Bacteria (singular: bacterium) are classified as prokaryotes, which are single-celled organisms with a simple internal structure that lacks a nucleus and contains free-floating DNA in a twisted, thread-like mass called a nucleoid, or separate, circular pieces. called plasmids.

Bacterial cells are generally surrounded by two protective coverings: an outer cell wall and an inner cell membrane. Certain bacteria, like mycoplasmas, have no cell wall at all. Some bacteria may even have a third outer protective layer called a capsule. The whip-like extensions often cover the surfaces of bacteria, the long ones called flagella or the short ones called pili, which help the bacteria move and adhere to a host.

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Dear Student,

the typical internal structure of the bacterium is provided in the following points,

• a typical bacterium lacks a well defined nuclei and membrane-bound organelles, and with chromosomes composed of a single closed DNA circle
• They are of various different shapes and sizes, such as, minute spheres, cylinders and spiral threads, to flagellated rods, and filamentous chains.
• Structurally a bacterium consists of,
  • cytoplasmic membrane surrounded by a peptidoglycan cell wall and maybe an outer membrane
  • fluid cytoplasm containing a nuclear region (nucleoid) and numerous ribosomes
  • various external structures such as a glycocalyx, flagella, and pili.