Diversity and Taxonomy of Methanogens

TLDR: This work has shown that methane production is a ubiquitous, defining characteristic of methanogens, a group of microbes that is phylogenetically distinct from eukaryotes and true bacteria.

Abstract: The production of methane is a ubiquitous, defining characteristic of methanogens. The production of methane or any other hydrocarbon as a major catabolic product is unique to this group of microbes, which share many other characteristics that are not common among other microbes. Phylogenetically, methanogens are Archaeobacteria (Woese et al., 1978), a group of microbes that are distinguished from true bacteria by a number of characteristics, including the possession of membrane lipids composed of isoprenoids ether-linked to glycerol or other carbohydrates (De Rosa and Gambacorta, 1988; Jones et al., 1987; Langworthy, 1985), a lack of peptidoglycan containing muramic acid (Kandier and Hippe, 1977), and distinctive ribosomal RNA sequences (Balch et al., 1979; Woese, 1987). This group also includes some extreme halophiles and some extremely thermophilic, sulfur-dependent microbes (Woese, 1987) and is phylogenetically distinct from eukaryotes and true bacteria (Figure 1.1).