The Diversity Of Termite Symbiotic Bacteria From Odontotermes Guts And Their Potential Lignocellulytic Functions

A series of environmental and energy problems has become one of the global problems to be solved urgently due to the heavy dependence of fossil fuels.The efficient use of biomass resources,represented by lignocellulose,is a critical breakthrough in the realization of environmental and energy sustainable development.Termites and their intestinal microbial symbiosis system has a unique and efficient degrading ability to transform lignocellulose,which has aroused widespread concerns in various fields of scientific research.Odontotermes is common type species of fungus-growing termites,which account for more than half of the whole fungus-growing termite’s population.It has a symbiotic relationship with fungus and their intestinal bacteria.Its symbiotic system could degrade almost all lignocellulose.Symbiotic fungus plays an important role in degrading lignocellulose.In recent years,amounts of gene resources of cellulase and hemicellulase were discovered in symbiotic bacteria.It implied that bacteria from termite guts also plays a vital role in degrading lignocellulose and becomes a research hotspot gradually.but the diversity and lignocellulytic functions of their symbiotic bacteria still remains unknown.In this study,Odonotermes longgignathus 、 Odonotermes formosanus 、Odonotermes sp.YN14 from Xishuangbanna area were selected as research objects.The composition of Odontotermes symbiotic bacteria were clarified by 16 s rRNA highthroughput sequencing.Bacteria with the function of degrading lignocellulose were isolated by in vitro culturing.The ability of isolated bacteria on enzyme producing also be analyzed by quantitative and qualitative assay.The bacterium with the potential industrial application was selected and studied in order to analyze its preliminary application in industry.The main results of this study are summarized as follows:(1)Odontotermes longiganthus、Odontotermes formounsans and Odontotermes sp.YN14 from the Xishuangbanna region were selected.The composition of their symbiotic bacteria were clarified by 16 s rRNA high-throughput sequencing.Results showed that the dominant bacterial community were Bacteroidetes,Firmicutes and Proteobacteria.It implied that the diversity and composition of bacteria were influenced by the revolution of termite and its habitat,it exists a large amount of lignocellulytic enzyme and bacteria resources waiting to be discovered.(2)32 strains of bacteria with the ability in degrading lignocellulose were screened in vitro from Odontoterms guts.It shows that the symbiotic bacteria were involved in degrading lignocellulose.The composition of lignocellulytic bacteria were exploered,enterobacter were the dominant bacterial community.Hafnia and Leclercia were selected from termtie’s gut for the first time.A strain with prominent ability in degrading xylan was determined by biochemical test and molecular identification,it was identified as Citrobacter murliniae,and it is the first time to estimate lignocellulytic ability of that strain.(3)The xylanase producing conditions of C.murliniae were optimized.The optimized activity were increased 2.17 fold compares unoptimized one.The rate of saccharification of rice straw was 8.50% at 48 h.Through the analysis of decolorization rate on azo dyes by strain ZF1567,it has the highest decolorization rate on Remazol Brilliant Blue R and Reactive Black which was 90.53% and 92.7%,respectively.It shows that the strain ZF1567 has a great ability of application prospect in the treatment of printing and dyeing wastewater.In summarized,it is the first time,the composition of three species of Odontotermes on the region of Xishuangbanna were clarified by 16 s rRNA highthroughput sequencing.Bacteria with the function of degrading lignocellulose were isolated to clarify the composition of culturable lignocellulytic bacteria from Odontotermes guts.Obtained valuable strain with potential in industrial application.It provided basic theory and microorganism resources in solving the problem of industrial scale of lignocellulose efficient transformation.