Lysine Iron Agar (LIA) Slants
Lysine iron agar (LIA) slants test organisms for the ability to deaminate lysine or decarboxylate lysine. Lysine deamination is an aerobic process which occurs on the slant of the media. Lysine decarboxylation is an anaerobic process which occurs in the butt of the media.
LIA slants contain lysine, glucose, peptones, bromcresol purple (pH indicator), sodium thiosulfate and ferric ammonium citrate. If the organism has the ability to decarboxylate lysine, it produces an amine end-product which reacts with the pH indicator to give a purple color in the butt of the tube. (Negative decarboxylation: yellow butt).
If the organism has the ability to deaminate lysine, the ammonia produced will react with the ferric ammonium citrate to produce a dark red color on the slant of the tube. (Negative deamination: purple slant). Organisms which produce hydrogen sulfide gas will exhibit a black precipitate in the butt of the tube.
Tube 1: Positive decarboxylation (butt), negative deamination (slant)
Tube 2: Negative decarboxylation (butt), positive deamination (slant)