aerotolerance

Aerotolerance refers to the ability of a microorganism to withstand or utilize oxygen during growth. It describes how oxygen affects survival and metabolism, spanning a spectrum from organisms that require oxygen to grow to those that are harmed by it.

Common categories are: obligate aerobes, which require oxygen; obligate anaerobes, which are inhibited or killed by oxygen; facultative anaerobes, which can grow with or without oxygen and often favor oxygen when available; aerotolerant anaerobes, which do not utilize oxygen but can tolerate its presence; and microaerophiles, which need smaller-than-atmospheric oxygen levels to grow.

Aerotolerance is determined by cellular mechanisms that manage reactive oxygen species such as superoxide and hydrogen peroxide. Many aerobically competent organisms possess enzymes like superoxide dismutase and catalase or peroxidases to detoxify ROS, enabling survival in oxygen-rich environments. In some organisms, oxygen usage is linked to energy metabolism or specific respiratory pathways, while in others oxygen is merely tolerated without serving as an electron acceptor.

In laboratory and clinical settings, aerotolerance guides culture conditions and diagnostic approaches. Growth patterns are assessed by comparing culture performance under aerobic (oxygen-present) and anaerobic (oxygen-absent) conditions, often using thioglycolate media, resazurin indicators, or anaerobic jars and microaerophilic systems. Understanding aerotolerance informs decisions in microbiology, food production, and environmental studies, affecting infection control, fermentation processes, and ecological assessments. Examples of organisms span facultative anaerobes such as many Enterobacterales and Staphylococcus species, aerotolerant anaerobes like Lactobacillus and Streptococcus, and obligate aerobes that strictly require oxygen.