What is the main role of bacteria in any environment?

Bacteria are the unicellular organisms and cannot be seen with naked eye. There is no particular method of cell division, they simply divide simply by binary fission in which cell divides into two daughter cells. They do no have proper nucleus within the cell but the genetic material is attached to the cell membrane in an irregular form. They are found everywhere like top of the mountains, rivers, on land and in ice. Bacteria have the property of living in extreme weathers like extreme cold and extreme heat. They are able to live long because they become inactive for a long period of time.