Aerobic organism

Aerobic and anaerobic bacteria can be identified by growing them in test tubes of thioglycollate broth:
1: Obligate aerobes need oxygen because they cannot ferment or respire anaerobically. They gather at the top of the tube where the oxygen concentration is highest.
2: Obligate anaerobes are poisoned by oxygen, so they gather at the bottom of the tube where the oxygen concentration is lowest.
3: Facultative anaerobes can grow with or without oxygen because they can metabolise energy aerobically or anaerobically. They gather mostly at the top because aerobic respiration generates more ATP than either fermentation or anaerobic respiration.
4: Microaerophiles need oxygen because they cannot ferment or respire anaerobically. However, they are poisoned by high concentrations of oxygen. They gather in the upper part of the test tube but not the very top.
5: Aerotolerant organisms do not require oxygen as they metabolise energy anaerobically. Unlike obligate anaerobes however, they are not poisoned by oxygen. They can be found evenly spread throughout the test tube.

An aerobic organism or aerobe is an organism that can survive and grow in an oxygenated environment.

Types

• Obligate aerobes need oxygen to grow. In a process known as cellular respiration, these organisms use oxygen to oxidize substrates (for example sugars and fats) and generate energy.
• Facultative anaerobes use oxygen if it is available, but also have anaerobic methods of energy production.
• Microaerophiles require oxygen for energy production, but are harmed by atmospheric concentrations of oxygen (21% O₂).
• Aerotolerant anaerobes do not use oxygen but are not harmed by it.

Glucose

A good example would be the oxidation of glucose (a monosaccharide) in aerobic respiration.

C₆H₁₂O₆ + 6 O₂ + 38 ADP + 38 phosphate → 6 CO₂ + 6 H₂O + 38 ATP

Oxygen is used during the oxidation of glucose and water is produced.

This equation is a summary of what actually happens in three series of biochemical reactions: glycolysis, the Krebs cycle, and oxidative phosphorylation.

See also

• Aerobic digestion
• Anaerobic digestion
• Facultative anaerobic organism
• Fermentation (biochemistry)
• Microaerophile
• Obligate anaerobe