Page 32 - MNUmicrobiology practical 2025

General Microbiology & Immunology (PM 401) second level Semester 4 2024/2025

1. Coccus

• A coccus is singular; cocci is plural

• A coccus-shaped bacterium is usually spherical, although some appear oval,

elongated, or flattened on one side.

• Based on their planes of division and tendency to remain attached after replication,

cocci may be seen in one of the following arrangements:

A- Division in one plane produces
1- Diplococcus: a
pair of cocci

Neisseria
2- Streptococcus: a
chain of cocci

Streptococcus pyogenes

B- Division in two planes
• Tetrad: a square
of 4 cocci

Micrococcus luteus

General Microbiology & Immunology (PM 401) Practical note Page 21