Genome of an Endosymbiont Coupling N2 Fixation to Cellulolysis Within Protist Cells in Termite Gut
Yuichi Hongoh,1*
Vineet K. Sharma,2,3*
Tulika Prakash,2,3
Satoko Noda,1
Hidehiro Toh,2,3
Todd D. Taylor,2,3
Toshiaki Kudo,1
Yoshiyuki Sakaki,2
Atsushi Toyoda,2,4
Masahira Hattori,2,5
Moriya Ohkuma1
Termites harbor diverse symbiotic gut microorganisms, the majority
of which are as yet uncultivable and their interrelationships
unclear. Here, we present the complete genome sequence of the
uncultured Bacteroidales endosymbiont of the cellulolytic protist
Pseudotrichonympha grassii, which accounts for 70% of the bacterial
cells in the gut of the termite
Coptotermes formosanus. Functional
annotation of the chromosome (1,114,206 base pairs) unveiled
its ability to fix dinitrogen and recycle putative host nitrogen
wastes for biosynthesis of diverse amino acids and cofactors,
and import glucose and xylose as energy and carbon sources.
Thus, nitrogen fixation and cellulolysis are coupled within
the protist's cells. This highly evolved symbiotic system probably
underlies the ability of the worldwide pest termites
Coptotermes to use wood as their sole food.
2 RIKEN Genomic Sciences Center, Kanagawa 230-0045, Japan.
3 MetaSystems Research Team, RIKEN Advanced Science Institute, Kanagawa 230-0045, Japan.
4 Comparative Genomics Laboratory, National Institute of Genetics, Shizuoka 411-8540, Japan.
5 Department of Computational Biology, Graduate School of Frontier Sciences, University of Tokyo, Chiba 277-8561, Japan.
* These authors contributed equally to this work.
Present address: Faculty of Fisheries, Nagasaki University, Nagasaki 852-8521, Japan.
Present address: Toyohashi University of Technology, Aichi 441-8580, Japan.
To whom correspondence should be addressed. E-mail: yhongo{at}riken.jp; atoyoda{at}lab.nig.ac.jp
