Prokaryotes are divided into two main domains: Bacteria and Archaea. This division is based on significant differences in their genetic, biochemical, and physiological characteristics.
Firstly, one of the key distinctions lies in their genetic material. Although both domains are prokaryotic and lack a nucleus, the structure of their genomes differs. Bacteria typically have a single, circular chromosome, while Archaea also have circular chromosomes but possess unique genes and protein synthesis machinery that are more closely related to eukaryotes.
Secondly, the composition of their cell walls varies. Bacteria usually have cell walls made of peptidoglycan, which gives them structural strength. In contrast, Archaea have cell walls composed of different materials, such as pseudopeptidoglycan or proteins, allowing them to thrive in extreme environments.
Furthermore, their metabolic pathways differ. For example, some Archaea are extremophiles, meaning they can live in extreme conditions like high salinity or temperature, habitats where most Bacteria cannot survive. The differences in metabolism also extend to their energy sources and how they metabolize nutrients.
These variations are so profound that they justify the separation of prokaryotes into two distinct domains. This classification helps scientists understand evolutionary relationships and the diverse roles prokaryotes play in ecosystems.