The Cells That Breathe Two Ways | Quanta Magazine:
Then the team added oxygen back into the mix. As expected, the bacteria grew faster. But, to the researchers’ surprise, RSW1 also still produced hydrogen sulfide gas, as if it were anaerobically respiring. In fact, the bacteria seemed to be breathing both aerobically and anaerobically at once, and benefiting from the energy of both processes. This double respiration went further than the earlier reports: The cell wasn’t just producing sulfide in the presence of oxygen but was also performing both conflicting processes at the same time. Bacteria simply shouldn’t be able to do that.