Oxygen Classification
| Oxygen Class | Characteristics | Examples from Lab |
| Obligate Aerobe | Require O2 as final electron acceptor Able to detoxify toxic forms of oxygen Live in atmospheric (20%) oxygen levels | Mycobacterium smegmatis, Aspergillis niger, Micrococcus luteus, Pseudomonas aeruginosa, Bacillus megaterium |
| Microaerophile | Require O2 as final electron acceptor Limited ability to detoxify toxic forms of oxygen Live in low (2-10%) oxygen levels | Saccharomyces cerevisiae* *Typically facultative, but our lab strain behaved like a microaerophile |
| Facultative | Will use O2 as final electron acceptor in aerobic environments Can use alternate electron acceptors or fermentation in anaerobic environments Able to detoxify toxic forms of oxygen Live in aerobic or anaerobic environments, but grow better aerobically | Escherichia coli, Bacillus cereus, Staphylococcus xylosus |
| Aerotolerant | Never use O2 as final electron acceptor -- metabolism is strictly anaerobic Able to detoxify toxic forms of oxygen Live in aerobic or anaerobic environments | Enterococcus faecalis |
| Obligate Anaerobe | Never use O2 as final electron acceptor -- metabolism is strictly anaerobic Unable to detoxify toxic forms of oxygen Live in anaerobic environments only. | Clostridium sporogenes |