All enterics are facultative anaerobes; they have both respiratory and fermentative enzymes. What color results would you expect for organisms of O-F glucose media inoculated with an enteric? Remember to describe both the sealed and unsealed tubes.

Enterics would be yellow in both tubes. Unsealed, yellow = oxidation. Sealed, yellow = fermentation.

The O-F glucose test (oxidative-fermentation) is used to determine whether an organism is performs oxidative or fermentative metabolism.

Oxidative metabolism (i. e respiration) takes place in the presence of oxygen while fermentative takes place in the absence of oxygen.

Facultative anaerobes can carry out both fermentation and respiration.

The O-F medium has glucose, peptones and a pH indicator. When the pH of the medium is acidic, that is glucose has been broken down, the medium turns yellow. When it is basic, it turns blue implying that peptone and not glucose had been broken down.

The sealed tube is overlaid with oil so as to prevent oxygen from getting in, making it anaerobic.

The unsealed tube allows oxygen.

Enterics would be yellow is both tubes because they are facultative anaerobes and can grow in the presence or absence of oxygen, hence they carry out both respiration and fermentation.