The article "Methanogens: Reevaluation of a Unique Biological Group" by W. E. Balch, G. E. Fox, L. J. Magrum, C. R. Woese, and R. S. Wolfe, published in the Journal of Bacteriology, presents a comprehensive reevaluation of the taxonomic classification and phylogenetic relationships of methanogens. The authors use 16S rRNA oligonucleotide catalogs to compare the genetic diversity of methanogens, revealing that they form a distinct and coherent group phylogenetically distant from typical bacteria. This phylogenetic analysis challenges the traditional taxonomic classification of methanogens, which was based on morphology and other phenotypic characteristics. The study outlines a new taxonomic scheme for methanogens, dividing them into three orders: Methanobacteriales, Methanococcales, and Methanomicrobiales. Each order contains multiple families and genera, reflecting the diverse morphological and genetic characteristics of the methanogens. The authors provide detailed descriptions of the cell wall structure and lipid composition of methanogens, which differ significantly from those of typical bacteria. For example, methanogens lack saponifiable lipids and contain ether-linked polyisoprenoid (branched) chain lipids, which are characteristic of their unique metabolism. The article also discusses the growth techniques and media used for cultivating methanogens, emphasizing the importance of anaerobic conditions and specific nutrient requirements. The authors conclude that the new taxonomic treatment is supported by evidence from cell wall structure, lipid composition, and genetic analysis, providing a more accurate and phylogenetically informed classification of methanogens.The article "Methanogens: Reevaluation of a Unique Biological Group" by W. E. Balch, G. E. Fox, L. J. Magrum, C. R. Woese, and R. S. Wolfe, published in the Journal of Bacteriology, presents a comprehensive reevaluation of the taxonomic classification and phylogenetic relationships of methanogens. The authors use 16S rRNA oligonucleotide catalogs to compare the genetic diversity of methanogens, revealing that they form a distinct and coherent group phylogenetically distant from typical bacteria. This phylogenetic analysis challenges the traditional taxonomic classification of methanogens, which was based on morphology and other phenotypic characteristics. The study outlines a new taxonomic scheme for methanogens, dividing them into three orders: Methanobacteriales, Methanococcales, and Methanomicrobiales. Each order contains multiple families and genera, reflecting the diverse morphological and genetic characteristics of the methanogens. The authors provide detailed descriptions of the cell wall structure and lipid composition of methanogens, which differ significantly from those of typical bacteria. For example, methanogens lack saponifiable lipids and contain ether-linked polyisoprenoid (branched) chain lipids, which are characteristic of their unique metabolism. The article also discusses the growth techniques and media used for cultivating methanogens, emphasizing the importance of anaerobic conditions and specific nutrient requirements. The authors conclude that the new taxonomic treatment is supported by evidence from cell wall structure, lipid composition, and genetic analysis, providing a more accurate and phylogenetically informed classification of methanogens.