No nuclear envelope Present with nuclear envelope and nucleolus Membrane-bound organelles Absent Present. No true mitotic apparatus. There is a great range in size between prokaryotic and eukaryotic cells. Cells are often motile. Cells tend to be rigid and fairly inflexible.
Spirilla are often motile by means of flagella.
Spirochetes are also spiral shaped but are more flexible than spirilla and move by an internal flagellum known as an axial filament. A full description of a microbe should include the arrangement and grouping of the cells. As certain bacteria divide the cells can remain attached to each other. Cocci tend to display more variations in grouping than bacilli as cocci can divide along more than one axis. Bacilli only divide along their short axis.