Which type of bacteria grows only in the absence of oxygen?

The type of bacteria that grows only in the absence of oxygen is classified as anaerobes. These organisms thrive in environments where oxygen is not present and can utilize alternative metabolic pathways to generate energy. Anaerobic bacteria can be further divided into categories, such as obligate anaerobes, which cannot tolerate oxygen at all, and facultative anaerobes, which can grow in both oxygen-rich and oxygen-poor environments but prefer anaerobic conditions.

Understanding the distinctive characteristics of anaerobes is critical in microbiology, particularly in clinical settings, as they can be involved in various infections and are often found in human flora, especially in the gut. The presence of anaerobic bacteria can also significantly affect the interpretation of culture results in laboratory settings.