Oxygen Requirements Are A Defining Factor
- The ability of an organism to survive with or without oxygen depends on its metabolic pathways and adaptations.
- Organisms can be grouped into three categories based on their oxygen tolerance:
- Obligate Aerobes: Organisms that require oxygen to survive.
- Obligate Anaerobes: Organisms that cannot tolerate oxygen and thrive in its absence.
- Facultative Anaerobes: Organisms that can survive with or without oxygen.
Obligate Aerobes Thrive in Oxygen-Rich Environments
Definition
Obligate aerobes
Obligate aerobes are organisms that depend on oxygen for aerobic respiration, a process that efficiently generates ATP (energy) by breaking down glucose.
- Without oxygen, these organisms cannot survive because they lack alternative pathways to produce sufficient energy.
Characteristics of Obligate Aerobes
- Oxygen Requirement: A continuous supply of oxygen is essential.
- Habitat: Found in oxygen-rich environments such as forests, the upper layers of soil, and aquatic surfaces.
- Plants and Animals: Humans, birds, and mammals.
- Certain Bacteria: Micrococcus luteus, which lives on human skin., which lives on human skin.
Students often confuse obligate aerobes with facultative anaerobes, mistakenly thinking all organisms can switch between aerobic and anaerobic respiration. Remember, obligate aerobes must have oxygen to survive.
Obligate Anaerobes See Oxygen as a Threat
Definition
Obligate Anaerobes
Obligate anaerobes find oxygen toxic. These organisms thrive in anoxic (oxygen-free) environments, such as deep ocean sediments, swamps, or the guts of animals.
- Oxygen damages their cells because they lack enzymes like catalase and superoxide dismutase, which neutralize harmful reactive oxygen species.
Characteristics of Obligate Anaerobes
- Oxygen Tolerance: Cannot survive in the presence of oxygen.
