Quantification And Localization Of Several Baterial Groups In The Gut Of Reticulitermes Chinensis Snyder And Primary Characterization Of A Lactococcus Sp. Strain

Termites are social insects distributed worldwide. There are more than3000identified species,15%of which are lower termites. As one of the most important five pests in the world, termites cause great economic harm to various plants, wood based buildings, bridges, etc. Meantime, termites play an important role in accelerating the materials circulation and optimizing the physicochemical properties of soil owning to their high-efficiency of degradation of died wood and humus in tropical and subtropical forests. The digestion and degradation of various food sources of termites are associated with the activity of diverse gut microbial symbionts.Reticulitermes chinensis Snyder is a wood-feeding termite widely distributed in China. It is considered as an important model system for the studies on the symbiotic relationship between lower termites and their intestinal symbionts, as well as their synergistic collaboration in termite lignocellulose digestion. In this study we quantified and localized several dominant culturable bacteria and one dominant bacterial group (TGI) in the gut of R. chinensis based on previous research on this termite. The physicochemical characteristics of a Lactococcus sp.(TSB-94) isolated from this termite was also analyzed. The main research results are as following:1. According to the results of Chen Wen’s research on the diversity of culturable aerobic and anaerobic bacteria in the gut of R.. chinensis,, the sequence-specific primers targeted all eubacteria and four dominant bacterial groups (Bacillus, Lactococcus, Enterobacter, Streptomyces) were designed based on their16S rRNA gene sequences. The termite gut total DNA was used as the template in the real-time quantitative PCR and the quantitative analysis showed that the most abundant cultivable aerobic and anaerobic bacteria of R. chinensis were bacteria in the genus Enterobacter (2.93%). Bacteria in the genera Lactococcus, Bacillus and Streptomyces occupied a small proportion in the total bacterial community with the percentage of0.5%,0.2%, and0.04%respectively, which indicated that these culturable bacterial groups are not the dominant groups in the whole gut bacterial community of R. chinensis Snyder.2.Termite group1(TG1) is a group of bacteria dominate in the gut of R. chinensis. Fluorescence in situ hybridization with group-specific probe (TG1-216) targetted the16S rRNA genes was used to analyze the distribution of TG1in the termite gut. The results showed that TG-1bacteria mainly distributed in one species of Hypermastigida protist Trichonympha agilis and two species of Oxymonadida protists.3. The primary physicochemical characteristics of a Lactococcus sp.(TSB-94) isolated from this termite was analyzed. Blast showed that the16S rRNA gene sequences of strain TSB-94exhibited maximum similarity (99%) with an uncultured Lactococcus clone obtained from the Reticulitermes speratus. and98%similarity with a Lactococcus.clone isolated also from R.chinensis, indicating that Lactococcus bacteria inhibit stable in the termite intestinal tract. Strain TSB-94can utilize different saccharides, including cellobiose, glucose and mannose, etc, which was speculated to be a potential and important contributor in the process of termite lignocellulose digestion. The results of this study is significant in unveiling the mechanisms of synergistic collaboration of termites and their symbionts in the process of lignocellulose digestion.