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Bacterial Symbionts of Termite Gut Flagellates

其他書名	Cospeciation and Nitrogen Fixation in the Gut of Dry-wood Termites
出版	Philipps-Universität Marburg, 2008
URL	http://books.google.com.hk/books?id=MdxHAQAACAAJ&hl=&source=gbs_api

註釋The subject of this thesis is the symbiosis between flagellates and bacteria in the gut of dry-wood termites (Kalotermitidae). In a series of studies, the evolution of devescovinid flagellates and their bacterial symbionts was elucidated, and the physiological basis of the symbiosis was investigated, with a focus on nitrogen fixation. Devescovinid flagellates are the dominant flagellates in the gut of Kalotermitidae. Species-pure suspensions of devescovinid flagellates (Devescovina and Metadevescovina species) from a wide range of termite species in the family Kalotermitidae were isolated with micropipettes. Ribosomal RNA gene sequences of the host flagellates and their bacterial symbionts were obtained using a full-cycle-rRNA approach. Phylogenetic analysis showed that Devescovina spp. present in many species of Kalotermitidae form a monophyletic group. They were consistently associated with a distinct lineage of ectosymbionts, which form a monophyletic group among the Bacteroidales. The well-supported congruence of their phylogenies documented strict cospeciation of flagellates and their ectosymbionts, which were temporarily classified as "Candidatus Armantifilum devescovinae". Nevertheless, the complete incongruence between the phylogenies of devescovinid flagellates and Kalotermitidae (COII genes) demonstrated horizontal transfer of flagellates among several species of Kalotermitidae. The presence of filamentous "A. devescovinae" on the surface of Devescovina spp. was corroborated with scanning electron microscopy and fluorescent in situ hybridization. However, several Metadevescovina species, which form a sister group of Devescovina spp., did not possess Bacteroidales ectosymbionts. Moreover, a combination of molecular analysis and electron microscopy led to a correction of the previously overestimated diversity of Metadevescovina species in the gut of termite Incisitermes marginipennis. In contrast to the Bacteroidales ectosymbionts, the endosymbionts of Deves.