Almost all known physiological types of microorganisms inhabitating marine and fresh water habitats are also found in subsurface habitats.
Different physiological .groups detected in subsurface habitats are: manganese solubilizers, sulfate reducers, nitrate reducers, denitrifiers, iron reducing bacteria, methanogens, acetogens, coliforms, faecal streptococci and other metabolically active microorganisms.
This physiological diversity of subsurface microorganisms explains their potential role in biogeochemical cycling.
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