Phylogenetic analysis of 13 phylotypes of methanogens from the 25th anaerobic fungal subculture. The sequences determined in this study are marked in bold type. Accession numbers are given in parentheses. The root was determined by using Pyrolobus fumarius (× 9555) as outgroup. The topology of the tree was estimated by bootstraps, based on 1000 replications. Bootstrap values greater than 80% are shown on the internal nodes.