National Board Dental Hygiene Examination (NBDHE) Dental Hygienist Practice Test

Which type of microbe cannot perform or may be destroyed in the presence of oxygen?

1. Aerobes

2. Facultative anaerobes

3. Microaerophiles

4. Anaerobes

The correct answer is: Anaerobes

Anaerobes are microbes that cannot perform or may be destroyed in the presence of oxygen. These organisms thrive in environments devoid of oxygen and often rely on anaerobic respiration or fermentation processes for energy production. Oxygen can be toxic to anaerobes because they lack the necessary enzymes, such as superoxide dismutase and catalase, to neutralize reactive oxygen species that are generated in aerobic conditions. This sensitivity can lead to cell death or inhibited growth when exposed to oxygen. In contrast, aerobes utilize oxygen for their metabolic processes, while facultative anaerobes can switch between aerobic and anaerobic metabolism depending on the availability of oxygen. Microaerophiles require reduced levels of oxygen for their survival but are still capable of using it in their metabolic processes, indicating that they are not adversely affected by low oxygen concentrations.