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Published August 2010 | public
Journal Article

Selenium controls transcription of paralogous formate dehydrogenase genes in the termite gut acetogen, Treponema primitia

Abstract

The termite gut spirochete, Treponema primitia, is a CO_2-reductive acetogen that is phylogenetically distinct from other distantly related and more extensively studied acetogens such as Moorella thermoacetica. Research on T. primitia has revealed details about the role of spirochetes in CO_2-reductive acetogenesis, a process important to the mutualism occurring between termites and their gut microbial communities. Here, a locus of the T. primitia genome containing Wood-Ljungdahl pathway genes for CO_2-reductive acetogenesis was sequenced. This locus contained methyl-branch genes of the pathway (i.e. for the reduction of CO_2 to the level of methyl-tetrahydrofolate) including paralogous genes for cysteine and selenocysteine (Sec) variants of formate dehydrogenase (FDH) and genes for Sec incorporation. The FDH variants affiliated phylogenetically with hydrogenase-linked FDH enzymes, suggesting that T. primitia FDH enzymes utilize electrons derived directly from molecular H_2. Sub-nanomolar concentrations of selenium decreased transcript levels of the cysteine variant FDH gene. Selenium concentration did not markedly influence the level of mRNA upstream of the Sec-codon in the Sec variant FDH; however, the level of transcript extending downstream of the Sec-codon increased incrementally with increasing selenium concentrations. The features and regulation of these FDH genes are an indication that T. primitia may experience dynamic selenium availability in its H_2-rich gut environment.

Additional Information

© 2010 Society for Applied Microbiology and Blackwell Publishing Ltd. Issue published online: 7 MAR 2010. Article first published online: 7 MAR 2010. Received 9 April, 2009; accepted 11 January, 2010. This research was supported by NSF Grant DEB-0321753 (J.R.L.) and a NSF predoctoral fellowship (X.Z.). We thank John Breznak and Kwi Suk Kim for providing the T. primitia ZAS-2 genomic library, construction of which was supported by NSF Grant IBN-0114505. We thank Elizabeth Ottesen and our other laboratory colleagues for their helpful discussions and comments.

Additional details

Created:
August 23, 2023
Modified:
October 20, 2023