinct from T. zuelzerae. While T. zuelzerae grows well on various sugars, forming acetate and H₂ as major fermentation products, strain RmG11 grew poorly on glucose, maltose, and starch, forming mainly ethanol and only small amounts of acetate and H₂. In contrast to the growth of T. zuelzerae, that of strain RmG11 was strongly inhibited at high H₂ partial pressures but improved considerably when H₂ was removed from the headspace. Cocultures of strain RmG11 with the H₂-consuming Methanospirillum hungatei produced acetate and methane but no ethanol. Comparative genomic analysis revealed that strain RmG11 possesses only a single, electron-confurcating hydrogenase that forms H₂ from NADH and reduced ferredoxin, whereas T. zuelzerae also possesses a second, ferredoxin-dependent hydrogenase that allows the thermodynamically more favorable formation of H₂ from ferredoxin via the Rnf complex. In addition, we found that T. zuelzerae utilizes xylan and possesses the genomic potential to degrade other plant polysaccharides. Based on phenotypic and phylogenomic evidence, we describe strain RmG11 as Brucepastera parasyntrophica gen. nov., sp. nov. and Treponema zuelzerae as Teretinema zuelzerae gen. nov., comb. nov. IMPORTANCE Spirochetes are widely distributed in various anoxic environments and commonly form molecular hydrogen as a major fermentation product. Here, we show that two closely related members of the family Treponemataceae differ strongly in their sensitivity to high hydrogen partial pressure, and we explain the metabolic mechanisms that cause these differences by comparative genome analysis. We demonstrate a strong boost in the growth of the hydrogen-sensitive strain and a shift in its fermentation products to acetate during cocultivation with a H₂-utilizing methanogen. Our results add a hitherto unrecognized facet to the fermentative metabolism of spirochetes and also underscore the importance of interspecies hydrogen transfer in not-obligately-syntrophic interactions among fermentative and hydrogenotrophic guilds in anoxic environments.

Characteristics of Treponema denticola lipooligosaccharide in presence of hemin and quorum-sensing molecule

OBJECTIVES

The study aimed to examine the diverse bioactivity of lipooligosaccharide extracted from T. denticola cultured in the presence of hemin and quorum-sensing inhibitor.

DESIGN

T. denticola was cultured in the presence or absence hemin or 2(5 H)-furanone, and lipooligosaccharide from T. denticola cultured in various conditions was extracted using an extraction kit. To investigate bioactivity of the lipooligosaccharide, human gingival fibroblasts (HGFs) were treated with the extracted lipooligosaccharide in the presence or absence of Tannerella forsythia lipopolysaccharide. The induction of cytokine expressions was investigated by real-time RT-PCR and ELISA, and the signaling pathway was examined by immunoblotting. To investigate antagonistic mechanisms of the lipooligosaccharide, HGFs were cotreated with fluorescence-labeled T. forsythia lipopolysaccharide and the extracted lipooligosaccharide. Binding of T. forsythia lipopolysaccharide to the cell was analyzed by a flow cytometer.

RESULTS

Lipooligosaccharide induced a low level of cytokine expression at high concentration of hemin or 2(5 H)-furanone. Lipooligosaccharide extracted from T. denticola cultured in higher concentration of hemin and 2(5 H)-furanone had a greater inhibitory effect on induction of cytokine expression by T. forsythia lipopolysaccharide. Further, lipooligosaccharide inhibited the activation of NF-κB and mitogen-activated protein kinase signaling pathways by T. forsythia lipopolysaccharide. Lipooligosaccharide inhibited the binding of T. forsythia lipopolysaccharide to HGFs in the presence of CD14 and LBP.

CONCLUSIONS

The characteristics of T. denticola lipooligosaccharide may be altered by bacterial communication and host factors.