Diversity Of The Culturable Aerobic Bacteria In The Gut Of Nasutitermes Sp.&Primary Characterization Of A Curtobacterium Strain Isolated From The Gut Of Reticulitermes Chinensis Snyder

Termites, with numerous species, usually distributed in tropical and subtropical regions and play a vital role in nature and human society. Each year, economic damage with hundreds of millions dollars was caused by wood-feeding termites. Wood-feeding termites degrade lignocellulose efficiently with the cooperation of their symbiotic intestinal microbiota. Different types of wood-feeding termites have different symbiotic microorganisms in the intestine because of the variation of biological characteristics, including the feeding habits and habitats. Lignocellulose is the most abundant renewable resource on the planet, which makes it great significant if we could utilize the cellulase and lignocellulose-degrading microorganisms for the development of biomass energy. Nasutitermes sp. is one of the representatives of wood-feeding higher termites. Previous studies showed that there are various cellulase and cellulose-decomposing bacteria in termite hindgut through metagenomic analysis of the Nasutitermes intestinal microorganisms. In this paper, we studied diversity of culturable bacteria in the gut of Nasutitermes sp. under aerobic conditions, and preliminarily identified a novel species of the genus Curtobacterium, strain TS-56, which was isolated from wood-feeding lower termites, Reticulitermes chinensis Snyder. These works laid the foundation for the further illustration of the symbiotic relationship between wood-feeding termites and their gut microbes, and the mining and utilization of novel microbial resources for the biofuel industry. The main results of the study are as following:1. Aerobic bacterial strains in the hindgut of a Nasutitermes species that distributed in Wuzhi mountain of Hainan province of China were isolated and preliminarily identified using culture dependent method for the first time, and the structure and diversity of the gut microbiota was preliminarily evaluated. Four media, including1/3TSB,1/4NB, CMC-Na, and1/5LB were employed. In total60aerobic bacterial strains were isolated from the gut of Nasutitermes sp. and were identified preliminary, based on morphology and molecular biological characteristics of the16S rRNA gene. ARDRA analysis (amplified rDNA restriction analysis) showed that these isolates can be classified into42ARDRA pattens. Bacterial strains clearly characterized belonged to14bacterial genera, including the genus Bacillus, Ochrobacterium, Stenotrophmonas, Microbacterium, Paenibacillus, Serratia, Acinetobacter, Janibacter, Lysinibacillus, Arthrobacter, Citricoccus, Kerstersia, Raoutella, Arsenicicoccus.16S rDNA sequence alignment showed that three isolates could be novel species, since their16S rDNA sequences showed similarity lower than98%compared with bacteria retrieved from GenBank database. Most of the isolates showed high similarities in16S rDNA sequences compared with the other bacteria. Bacteria of four genera were isolated from the CMC-Na medium, indicating that these bacteria may have the capability for cellulose degradation.2. In this study, a Gram-positive, non-motile, light yellow, irregular short rode-shaped (0.4-0.6μm in diameter,0.6-1.0μm in length)bacterium, strain TS-56isolated from the gut of Reticulitermes chinensis Snyder, was preliminarily characterized. Strain TS-56was not salinity tolerant. Growth of strain TS-56occurred at20-35℃(optimum,30℃), at pH4.0-7.0(optimum, pH5.0). On the basis of16S rRNA gene sequence similarity, strain TS-56was shown to belong to the genus Curtobacterium of the class Microbacteriaceae, the highest sequence similarity of16S rDNA is97%compared with other bacteria in GenBank database. The amino acids in the cell wall of strain TS-56were ornithine, glutamic, alanine, glycine and homoserine, etc. The polar lipid profile contained disphosphatidyl glycerol (DPG), phosphatidyl glycerol (PG), phosphatidyl inositol (PI) and phosphatidyl choline (PC). DNA of the type strain had a G+C content of mol67.4%. Other chemotaxonomic data also supported the affiliation of strain TS-56to the genus Curtobacterium. Based on the phylogenetic properties and phenotypic distinctiveness, strain TS-56represents a novel species of the genus Curtobacterium.