Three Domains of Life
Three Domains of Life
Microbes are found in all three domains of life: bacteria, archaea, and eukaryotes.
Diverse species of the three domains are explored in Microbial Biorealm.
All cells on Earth resemble each other | |||
Chromosomal material |
Double-stranded DNA | ||
RNA transcription |
Common ancestral RNA polymerase | ||
Translation |
Common ancestral rRNAs and elongation factors | ||
Protein |
Common ancestral functional domains | ||
Cell structure |
Aqueous cell compartment bounded by a membrane | ||
Archaea resemble Bacteria |
|||
Cell volume |
1 to 100 μm2 (usually) |
1 to 106 μm2 | |
DNA chromosome |
Circular (usually) |
Linear | |
Gene organization |
Multi-gene operons; few introns |
Single genes; | |
Metabolism |
Denitrification, N2 fixation, lithotrophy, respiration and fermentation |
Respiration and fermentation | |
Nuclear membrane |
None (nucleoid) |
Nuclear membrane | |
Multicellularity |
Simple |
Complex | |
Archaea resemble Eukaryotes | |||
Monomolecular cell wall |
Peptidoglycan |
Absent in most species | |
Ribosome sensitivity to |
Sensitive |
Resistant | |
Translation initiator |
Formyl-Met |
Methionine (except mitochondrial F-Met) | |
RNA polymerase |
Bacterial |
Eukaryotic | |
Transcription factors |
Bacterial |
Eukaryotic | |
Archaea Differ from Bacteria and Eukaryotes | |||
Methanogenesis |
No |
Yes |
No |
Highest temperature growth |
> 90ºC |
> 110ºC |
> 60ºC |
Photosynthesis |
Many species. |
Halobacteria only; |
Many species; bacterial origin. |
Chlorophyll light absorption |
Red and blue |
Green |
Red and blue |
Membrane lipids (major) |
Ester-linked |
Ether-linked isoprenoids |
Ester-linked |
Pathogens that infect |
Many pathogens |
No pathogens |
Many pathogens |