Bacteria have many different metabolic patterns. Some bacteria only need carbon dioxide as a carbon source and are called autotrophs. Those who get energy from light through photosynthesis are called photosynthetic autotrophs. Those who rely on oxidized compounds for energy are called chemoautotrophs. Other bacteria rely on organic carbon as carbon source, which is called heterotrophic bacteria.
Photosynthetic autotrophic bacteria include cyanobacteria, which are the oldest known organisms and may play an important role in producing oxygen in the earth's atmosphere. Other photosynthetic bacteria carry out some processes that do not produce oxygen. Include green sulfur bacteria, green non-sulfur bacteria, purple sulfur bacteria, purple non-sulfur bacteria and Heliobacter.
Nutrients required for normal growth include nitrogen, sulfur, phosphorus, vitamins and metal elements such as sodium, potassium, calcium, magnesium, iron, zinc and cobalt.
According to their reaction to oxygen, most bacteria can be divided into the following three categories: some can only grow under aerobic conditions, called aerobic bacteria; Others can only grow under anaerobic conditions, called anaerobic bacteria; Some facultative anaerobic bacteria can grow under aerobic or anaerobic conditions. Bacteria can also thrive in what humans consider extreme environments. This creature is called an extremophile. Some bacteria exist in hot springs and are called thermophilic bacteria; Others live in high salt lakes and are called halophilic microorganisms; Other bacteria exist in acidic or alkaline environment and are called acidophilic bacteria and alkalophilic bacteria. Others exist in alpine glaciers and are called psychrophilic bacteria.