Microaerophiles that grow best with a high concentration of carbon dioxide in addition to a low level of oxygen are called:
a. Aerotolerant
b. Capnophiles
c. Facultative anaerobes
d. Fastidious

Verified step by step guidance

Step 1: Understand the term 'microaerophiles' — these are organisms that require oxygen to survive, but at lower concentrations than are present in the atmosphere (usually less than 21%).

Step 2: Recognize that the question specifies microaerophiles that also require a high concentration of carbon dioxide (CO\_2) in addition to low oxygen levels.

Step 3: Review the definitions of the answer choices: (a) Aerotolerant organisms do not require oxygen but can tolerate its presence; (b) Capnophiles require elevated levels of CO\_2 for optimal growth; (c) Facultative anaerobes can grow with or without oxygen; (d) Fastidious organisms have complex nutritional requirements but this does not specifically relate to CO\_2 or oxygen levels.

Step 4: Connect the requirement for high CO\_2 concentration with the term 'capnophiles,' which are known to thrive in environments with elevated CO\_2.

Step 5: Conclude that microaerophiles needing both low oxygen and high CO\_2 are best described as capnophiles.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Microaerophiles

Microaerophiles are microorganisms that require oxygen to survive but at lower concentrations than are present in the atmosphere. They thrive in environments with reduced oxygen levels, typically around 2-10%, because higher oxygen levels can be toxic to them.

Capnophiles

Capnophiles are bacteria that grow best in environments with elevated carbon dioxide levels, often alongside low oxygen concentrations. They require increased CO2 for optimal growth, which distinguishes them from other oxygen-requiring microbes.

Oxygen Tolerance Categories of Bacteria

Bacteria are classified based on their oxygen requirements: aerotolerant bacteria tolerate oxygen but do not use it; facultative anaerobes can grow with or without oxygen; and fastidious organisms have complex nutritional needs. Understanding these categories helps identify bacterial growth preferences.

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