Prokaryotes are single-celled organisms that have a simple cell structure without compartmentalisation (they do not possess any membrane-bound organelles)

• Prokaryotic cells can have a number of different shapes: rods (bacilli), spheres (cocci), spirals (spirilla), commas (vibrio) or corkscrews (spirochetes)

Prokaryotes have been classified into two different domains, based on key differences in structure and genetics

• Bacteria: A large and diverse range of organisms including many pathogenic (disease-causing) forms

• Archaea: Include a variety of extremophiles (organisms living in extreme environments), but also exist in normal habitats

Prokaryotic Cell Structure

All prokaryotic cells share a number of key cellular components:

• The genetic material is found within a region of the cytosol called the nucleoid (the single DNA strand is called the genophore)

• Prokaryotes may contain additional DNA molecules (plasmids) that can be exchanged via bacterial conjugation (horizontal gene transfer)

• The ribosomes within the cell that are responsible for protein synthesis are characteristically small in size (70S)

• Prokaryotic cells all possess a cell wall and may possess an additional outer covering (a slime capsule called a glycocalyx)

• They may possess hair-like extensions called pili, that aid in adhesion (attachment pili) or plasmid exchange (sex pili)
  

• Additionally, many prokaryotes may possess several whip-like projections called flagella, which facilitate movement
  

Bacterial Cell Structure (Bacillus)