Classification of Bacteria Based on Shape:
| Bacterial Shape |
Description |
Examples |
| Cocci |
Spherical or round-shaped bacteria. |
Streptococcus, Staphylococcus, Micrococcus |
| Bacilli |
Rod-shaped bacteria. |
Escherichia coli (E. coli), Bacillus, Clostridium |
| Spirilla |
Spiral-shaped bacteria with rigid, helical bodies. |
Spirillum, Campylobacter |
| Vibrio |
Curved or comma-shaped bacteria. |
Vibrio cholerae, Vibrio parahaemolyticus |
| Spirochetes |
Spiral-shaped bacteria with flexible, corkscrew-like bodies. |
Borrelia, Treponema, Leptospira |
Gram Staining:
| Staining Result |
Description |
Examples |
| Gram-Positive |
Retains violet stain, appears purple/blue under the microscope. |
Streptococcus, Staphylococcus, Clostridium |
| Gram-Negative |
Does not retain violet stain, appears pink/red under the microscope. |
Escherichia coli (E. coli), Pseudomonas, Salmonella |
