What is the characteristic feature of obligate anaerobes?

Obligate anaerobes are organisms that are unable to survive in the presence of oxygen. This is primarily due to their lack of the necessary enzymes, such as catalase or superoxide dismutase, that neutralize the harmful effects of reactive oxygen species which can form in aerobic environments. When exposed to oxygen, obligate anaerobes experience oxidative stress, leading to cellular damage and ultimately death. This adaptation allows them to thrive exclusively in oxygen-free environments, such as certain soil layers, deep aquatic systems, or within the intestines of animals, where they play vital roles in various biochemical processes, such as fermentation. Understanding the environment in which obligate anaerobes exist helps illuminate their unique metabolic pathways and ecological contributions.