Size, Shape, and Arrangement of Bacterial Cells Most bacteria fall within a range from 0.2 to 2.0 μm in diameter and from 2 to 8μm in length. They have a few basic shapes-spherical coccus (plural, cocci, meaning berries), rod-shaped bacillus (plural, bacilli, meaning little staffs), and spiral. Cm = 10-2 meter mm = 10-3 meter μm = 10-6 meter nm = 10-9 meter BacteriaSize, Shape, and Arrangement of Bacterial Cells Most bacteria fall within a range from 0.2 to 2.0 μm in diameter and from 2 to 8μm in length. They have a few basic shapes-spherical coccus (plural, cocci, meaning berries), rod-shaped bacillus (plural, bacilli, meaning little staffs), and spiral. Cm = 10-2 meter mm = 10-3 meter μm = 10-6 meter nm = 10-9 meter Bacteria