Drop a germ into a tube of thioglycollate broth and oxygen sorts it out for you. Oxygen soaks in at the top and is used up on the way down, so the tube is a ladder of oxygen levels. Pick a group, set the tube, and run the clock. Where the cloudiness lands is the answer.
Obligate aerobe
Five ways to meet oxygenpick a group and run the clock
The group
Hours in the incubator at 37°C
0 h, just inoculated24 h48 h
What has been done to the tube
Why oxygen can kill: using oxygen makes two poisons on the side, superoxide and hydrogen peroxide. Two enzymes clean them up. Superoxide dismutase handles superoxide and catalase handles peroxide. A germ with neither one is wrecked by air.