Select the correct statement about bacteria.

A. All organisms with cells containing a membrane-enclosed nucleus and organelles are eukaryotes, whereas all organisms with cells lacking a membrane-enclosed nucleus and organelles are bacteria.
B. The majority of bacteria cause human disease.
C. Certain bacteria live within rocks kilometers below the Earth’s surface.

Bacteria are microscopic, usually single-celled living organisms that can be found in many environments. The live in practically anywhere on the planet because they are able to adapt to environmental changes. Bacteria regulate changes or modifications to their cell envelope in a coordinated way, allowing them to survive in different environments.

The main difference between bacteria and other cells is that bacteria are cells that do not contain a nucleus or other membrane-bound organelles.

These organisms can live in soil, the ocean and also inside the human gut. They can be dangerous, for example, when they cause infections they are able to injure different cells and tissues and compromise the immune system. On the other hand, most of the time they are beneficial, as in the process of fermentation such as in wine or yougurt, or helping with the digestion.