Phylogeny of symbiotic methanogens in the gut of the termite Reticulitermes speratus.

The phylogeny of a symbiotic methanogen inhabiting the gut of a lower termite. Reticulitermes speratus, was analysed without cultivation. The small subunit ribosomal RNA gene (ssrDNA) and a 640-bp portion of the gene encoding subunit A of methyl coenzyme M reductase (mcrA) were amplified from a mixed-population DNA of the termite gut by polymerase chain reaction and cloned. The nucleotide sequence of the ssrDNA and the predicted amino acid sequence of the mcrA product were compared with those of the known methanogens. Both comparisons indicated that the termite symbiotic methanogen belonged to the order Methanobacteriales but was distinct from the known members of this order.