Isolation and Detection of Methanogens from the Gut of Higher Termites

Abstract

Four strains of hydrogenotrophic methanogens showing narrow ranges of utilizable substrates were isolated in pure cultures from the guts of various feeding groups of (phylogenetically) higher termites. An analysis of the 16S rRNA gene sequence revealed that three strains were closely related to Methanobacterium bryantii (>99% nucleotide identity), the other to the genus Methanobrevibacter. The latter was related to a clone identified previously from the gut of a higher termite without cultivation (clone MPn19) and Methanobrevibacter arboriphilicus (99.0 and 97.9% nucleotide identity, respectively) but distinct from the species identified in lower termites. The specific detection of related methanogens in the gut population by nested-PCR indicated that every termite harbored the species of Methanobrevibacter. However, the methanogen related to the Methanobacterium strain was not detected in two termite species from which the Methanobacterium strains were isolated, suggesting that they are less prevalent in the gut community.