Studies On The Gut Microbial Diversity And Isolation,Identification Of Chitin-degrading Bacteria From The Hindgut Of Macrotermes Barneyi

Termites are remarkably efficient in lignocellulose degradation.The process is far more efficient than wood-rooting fungi and other herbivores.Termite guts harbor a dense and diverse microbiota,which play important roles in degrading lignocellulose.Termites are classified into two large groups:lower termites and higher termites,which is based on wheather the hindgut has cellulolytic flagellates.Lower termite hinguts have flagellates,while higher termite hinguts do not have flagellates.Higher termites have diverse diets.Based on the diet,they are divided into food/grass termites,soil/humus termites and fungus-cultivating termites.Among higher termites,Macrotermitinae cultivated fungi(Termitomyces spp.)in their nests,so these termites are called fungus-cultivating termites.In some arid tropical areas fungus-cultivating termites can consume more than 90%of dead plants and play important roles in carbon cyling.Fungus-cultivating termites have evolved with multiple microbial symbionts,not only with the lignocellulose-digesting Termitomyces,but also with gut microbiota and the bacterial community in their fungus comb.Termite-fungus-bacterial symbiosis is a system,in this system the plant materials are fully degraded.To understand roles of fungus-cultivating termites of gut microbial symbionts,the gut microbial symbionts of Macrotermes barneyi were studied.Firstly,we analysised the microbial diversity(bacteria,fungi and archea)in the foregut,midgut and hindgut of M.barneyi by high-throughput sequencing.The result showed that the dominant bacterial phylum in the foregut and midgut was Proteobacteria,while the dominant bacterial phylum in the hindgut were Bacteroidetes,Firmicutes and Proteobacteria.The dominant fungal phylum in the gut was Ascomycota.However,most of archaea(85%)were unclassified.Most of the archaea which are identified are related to methanogenesis.According to Chao 1 and Shannon estimators,hindgut bacterial diversity is higher than that of foregut and midgut,midgut fungal diversity is higher than that of foregut and hindgut,forgut archaeal diversity is higher than that of midgut and hindgut.The results revealed that the microbial communities are obviously different.Sencondly,we isolated and identified chitin-degradation bacteria from the hindgut of M.barneyi by traditional methods.Using an oligotrophic medium containing chitin as the only carbon source,we obtained eight chitin-degradation bacteria based on the transparent zone around the clone.These bacteria were further studied through morphological,physiological and phylogenetic properities.The eight strains belonged to Flavobacterium,Dactylosporangium,Brevibacillus,Sphingomonas,Paenibacillus,Cellulomonas,Stenotrophomonas and Bacillus.All of them had chitinase,endoglucanase and ?-glucosidase activities,which can help us to understand how gut symbionts help termite to digest food.Finally,in the second part we got one novel strain Cellulomonas macrotermitis,a polyphasic study of the strain was performed to establish its taxonomic position.In brief,we focus on the gut microbial symbionts of M.barneyi.We analyzed the microbial diversity(bacteria,fungi and archea)in the foregut,midgut and hindgut.Then we isolated eight chitin-degradation strains from the hindgut of M.barneyi,which proves that gut symbionts help termite to digest food.We isolate a novel strain Cellulomonas macrotermitis.The above reseach indicates that there are diverse microbial symbionts in the gut of M.barneyi.These microbial symbionts may take part in carbon metabolism,nitrogen metabolism and anti-fungal defense to the host.Their specific roles to the host need further study.