Lab #10 Fermentation and #11 IMViC

What color change indicates acid production in phenol red broth?

Red to yellow

What does a bubble in the Durham tube indicate?

Gas production

Why must fermentation results be read within 48 hours?

Delayed reading may result in false negatives from alkaline byproducts

Which sugar is typically fermented first and why?

Glucose, because it's a simple monosaccharide and easy to metabolize

What does a red layer after adding Kovac’s reagent indicate?

Positive indole test – bacteria has tryptophanase

What does the Methyl Red test detect?

Use of mixed acid fermentation pathway; red means acidic

What does VP test detect?

Acetoin production from butylene glycol fermentation; red = positive

What does blue color in citrate slant indicate?

Positive result; citrate is used as sole carbon source and alkaline product

Why is IMViC medically important?

Identifies gram negative rods that indicate fecal contamination.