Comparative Studies On The Diversity Of Intestinal Symbiotic Bacteria Between Two Different Wood-feeding Termites

Wood-feeding termites are one of the decomposers that can degrade cellulose effectively. As a typical symbiotic system in nature the symbiotic relationship between termites and their intestinal microorganisms are fasinating topics for researchers in the world all the time. The studies on the symbiotic microorganisms are not only useful for the declaration of the symbiotic mechanisms between termites and their gut microorganisms but also the declaration of mechamisms of cellulose degradation.In this paper, we studied the diversity of symbiotic bacteria in the gut of two kinds of wood-feeding termites:Reticulitermes chinensis Snyder that represents wood-feeding lower termites and Nasutitermes sp. that represents wood-feeding higher termites. The results form a basis for further studies on the clarification of the mechanisms of cellulose degradation in the future. The main results are as following:1. A bacterial 16S rRNA gene library was established from the PCR product amplified from the DNA extracted from the whole gut of Nasutitermes sp.with the universal bacterial 16S rRNA gene primers. In total 73 bacterial 16S rRNA genes were obtained from 419 random selected clones. Phylogenetic analysis of these 16S rRNA genes showed that the most dominant symbiotic bacterial group in the gut of Nasutitermes sp was Spirochaetes, which occupied 65.8% of the total bacterial clones. Fibrobacteres and Bacteroidales were also major bacterial groups that occupied 16.5% and 4.5%, respectively in total bacterial clones. In addition to these, there are some clones affiliated with Planctomycetes and Firmicutes.2. A bacterial 16S rRNA gene library was established from the PCR product amplified from the DNA extracted from the whole gut of Reticulitermes chinensis Snyder.with the universal bacterial 16S rRNA gene primers. In total 150 bacterial 16S rRNA genes were obtained from 602 random selected clones. Phylogenetic analysis of these 16S rRNA genes showed that the major symbiotic bacterial clones in the gut of Reticulitermes chinensis were affiliated with Spirochaetes (42.3%), Termite group 1 (19.3%), Proteobacteria (10.3%), Firmicutes (7.1%) and Bacteroidales (6.8%). In addition to those, there were still bacteria affiliated with Planctomycets and Actinobacteria, indicating a high baceterial diversity in the gut of Reticulitermes chinensis.3. MPN counting of the intestinal aerobic and facultive anaerobic bacteria in the gut of Reticulitermes chinensis showed that the number of aerobic and facultive anaerobic bacteria in every termite was 9.25 X 105 cells.4. Rarefaction analysis of the bacterial clones obtained from the two bacterial 16S rRNA genes showed that the number of selected clones were enough to cover the diversity of bacteria in the two termite guts, indicating the reliability of the diversity analysis.The results of this study showed that there were significant differences between the bacterial diversity and community structure in the gut of Nasutitermes sp.and Reticulitermes chinensis. In comparison with the bacterial diversity reported from the other termites, we speculated that the diversity and community structure of symbiotic bacteria in the intestinal tract of termites may be associated with the physiological conditions of digestive tract and the metabolic requirements of the termites, as well as whether or not exist flagellates in the gut of host termites.