Genome analyses of uncultured TG2/ZB3 bacteria in ‘Margulisbacteria’ specifically attached to ectosymbiotic spirochetes of protists in the termite gut
We investigated the phylogenetic diversity, localisation and metabolism of an uncultured bacterial clade, Termite Group 2 (TG2), or ZB3, in the termite gut, which belongs to the candidate phylum ‘Margulisbacteria’. We performed 16S rRNA amplicon sequencing analysis and detected TG2/ZB3 sequences in...
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Published in | The ISME Journal Vol. 13; no. 2; pp. 455 - 467 |
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Main Authors | , , , , , , , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
London
Nature Publishing Group UK
01.02.2019
Nature Publishing Group |
Subjects | |
Online Access | Get full text |
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Summary: | We investigated the phylogenetic diversity, localisation and metabolism of an uncultured bacterial clade, Termite Group 2 (TG2), or ZB3, in the termite gut, which belongs to the candidate phylum ‘Margulisbacteria’. We performed 16S rRNA amplicon sequencing analysis and detected TG2/ZB3 sequences in 40 out of 72 termite and cockroach species, which exclusively constituted a monophyletic cluster in the TG2/ZB3 clade. Fluorescence in situ hybridisation analysis in lower termites revealed that these bacteria are specifically attached to ectosymbiotic spirochetes of oxymonad gut protists. Draft genomes of four TG2/ZB3 phylotypes from a small number of bacterial cells were reconstructed, and functional genome analysis suggested that these bacteria hydrolyse and ferment cellulose/cellobiose to H
2
, CO
2
, acetate and ethanol. We also assembled a draft genome for a partner
Treponema
spirochete and found that it encoded genes for reductive acetogenesis from H
2
and CO
2
. We hypothesise that the TG2/ZB3 bacteria we report here are commensal or mutualistic symbionts of the spirochetes, exploiting the spirochetes as H
2
sinks. For these bacteria, we propose a novel genus, ‘
Candidatus
Termititenax’, which represents a hitherto uncharacterised class-level clade in ‘Margulisbacteria’. Our findings add another layer, i.e., cellular association between bacteria, to the multi-layered symbiotic system in the termite gut. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 1751-7362 1751-7370 |
DOI: | 10.1038/s41396-018-0297-4 |