Lysine Iron Agar

Micro lab 2010 part 2

• Purple color indicates 6.8- (still acidic but closer to alkaline or basic

• Turns yellow when it is 5.2 or below

• Detects sulfur reduction if it turns black

• Detects pH changes that occur with fermentation

Application of the Lysine Iron Agar Procedure

Detects if there is an enzyme that cuts off a carboxyl group present (Decarboxylase) Decarboxylate sulfide (H₂S)

Detects if organism produces some sort of fermentation that reacts with lysine requires O₂ called Lysine deaminase

Used to identify members of Salmonella & Shigella

Deaminase

• Reducing amonia citrate

• Requires O₂

• Fermentation will be YELLOW

Purple on top & purple on bottom

• Lysine deaminase negative

• Lysine decarboxylase POSITIVE

Purple top

Yellow bottom

Purple indicates negative lysine deaminase

Yellow indicates positive for fermentation

Black all over precipitate

Sulfur reduction

if dicarboxylate is negative the color on the bottom is

Yellow

Fermentation means no decraboxylation

Decarboxylation positive shows as

Purple

Red is positive for what

Deaminase