<p>Aerobically different bacteria behave differently when grown in liquid culture:
</p>
<ol><li>Obligate aerobic bacteria gather at the top of the test tube in order to absorb maximal amount of oxygen.</li>
<li>Obligate anaerobic bacteria gather at the bottom to avoid oxygen.</li>
<li>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.</li>
<li>Microaerophiles gather at the upper part of the test tube but not at the top. They require oxygen, but at a lower concentration.</li>
<li>Aerotolerant bacteria are not affected at all by oxygen, and they are evenly spread along the test tube.</li></ol>
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