左图为白蚁，右上图为原虫，右下图为细菌Pseudotrichonympha grassii在细胞内的照片
据11月13日的《科学》杂志报道说，用于消化木材的生物化学能力即神秘又在加工生物燃料上有着很高的需求。科学家们如今描绘了一种成为白蚁以消化木材作为其唯一食物来源基础的复杂的寄生虫体内含有寄生虫的关系。
许多共生性微生物居住在白蚁的肠道内协助白蚁消化木材。其中的一种是原虫，它本身又是细菌Pseudotrichonympha grassii 的一个宿主。Yuichi Hongoh及其同僚对P. grassii 的完整的基因组进行了序列测定。他们报道说， 其独特的基因组序列披露了该种细菌能够固定大气中的氮，再循环废弃物中的氮并为它们自己以及它们的原虫宿主制造氨基酸的能力。（生物谷Bioon.com）
生物谷推荐原始出处：
Science 14 November 2008: 1108-1109.
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,2,3Todd D. Taylor,2,3 Toshiaki Kudo,1 Yoshiyuki Sakaki,2Atsushi Toyoda,2,4Masahira Hattori,2,5Moriya 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.
1 Ecomolecular Biorecycling Science Research Team, RIKEN Advanced Science Institute, Saitama 351-0198, Japan.
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.
