Rucete ✏ Biology In a Nutshell
1. Characteristics of Bacteria
- Prokaryotic cells: No nucleus or membrane-bound organelles
- Cell walls contain peptidoglycan (unlike archaea)
- DNA is not associated with histone proteins
- Sensitive to antibiotics like streptomycin and chloramphenicol
- Reproduce asexually by binary fission
2. Shapes of Bacteria
- Cocci: spherical
- Bacilli: rod-shaped
- Spirilla: spiral-shaped
3. Movement
- Some bacteria use flagella for movement
- Others may glide or exhibit twitching motion
4. Types of Bacteria
a) Cyanobacteria (Blue-green algae)
- Photosynthetic autotrophs that use chlorophyll a
- Contain accessory pigments called phycobilins
- Have heterocysts—specialized cells for nitrogen fixation
b) Chemosynthetic Bacteria
- Autotrophs that obtain energy by oxidizing inorganic substances
- Include nitrifying bacteria that convert ammonia (NH₃) to nitrites (NO₂⁻) and then to nitrates (NO₃⁻)
c) Nitrogen-Fixing Bacteria
- Convert atmospheric nitrogen (N₂) into ammonia (NH₃)
- Often live in mutualistic relationships with plants (e.g., root nodules of legumes)
d) Spirochetes
- Spiral-shaped bacteria that move using a corkscrew motion
- Some are free-living, others are pathogenic (e.g., Lyme disease)
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Biology in a nutshell