Shape of Bacteria

Shape of Bacteria

Depending on their shape, bacteria are classified into several types (Fig. 2-6):

Cocci: The cocci (kokkos, berry) are oval or spherical cells.These may be arranged in pairs (e.g., pneumococci, menin-gococci, and gonococci), tetrads (micrococci), chains (e.g., streptococci), and clusters (e.g., staphylococci).

Bacilli: The bacilli (bacillus,rod) are rod shaped. These bacillimay show either of the following arrangement:

1.     Coccobacilli: Length of the bacteria is approximately the sameas its width, e.g., Brucella.

2.     Streptobacilli: These are arranged in chains, e.g.,Streptobacillus.

3.     Comma shaped: They exhibit curved appearance, e.g., Vibrio.

4.     Spirilla: They exhibit rigid spiral forms, e.g.,Spirillum.

Spirochetes: Spirochetes (spira,coil;chaite,hair) are slender,flexuous spiral forms, e.g., Treponema.

Actinomycetes: Actinomycetes (actin,ray;mykes,fungus) arebranching filamentous bacteria resembling fungi. They possess a rigid cell wall.