<P> Unlike eukaryotes, the bacterial DNA is not enclosed inside of a membrane - bound nucleus but instead resides inside the bacterial cytoplasm . This means that the transfer of cellular information through the processes of translation, transcription and DNA replication all occur within the same compartment and can interact with other cytoplasmic structures, most notably ribosomes . The bacterial DNA is not packaged using histones to form chromatin as in eukaryotes but instead exists as a highly compact supercoiled structure, the precise nature of which remains unclear . Most bacterial DNA are circular although some examples of linear DNA exist (e.g. Borrelia burgdorferi). Along with chromosomal DNA, most bacteria also contain small independent pieces of DNA called plasmids that often encode for traits that are advantageous but not essential to their bacterial host . Plasmids can be easily gained or lost by a bacterium and can be transferred between bacteria as a form of horizontal gene transfer . So plasmids can be described as an extra chromosomal DNA in a bacterial cell . </P> <P> In most bacteria the most numerous intracellular structure is the ribosome, the site of protein synthesis in all living organisms . All prokaryotes have 70S (where S = Svedberg units) ribosomes while eukaryotes contain larger 80S ribosomes in their cytosol . The 70S ribosome is made up of a 50S and 30S subunits . The 50S subunit contains the 23S and 5S rRNA while the 30S subunit contains the 16S rRNA . These rRNA molecules differ in size in eukaryotes and are complexed with a large number of ribosomal proteins, the number and type of which can vary slightly between organisms . While the ribosome is the most commonly observed intracellular multiprotein complex in bacteria other large complexes do occur and can sometimes be seen using microscopy . </P> <P> While not typical of all bacteria some microbes contain intracellular membranes in addition to (or as extensions of) their cytoplasmic membranes . An early idea was that bacteria might contain membrane folds termed mesosomes, but these were later shown to be artifacts produced by the chemicals used to prepare the cells for electron microscopy . Examples of bacteria containing intracellular membranes are phototrophs, nitrifying bacteria and methane - oxidising bacteria . Intracellular membranes are also found in bacteria belonging to the poorly studied Planctomycetes group, although these membranes more closely resemble organellar membranes in eukaryotes and are currently of unknown function . Chromatophores are intracellular membranes found in phototrophic bacteria . Used primarily for photosynthesis, they contain bacteriochlorophyll pigments and carotenoids . </P> <P> The prokaryotic cytoskeleton is the collective name for all structural filaments in prokaryotes . It was once thought that prokaryotic cells did not possess cytoskeletons, but recent advances in visualization technology and structure determination have shown that filaments indeed exist in these cells . In fact, homologues for all major cytoskeletal proteins in eukaryotes have been found in prokaryotes . Cytoskeletal elements play essential roles in cell division, protection, shape determination, and polarity determination in various prokaryotes . </P>

Draw the structure of a typical bacterial cell