Prokaryotic Cell

Eg:

• bacteria,
  
• cyanobacteria,
  
• mycoplasma (PPLO: Pleuro Pneumonia Like Organisms – discovered by Edmond Nocard)(lack a cell wall, so is pleomorphic, ie, has the ability to change shape, Without a cell wall, they are unaffected by many common antibiotics such as penicillin or other beta-lactam antibiotics that target cell wall synthesis.)
• rickettsiae (has no cell wall, so, is a pleomorphic organism too) (The majority of Rickettsia bacteria are susceptible to antibiotics of the tetracycline group.)
  Rickettsia species are carried as parasites by many ticks, fleas, and lice, and cause diseases such as typhus, rickettsialpox, Boutonneuse fever, African Tick Bite Fever, Rocky Mountain spotted fever, Australian Tick Typhus, Flinders Island Spotted Fever and Queensland Tick Typhus ^[2] in human beings.
  They have also been associated with a range of plant diseases.
  Like viruses, they only grow inside living cells

Prokaryotes are smaller than eukaryotes, and multiply more rapidly than eukaryotes.

Bacteria can be of four basic shapes

• bacillus (rod like)
  
• coccus (spherical)
  
• vibrio (comma shaped)
  
• spirillum (spiral)
  

But still the organization of all prokaryotic cells is similar.

All prokaryotes have

• cell wall surrounding cell membrane (forming the cell envelope)
  
• cytoplasm
  
• no well defined nucleus (naked genetic materials).
  Bacteria have a small circular DNA outside the genomic DNA (the single chromosome/circular DNA). These smaller DNA are called plasmids. The plasmid DNA decides phenotypic (observable) characters of the bacteria such as resistance to antibiotics. It is also used for monitoring bacterial transformation with foreign DNA.
  
• Ribosomes are the only organelles of eukaryotes that are present in prokaryotes too.
  
• Inclusions
  
• Mesosome (specialised differentiated form of cell membrane – infoldings of cell membrane)