Facultative anaerobes
Japanese: 通性嫌気性菌
Microorganisms that can grow with or without oxygen. They perform aerobic metabolism when oxygen is available and fermentation when it is not, flexibly adapting to their environment.
Facultative anaerobes are flexible microorganisms that can live with or without oxygen. They are neither strictly aerobic nor anaerobic—or rather, they can be either.
Yeast (Saccharomyces cerevisiae) is a prime example. With oxygen, it efficiently generates energy through respiration; without oxygen, it switches to alcoholic fermentation. This switching ability is essential in the parallel multiple fermentation of sake.
Many familiar bacteria, including E. coli and Staphylococcus, are also facultative anaerobes. They adapt their metabolism to match their environment—and this adaptability is the source of their strength. Knowing the microbial world connects to understanding fermentation.