University of Michigan - Ann Arbor

Bacteria can be classified based on their different morphologies.
- Coccus
- Bacillus
- Vibrio
- Coccobacillus
- Spirillum
- Spirochete

Cell Morphologies

These bacterial cells lack a cell wall, thus they do not have a stable shape. They may appear as round bodies or interlacing filaments. 

Coccus bacteria are round and spherical in shape.

Bacterial cells that are rod shaped are bacilli. Bacilli are capable of forming endospores. 

These bacterial cells are curved rod shaped. 

Coccobacilli bacteria are short rod shaped bacteria. 

Spirilla are rigidly spiraled shaped bacterial cells.

Spirochete cells are longer and helical spiral bacterial cells. They are members of the Spirochaetota phylum of bacteria.

Pathogenic bacteria are bacteria that can cause infectious disease.