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Bacteria are classified several ways to help narrow down the particular organism one is looking for. Listed here are some of the primary criterion you can use to search with.

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Gram Staining and Morphology:

  • Gram Positive: stain blue-purple, have a thicker peptidoglycan layer.

  • Gram Negative:  stain red, have less peptidoglycan and more of glycolipid membrane.

Shape / Cell Structure:​

  • Cocci: spherical or oval shaped.

  • Bacilli: stick, filament, rod-like shape.

  • Spiral

Oxygen Requirement:​

  • Aerobic: require oxygen to survive.

  • Anaerobic: do not require oxygen to survive.

  • Obligate Anaerobes: survive in absence of oxygen, die when exposed to oxygen.

  • Facultative Anaerobes:  survive in absence of oxygen, can survive when exposed to oxygen.

Nutrition Requirements:​

  • Autotrophs: prepare their own food.

  • Chemoautotrophs: survive on chemicals.

  • Symbiotic: obtain food by living with other organisms.

  • Saprophytic: eat rotten material.

  • Pathogenic: responsible for diseases in humans and plants.

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