Phylogenetic analysis of the gut bacterial microflora of the fungus-growing termite Macrotermes barneyi

摘要

Termites are an extremely successful group of wood-degrading organisms and are therefore important both for their roles in carbon turnover in the environment and as potential sources of biochemical catalysts for efforts aimed at converting wood into biofuels. To contribute to the evolutional study of termite digestive symbiosis, a bacterial 16S rRNA gene clone library from the gut microbial community of the fungus-growing termite?Macrotermes barneyi?was constructed. After screening by restriction fragment length polymorphism (RFLP) analysis, 25 out of 105 clones with unique RFLP patters were sequenced and phylogenetically analyzed. Many of the clones (95%) were derived from three phyla within the domain bacteria:?Bacteroidetes,?Firmicutes?andProteobacteria. In addition, a few clones derived from?Deferribacteres,?Actinobacteria?andPlanctomycetes?were also found. No one clone affiliated with the phylum?Spirochaeteswas identified, in contrast to the case of wood-feeding termites. The phylogenetic analysis revealed that nearly half of the representative clones (11 phylotypes) formed monophyletic clusters with clones obtained from other termite species, especially with the sequences retrieved from fungus-growing termites. These results indicate that the presence of termite-specific bacterial lineages implies a coevolutional relationship of gut microbes and host termites. The remaining 14 clones formed a cluster, and there was very low sequence similarity (30 to 40%) to known 16S rRNA sequences. The 16S rRNA gene sequence data showed that the majority of the intestinal micro?ora of?M. barneyiconsisted of new, uncultured species previously unknown to microbiologists.