What is the difference between a bacterium and an archaeon?
Question
The other day our teacher asked what makes bacteria different from archaea, and honestly, I wasn’t too sure. So I did some digging. Turns out, the difference isn’t just minor—it’s in their membranes, genes, metabolism, and even how they react to antibiotics. This answer helped everything click, especially how unique archaea really are.
Answer ( 1 )
Cell wall
Bacteria usually build their wall with peptidoglycan, archaeal wall lack true peptidoglycan, many use pseudo‑peptidoglycan or an S‑layer made of proteins. This difference is why lysozyme splits most bacteria but not archaea.
Membrane lipids
Bacterial phospholipids carry ester bonds linking fatty acids to glycerol‑3‑phosphate. Archaea use ether bonds on glycerol‑1‑phosphate, and many fuse the tails into a monolayer, that trick makes them tougher at high heat or salt.
Genetic machinery
The archaeal RNA polymerase, promoters and many ribosomal proteins look more eukaryotic than bacterial. As a result, rifampicin stops bacterial transcription but it barely touch most archaea.
Metabolism
Bacteria cover every style from photosynthesis to nitrification, but only archaea make methane, that pathway is unique to them. Some archaea also run modified glycolysis like the Entner‑Doudoroff variant.
Habitats
Both groups live everywhere, still archaea dominates extreme niches such as boiling springs, saturated brines and deep petroleum reservoirs. Bacteria can live there too, just not as frequently.
Taxonomy and naming
Bacteria and Archaea form two separate domains in the three‑domain tree proposed by Woese. So a bacterium and an archaeon are as distant from each other as either is from a human cell.
Quick recap
So the main things to remember is cell wall chemistry, membrane lipids, and the machinery for transcription translation. Those biochemical differences make archaeal cells act and respond different to antibiotics and stresses compared with bacteria.