1. Bacteria:
- Eubacteria:
- Cyanobacteria (blue-green algae)
- Gram-positive bacteria (e.g., Lactobacillus, Staphylococcus)
- Gram-negative bacteria (e.g., Escherichia coli, Pseudomonas)
- Archaebacteria:
- Methanogens: produce methane gas (e.g., Methanogenium)
- Extreme halophiles: inhabit highly saline environments (e.g., Halobacterium)
- Extreme thermophiles: live in extremely hot environments (e.g., Pyrococcus)
- Acidophiles: grow in highly acidic conditions (e.g., Acidithiobacillus)
2. Cyanobacteria (blue-green algae):
- Photoautotrophic prokaryotes
- Perform oxygenic photosynthesis
- Found in both freshwater and marine environments
- Some species can fix atmospheric nitrogen