Name the two kingdoms of bacteria and explain why scientists classify them separately?

The two kingdoms of bacteria are eubacteria and archaebacteria.
Eubacteria are what people are most familiar with, living in ordinary environments.
Archaebacteria, on the other hand, are known for living in extreme environments, such as the depths of the ocean, in volcanoes and geysers, etc. They are specially adapted to live in these environments with such high pH levels, salt levels, or whatever else is abnormal to a normal environment.