Prokaryotic

Prokaryotes are a group of organisms that lack a cell nucleus (nucleus), or any other membrane-bound organelles. They differ from the eukaryotes, which have a cell nucleus. Most are unicellular, but some prokaryotes are multicellular.

The word prokaryote comes from the Greek πρό (pro) "before" and κάρυον (karyon) "nut or kernel". Prokaryotes can be divided into two domains, Archaea and Bacteria. In contrast, species with nuclei and organelles are placed in the third domain, Eukaryota.

Characteristics

Prokaryotes have a prokaryotic cytoskeleton that is more primitive than that of the eukaryotes. Besides homologues of actin and tubulin (MreB and FtsZ), the helically arranged building-block of the flagellum, flagellin, is one of the most significant cytoskeletal proteins of bacteria, as it provides structural backgrounds of chemotaxis, the basic cell physiological response of bacteria.

Genetic Diversity

Prokaryotes have a high genetic diversity that is not immediately apparent from morphological observation. The nucleoid consists of a long, continuous, circular thread of double-stranded DNA, (most commonly) of multiple copies.

Reproduction

Prokaryotes reproduce without fusion of gametes (gametes). The offspring cell is a clone of the parent cell, i.e., they have the same genetic material.

Ecology

Prokaryotes have diversified greatly throughout their long existence. The metabolism of prokaryotes is far more varied than that of eukaryotes, leading to many highly distinct prokaryotic types.

See also

• Cell biology
• Microbiology
• Origin of life
• Timeline of evolution

Prokaryotic Resources
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