Bacteria are capable of growing in a variety of environmental conditions. The oxygen
requirements for bacterial growth are a factor useful in identification. Bacteria are grouped into
several categories based on their oxygen needs. Three of these categories are:
♦ obligate aerobes that require oxygen for survival and growth
112 Bacterial Identification
♦ obligate anaerobes that do not tolerate oxygen and growth ceases in the presence of oxygen
♦ facultative anaerobes that can survive in aerobic and anaerobic conditions but prefer to grow in
the presence of oxygen.
The growth patterns of bacteria injected into a medium that limits the amount of oxygen throughout
the test tube will provide an indication of the oxygen requirements of the bacteria in question.