Cyanobacteria are classified under

Explanation

Bacteria are classified into four types based on their shape. They are
(I) Cocci :- Spherical Bacteria.
Based on the number of cells and their arrangement, the Cocci are classified into
(a) Monococcus : - A single cell
(b) Diplococcus :- A pair of cells
(c) Tetracocci : - A group of four cells
(d) Streptococcus :- A linear chain of cells
(e) Staphylococci :- A linear chain of cells
(f) Sarcina :- A group of 8 cells, arranged in cubes
(II) Bacilli :- Rod-shaped Bacteria : The Bacillus forms exist as
(a) Monobacillus :- A single rod-shaped cell.
(b) Diplobacilli :- A pair of rod - shaped cells .
(c) Streptobacilli :- A chain of rod-shaped cells.
(III) Spirillum :- Helical rod-shaped cell .
It may be a distinct helical shape (spirillum) or Slender long and cork-screw shaped (Spirochete)
(IV) Vibrio :- Comma-shaped Bacteria