In which organisms are prokaryotic cells found? Give information about the diversity of their shapes.

(N/A) $\Rightarrow$ Prokaryotic cells are found in bacteria,blue-green algae,mycoplasma,and $PPLO$ (Pleuro Pneumonia-Like Organisms).
$\Rightarrow$ They are generally smaller and multiply more rapidly than eukaryotic cells.
$\Rightarrow$ They vary greatly in shape and size. The four basic shapes of bacteria are:
$(i)$ Bacillus (rod-like)
$(ii)$ Coccus (spherical)
$(iii)$ Vibrio (comma-shaped)
$(iv)$ Spirillum (spiral)
$\Rightarrow$ Despite their diversity in shape and function,the fundamental organization of the prokaryotic cell remains consistent.
$\Rightarrow$ All prokaryotes have a cell wall surrounding the cell membrane (except in mycoplasma).
$\Rightarrow$ The fluid matrix filling the cell is the cytoplasm.
$\Rightarrow$ There is no well-defined nucleus. The genetic material is naked and not enveloped by a nuclear membrane.
$\Rightarrow$ Many bacteria have small circular $DNA$ outside the genomic $DNA$,called plasmids. These confer unique phenotypic characters like antibiotic resistance.