In addition there are: Star shaped cells (genus Stella); Square flat cells (halophilic archaebacteria); Triangular cells (Haloarcula); Branching mycelium – like filaments (Streptomyces) (Fig. 4)

Genetically most bacteria are monomorphic (single shape), but some have many shapes and are called pleomorphic (Rhizobium and Corynebacterium)

Structure:

A variety of structures are found I prokaryotic cells. The cells are almost always are bounded by a chemically complex cell wall. In between the cell wall and the periplasmic space lies the plasma membrane (Fig. 5). Internal membrane bound organelles are absent in prokaryotes and hence the internal is morphologically simple. The genetic material is localized in a discrete region called nucleoid and not separated from the surrounding cytoplasm by membrane. Ribososmes and inclusions are found scattered in the cytoplasmic matrix. Bacteria use flagella for locomotion, and in addition, many cells are surrounded by a capsule or slime layer external to the cell wall.

Fig.5. Generalized structure of a bacterium