Phylogenetic and morphological diversity of Bacteroidales members associated with the gut wall of termites

The microbial community adherent directly or indirectly to the gut wall of termites is distinct from that of the other habitats in the gut. The bacterial 16S rRNA genes were identified from the fractionated gut walls of two termite species, Hodotermopsis sjoestedti and Neotermes koshunensis, and compared with those previously identified from Reticulitermes speratus. Surprisingly, the bacterial constituents were almost entirely different among the termites at the phylotype level (the criterion of the phylotype was > 97% nucleotide identity). Bacteria in the order Bacteroidales, which were commonly abundant symbionts on gut walls, were phylogenetically analyzed. They were dispersed in a number of clusters formed by phylotypes from the guts of various termites. In situ hybridization with probes specific for some phylotypes and a phylogenetic cluster detected the cells of several Bacteroidales members with a significant variety of cell morphology in the gut wall fractions, which reflects the phylogenetic diversity of this order.