In five kingdom system, the main basis of classification:
1. Structure of the nucleus
2. Nutrition
3. Structure of cell wall
4. Asexual reproduction
Barophilic prokaryotes:
| 1. | Grow slowly in highly alkaline frozen lakes at high altitudes |
| 2. | Grow and multiply in very deep marine sediments |
| 3. | Readily grow and divide in seawater enriched in any soluble salt of barium |
| 4. | Occur in water containing high concentrations of barium hydroxide |