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Genes for selenium dependent and independent formate dehydrogenase in the gut microbial communities of three lower, wood‐feeding termites and a wood‐feeding roach
Author(s) -
Zhang Xinning,
Matson Eric G.,
Leadbetter Jared R.
Publication year - 2011
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2010.02330.x
Subject(s) - biology , hindgut , rhinotermitidae , formate dehydrogenase , acetogenesis , microbiology and biotechnology , botany , bacteria , genetics , enzyme , biochemistry , midgut , cofactor , methanogenesis , larva
Summary The bacterial Wood–Ljungdahl pathway for CO 2 ‐reductive acetogenesis is important for the nutritional mutualism occurring between wood‐feeding insects and their hindgut microbiota. A key step in this pathway is the reduction of CO 2 to formate, catalysed by the enzyme formate dehydrogenase (FDH). Putative selenocysteine‐ (Sec) and cysteine‐ (Cys) containing paralogues of hydrogenase‐linked FDH (FDH H ) have been identified in the termite gut acetogenic spirochete, Treponema primitia , but knowledge of their relevance in the termite gut environment remains limited. In this study, we designed degenerate PCR primers for FDH H genes ( fdhF ) and assessed fdhF diversity in insect gut bacterial isolates and the gut microbial communities of termites and cockroaches. The insects examined herein represent three wood‐feeding termite families, Termopsidae , Kalotermitidae and Rhinotermitidae (phylogenetically ‘lower’ termite taxa); the wood‐feeding roach family Cryptocercidae (the sister taxon to termites); and the omnivorous roach family Blattidae . Sec and Cys FDH H variants were identified in every wood‐feeding insect but not the omnivorous roach. Of 68 novel alleles obtained from inventories, 66 affiliated phylogenetically with enzymes from T. primitia . These formed two subclades (37 and 29 phylotypes) almost completely comprised of Sec‐containing and Cys‐containing enzymes respectively. A gut cDNA inventory showed transcription of both variants in the termite Zootermopsis nevadensis (family Termopsidae ). The gene patterns suggest that FDH H enzymes are important for the CO 2 ‐reductive metabolism of uncultured acetogenic treponemes and imply that the availability of selenium, a trace element, shaped microbial gene content in the last common ancestor of dictyopteran, wood‐feeding insects, and continues to shape it to this day.