Microbiology

Classifications of Bacteria

Bacteria are the smallest cellular organisms and are prokaryotes. They can be identified in three ways, judging their shape, whether they are gram-positive or negative and the way they move.

Shape

Cocci
- Sphere Shaped

Bacillus
- Rod Shaped

Spirillum
- Spiral Shaped

Gram Staining

There are also differences other than shape, these include whether the bacteria is gram-positive or gram-negative. Gram-positive bacteria turn violet in colour when gram stained, whereas gram-negative bacteria absorb the red counter-stain because the size of the peptidoglycan (murein) layer. The gram-positive bacerial peptidoglycan layer is between 20 and 80 nanometers wide compared with 7 to 8 with gram-negative bacteria.

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