The Differences among Bacteria, Archaea, and Eukaryotic Microorganisms

By Jennifer Stearns, Michael Surette

Part of Microbiology For Dummies Cheat Sheet

There are three domains of life: Bacteria (also known as Eubacteria), Archaea, and Eukarya. The Bacteria and Archaea are made up entirely of microorganisms; the Eukarya contains plants, animals, and microorganisms such as fungi and protists. The Bacteria and Archaea have been grouped together and called Prokaryotes because of their lack of a nucleus, but the Archaea are more closely related to the Eukaryotes than to the Bacteria. Here are other major differences between the three domains.

Bacteria Archaea Eukaryotes
Cell type Prokaryotic Prokaryotic Eukaryotic
Cell wall Made of peptidoglycan Does not contain peptidoglycan In plants and fungi, composed of polysaccharides
Sensitivity to antibiotics Yes No No
First amino acid during protein synthesis Formylmethionine Methionine Methionine
DNA Mostly circular chromosome and plasmids Circular chromosome and plasmids Linear chromosome, rarely plasmids
Histones No Yes Yes
Organelles No No Yes
Ribosomes 70S 70S 80S