Anaerobic

Aerobically different bacteria behave differently when grown in liquid culture:

1. Obligate aerobic bacteria gather at the top of the test tube in order to absorb maximal amount of oxygen.
2. Obligate anaerobic bacteria gather at the bottom to avoid oxygen.
3. Facultative bacteria gather mostly at the top, since aerobic respiration is advantageous (ie, energetically favorable); but as lack of oxygen does not hurt them, they can be found all along the test tube.
4. Microaerophiles gather at the upper part of the test tube but not at the top. They require oxygen, but at a lower concentration.
5. Aerotolerant bacteria are not affected at all by oxygen, and they are evenly spread along the test tube.