Taxonomy of spirochetes

More than 75 "species-level" phylotypes of spirochete bacteria belonging to the genus Treponema reside within the human oral cavity. The majority of these oral treponeme phylotypes correspond to as-yet-uncultivated taxa or strains of uncertain standing in taxonomy. Here, we analyze phylogenetic and taxonomic relationships between oral treponeme strains using a multilocus sequence analysis (MLSA) scheme based on the highly conserved 16S rRNA, pyrH, recA, and flaA genes. We utilized this MLSA scheme to analyze genetic data from a curated collection of oral treponeme strains (n ϭ 71) of diverse geographical origins. This comprises phylogroup 1 (n ϭ 23) and phylogroup 2 (n ϭ 48) treponeme strains, including all relevant American Type Culture Collection reference strains. The taxonomy of all strains was confirmed or inferred via the analysis of ca. 1,450-bp 16S rRNA gene sequences using a combination of bioinformatic and phylogenetic approaches. Taxonomic and phylogenetic relationships between the respective treponeme strains were further investigated by analyzing individual and concatenated flaA (1,074-nucleotide [nt]), recA (1,377-nt), and pyrH (696-nt) gene sequence data sets. Our data confirmed the species differentiation between Treponema denticola (n ϭ 41) and Treponema putidum (n ϭ 7) strains. Notably, our results clearly supported the differentiation of the 23 phylogroup 1 treponeme strains into five distinct "species-level" phylotypes. These respectively corresponded to "Treponema vincentii" (n ϭ 11), Treponema medium (n ϭ 1), "Treponema sinensis" (Treponema sp. IA; n ϭ 4), Treponema sp. IB (n ϭ 3), and Treponema sp. IC (n ϭ 4). In conclusion, our MLSA-based approach can be used to effectively discriminate oral treponeme taxa, confirm taxonomic assignment, and enable the delineation of species boundaries with high confidence.IMPORTANCE Periodontal diseases are caused by persistent polymicrobial biofilm infections of the gums and underlying tooth-supporting structures and have a complex and variable etiology. Although Treponema denticola is strongly associated with periodontal diseases, the etiological roles of other treponeme species/phylotypes are less well defined. This is due to a paucity of formal species descriptions and a poor understanding of genetic relationships between oral treponeme taxa. Our study directly addresses these issues. It represents one of the most comprehensive analyses of oral treponeme strains performed to date, including isolates from North America, Europe, and Asia. We envisage that our results will greatly facilitate future metagenomic efforts aimed at characterizing the clinical distributions of oral treponeme species/phylotypes, helping investigators to establish a more detailed understanding of their etiological roles in periodontal diseases and other infectious diseases. Our results are also directly relevant to various polymicrobial tissue infections in animals, which also involve treponeme populations.

Section: Resultssupporting

confidence: 91%

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confidence: 99%

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confidence: 99%

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Multilocus Sequence Analysis of Phylogroup 1 and 2 Oral Treponeme Strains

Huo

Chan

Lacap-Bugler

et al. 2017

“…The genome of B. burgdorferi comprises a linear chromosome carrying genes needed for cell maintenance and replication (the occurrence of genes encoding proteins for metabolic purposes is very limited, likely as an adaptation to a strictly parasitic life style) and a large number of circular and linear plasmids which carry the genes encoding most of the outer surface proteins (Osp), which are involved in interactions with host and vector (35). Borrelia species have been delineated using DNA-DNA association, 23S-5S intergenic spacer (IGS), and 16S sequences and multilocus sequence analysis (MLSA) (34,36,37). A number of methods of strain typing and genotyping B. burgdorferi have been used (38).…”

Section: Diversity Of Borrelia Burgdorferimentioning

confidence: 99%

Evolutionary Aspects of Emerging Lyme Disease in Canada

Ogden

Feil

Leighton

et al. 2015

fIn North America, Lyme disease (LD) is a tick-borne zoonosis caused by the spirochete bacterium Borrelia burgdorferi sensu stricto, which is maintained by wildlife. Tick vectors and bacteria are currently spreading into Canada and causing increasing numbers of cases of LD in humans and raising a pressing need for public health responses. There is no vaccine, and LD prevention depends on knowing who is at risk and informing them how to protect themselves from infection. Recently, it was found in the United States that some strains of B. burgdorferi sensu stricto cause severe disease, whereas others cause mild, self-limiting disease. While many strains occurring in the United States also occur in Canada, strains in some parts of Canada are different from those in the United States. We therefore recognize a need to identify which strains specific to Canada can cause severe disease and to characterize their geographic distribution to determine which Canadians are particularly at risk. In this review, we summarize the history of emergence of LD in North America, our current knowledge of B. burgdorferi sensu stricto diversity, its intriguing origins in the ecology and evolution of the bacterium, and its importance for the epidemiology and clinical and laboratory diagnosis of LD. We propose methods for investigating associations between B. burgdorferi sensu stricto diversity, ecology, and pathogenicity and for developing predictive tools to guide public health interventions. We also highlight the emergence of B. burgdorferi sensu stricto in Canada as a unique opportunity for exploring the evolutionary aspects of tick-borne pathogen emergence.

“…These investigations clearly verified that the termite hindguts are an enormous reservoir of novel spirochete species. Recently, more than 40 different spirochetal phylotypes were recognized in one termite species (28) in comparison to less than 30 well-characterized and named spirochetes of the genera Spirochaeta and Treponema (32). Corresponding to the phylogenetic positions of spirochetal clones obtained from termite gut contents, it was previously speculated that all termite spirochetes represent a separate phylogenetic branch of the treponemes (2,36).…”

Section: Vol 72 2006mentioning

confidence: 99%

Spirochaeta coccoides sp. nov., a Novel Coccoid Spirochete from the Hindgut of the Termite Neotermes castaneus

Dröge

Fröhlich

Radek

et al. 2006

A novel spirochete strain, SPN1, was isolated from the hindgut contents of the termite Neotermes castaneus. The highest similarities (about 90%) of the strain SPN1 16S rRNA gene sequence are with spirochetes belonging to the genus Spirochaeta, and thus, the isolate could not be assigned to the so-called termite clusters of the treponemes or to a known species of the genus Spirochaeta. Therefore, it represents a novel species, which was named Spirochaeta coccoides. In contrast to all other known validly described spirochete species, strain SPN1 shows a coccoid morphology and is immotile. The isolated strain is obligately anaerobic and ferments different mono-, di-, and oligosaccharides by forming formate, acetate, and ethanol as the main fermentation end products. Furthermore, strain SPN1 is able to grow anaerobically with yeast extract as the sole carbon and energy source. The fastest growth was obtained at 30°C, the temperature at which the termites were also grown. The cells possess different enzymatic activities that are involved in the degradation of lignocellulose in the termite hindgut, such as ␤-D-glucosidase, ␣-L-arabinosidase, and ␤-D-xylosidase. Therefore, they may play an important role in the digestion of breakdown products from cellulose and hemicellulose in the termite gut.Spirochetes are distinguished from all other bacteria by their unique morphology and mechanism of motility due to the helical shape of the cells and the location of the flagella (axial filaments). They form a coherent phylogenetic group at the phylum level. These axial filaments, ultrastructurally similar to bacterial flagella, are attached to the cell poles and wrapped around the protoplasmic cylinder, which consists of the cytoplasmic and nuclear regions. The flagella and the protoplasmic cylinder are surrounded by a multilayered membrane called the outer sheath or outer cell envelope (9). Comparisons of 16S rRNA sequences demonstrate that the spirochetes represent a monophyletic phylum within the bacteria (35). Spirochetes are widespread in several environments, either as freeliving cells, mainly in marine and limnic sediments, or host associated as commensals or parasites of animals and humans.One of the spirochetal habitats is the digestive tract of termites and wood-eating cockroaches. Termites have developed a unique hindgut flora consisting of bacteria, archaea, flagellates, and yeasts. This symbiotic microbial community supports the decomposition of complex organic compounds and thus enables the termites to feed on wood or soil (6, 13, 21, 44). Spirochetes are one of the most abundant bacteria present in the gut fluid of termites, (36). Spirochetes of several sizes (3 to 100 m in length; 0.2 to 1.0 m in width) are consistently present in the hindguts of all termites (5). Whereas most spirochetes usually exist free-living in the gut fluid, they have also been found as ectosymbionts attached to the surfaces of protists, such as Mixotricha paradoxa, that inhabit the gut of the lower wood-eating termite Mastotermes darwinien...