Bacteria – Class 11 | Chapter – 2 | Short Notes Series PDF
Bacteria are the sole members of the Kingdom Monera. They are the most abundant micro-organisms. Bacteria occur almost everywhere. Hundreds of bacteria are present in a handful of soil. They also live in extreme habitats such as hot springs, deserts, snow and deep oceans where very few other life forms can survive. Many of them live in or on other organisms as parasites.
Bacteria Diagram
The bacteria diagram given below represents the structure of a typical bacterial cell with its different parts.
Classification of Bacteria
Bacteria can be classified into various categories based on their features and characteristics. The classification of bacteria is mainly based on the following:
- Shape
- Composition of the cell wall
- Mode of respiration
- Mode of nutrition
Classification of bacteria based on Shape
| Type of Classification | Examples |
| Bacillus (Rod-shaped) | Escherichia coli (E. coli) |
| Spirilla or spirochete (Spiral) | Spirillum volutans |
| Coccus (Sphere) | Streptococcus pneumoniae |
| Vibrio (Comma-shaped) | Vibrio cholerae |
Classification of bacteria based on the Composition of the Cell Wall
| Type of Classification | Examples |
| Peptidoglycan cell wall | Gram-positive bacteria |
| Lipopolysaccharide cell wall | Gram-negative bacteria |
Classification of bacteria based on the Mode of Nutrition
| Type of Classification | Examples |
| Autotrophic Bacteria | Cyanobacteria |
| Heterotrophic Bacteria | All disease-causing bacteria |
Classification of bacteria based on the Mode of Respiration
| Type of Classification | Examples |
| Anaerobic Bacteria | Actinomyces |
| Aerobic Bacteria | Mycobacterium |
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