How are bacteria different from archaea?

While bacteria and archaea are both single-celled prokaryotes that lack membrane-bound nuclei and intracellular organelles, they represent two fundamentally distinct evolutionary lineages. Their separation is based on significant differences in their chemistry, physiology, and genetic makeup.123

Key differences include:

• Cell Wall Composition: Virtually all bacteria contain peptidoglycan in their cell walls, a substance entirely absent in archaea.243
• Membrane Lipids: Bacterial membranes consist of fatty acids linked to glycerol by ester bonds. In contrast, archaeal membranes feature branched isoprenoids linked to glycerol by ether bonds.24
• Protein Synthesis and Transcription: Archaea share more similarities with eukaryotes than with bacteria in these processes. For instance, archaeal RNA polymerase is more complex than the bacterial version, and archaea use an initiator tRNA with unmodified methionine, unlike the modified methionine found in bacteria.2
• Metabolism: While both domains exhibit diverse metabolic strategies, methanogenesis is a unique metabolic process found exclusively within the domain Archaea.2

Additionally, while many archaea are extremophiles capable of thriving in harsh conditions like high heat or acidity, they are also found in diverse, moderate environments.23