Symbiotic spirochetes in the termite hindgut: phylogenetic identification of ectosymbiotic spirochetes of oxymonad protists

Abstract

Some species of protists inhabiting the hindgut of lower-termites have a large number of ectosymbiotic spirochetes on the cell surface. The phylogenetic positions of the ectosymbiotic spirochetes of three oxymonad protists, Dinenympha porteri in the gut of Reticulitermes speratus, and Pyrsonympha sp. and Dinenympha sp. in Hodotermopsis sjoestedti, were investigated without cultivation of these organisms. Protist fractions carefully collected with a micromanipulator were used as templates for the amplification of small subunit ribosomal RNA genes (SSU rDNA). The phylogenetic tree inferred from the nucleotide sequences of the SSU rDNA showed that they were affiliated with the Treponema cluster of spirochetes and they were divided into two clusters. One was grouped together with the spirochetal sequences reported previously from the gut of termites and the other was related to the Treponema bryantii subgroup of treponemes (denoted as termite Treponema clusters I and II, respectively). Whole-cell in situ hybridization using a fluorescent-labeled oligonucleotide probe specific for the group of sequences in cluster II identified most of the ectosymbiotic spirochetes of the oxymonad protists in the gut of R. speratus and H. sjoestedti. However, not all of the ectosymbiotic spirochetes could be detected by means of this cluster II group-specific probe and the population of ectosymbiotic spirochetes of cluster II was different among the oxymonad species. In the case of D. porteri, an oligonucleotide probe specific for one member of cluster II recognized a portion of the ectosymbiotic spirochetes of cluster II, and their population was also different depending on the cell-type of D. porteri in terms of the attachment of ectosymbiotic spirochetes. The results indicate that the spirochetes of cluster II and probably those of a part of cluster I can be assigned to ectosymbiotic species of oxymonad protists and that the population of ectosymbiotic spirochetes associated with a single protist consists of at least three species of phylogenetically distinct spirochetes.

Acetogenesis from H2plus CO2and nitrogen fixation by an endosymbiotic spirochete of a termite-gut cellulolytic protist

“…This phylogenetic relationship implies an evolution from ecto-to endosymbioses, as is also suggested in Bacteroidales endo-and ectosymbionts of termite-gut protists (43). The ectosymbiotic attachments of treponemes onto the protist cells have been often observed (27,28), and they are hypothesized to catalyze reductive acetogenesis (12). Termite-gut microbial communities harbor a variety of endoand ectosymbiotic relationships and thus provide attractive models for comparative studies to understand how these symbiotic relationships have been established, adapted, and coevolved.…”

“…The previously described termite Treponema clusters I and II (26) are indicated. Ectosymbiont sequences are identified from termite-gut oxymonad protists (27). Clones RsaTcA12, RsaTcA15, HsjTcA88, and HsjTcB75 were obtained from cell suspensions of Trichonympha protists (39).…”

“…The termite specimens were collected and maintained as described previously (25,27). Termites were introduced into an anaerobic chamber (Bactron Model II; Sheldon Manufacturing Inc.) with an O 2 -free atmosphere of N 2 /H 2 /CO 2 (80/10/10, vol/vol/vol) and all of the following sample preparations were performed under the anoxic condition at ambient temperature.…”

“…Phylogenetic analyses (Fig. 2) revealed that the sequences of the endosymbionts were derived from spirochetes of the genus Treponema and belonged to the previously defined termite Treponema cluster II (26), which consists of the ectosymbionts attached to the cell surface of gut protists as far as their localizations were examined (27,28). This cluster formed a clade with saccharolytic treponemes that contained Treponema brennaborense, an isolate from a digital dermatitis ulcer of a cow (29), as a close cultured relative, but distantly related to the termite Treponema cluster I that comprises isolates and clone sequences from termite guts.…”

Symbionts of the gut flagellate Staurojoenina sp. from Neotermes cubanus represent a novel, termite-associated lineage of Bacteroidales: description of ‘Candidatus Vestibaculum illigatum’

“…The presence of special attachment sites on the cell envelope of the flagellates (Smith & Arnott, 1974;Tamm, 1980;Radek et al, 1992Radek et al, , 1996 indicate tight interactions, but only in the case of Mixotricha paradoxa (Cleveland & Grimstone, 1964) and a devescovinid flagellate (Tamm, 1982), has a function of the epibionts in the motility of the host cell been demonstrated. Apart from some epibiotic spirochaetes (Iida et al, 2000;Noda et al, 2003) of several other gut flagellates, the epibionts of M. paradoxa (Wenzel et al, 2003) are also among the few instances where the phylogenetic affiliation of the prokaryotic partner has been substantiated (Dolan, 2001). …”