| Termites are typical organisms in the nature which can usually thrive on nitrogen-poor diet by feeding on pure cellulose from live or died wood.In wood-feeding termites,whose food may contain as little as 0.05%nitrogen(dry weight basis),the nitrogen content of its organs is 110 g/kg.Previous research shows that symbionts in the gut of termites play an important role in nitrogen fixation and recycling.Except recycling nitrogen from uric acid,N2 fixation can supply up to 60%of the nitrogen in termite biomass by symbiotic microorganisms.Reticulitermes chinese Snyder is a wood-feeding lower termite widely distributed in China.Primary studies showed that there were plenty of diverse prokaryotes and flagellates inhabiting the intestinal tract of this termite.In this study,the diversity of nitrogen-fixing organisms in the symbiotic intestinal microflora of Reticulitermes chinese Snyder was investigated with culture-independent techniques.Fragments of the nifH genes,which encode the dinitrogenase reductase,were directly amplified from the DNA of the mixed microbial population in the termite hindgut with four pair of primers corresponding to the conserved regions of the amino acid sequences of dinitrogenase reductase.Four corresponding nifH gene libraries were established.Clones which represent different gene types analyzed by RFLP were selected for sequencing.A large number of the termite nifH sequences were most closely related to those of bacteria affiliated with Spirochaetes,Firmicutes,Termite-group1,and Methanogenic Archaea. Phylogenetic analysis of nifH also revealed that the dinitrogenase reductases obtained from Reticulitermes chinese were most closely related to those of nifH retrieved from wood-feeding lower termites.In contrast,only few of the dinitrogenase reductases were most closely related to those of nifH originated from higher termites,indicating a correlation between the diversity of symbiotic microbiota and their termite hosts.
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