What term describes bacteria that grow in the absence of free oxygen?

The term that describes bacteria that grow in the absence of free oxygen is indeed anaerobes. Anaerobes can be further classified into different categories based on their oxygen tolerance; for instance, obligate anaerobes require an oxygen-free environment to survive, as oxygen can be toxic to them. This adaptation allows them to thrive in environments such as deep soils, sludge, and the gastrointestinal tract of animals, where oxygen is limited or nonexistent.

Understanding the role of anaerobes is crucial in bacteriology, particularly when considering infections or industrial processes that involve these organisms. Knowing that certain bacteria do not require oxygen to grow can help in the identification and treatment of infections caused by anaerobic bacteria.

The other terms, while related to the presence of oxygen, refer to different types of bacteria. Aerobes require oxygen for growth, capnophiles thrive in environments with high carbon dioxide levels, and aerotolerant bacteria can survive in the presence of oxygen but do not use it for growth, highlighting the diversity of bacterial adaptation to varying environmental conditions.