Technique	GELATIN LIQUEFACTION ,(/,)/,(
Principle	Gelatin hydrolysis or liquefaction is demonstrated by innoculation of a nutrient medium supplemented with gelatin. Digestion of the gelatin will allow the medium to "flow"at room temperature. Liquefaction may be apparent afte r 1-2 days (Serratia marcescens), a week (Enterobacter cloacae) or even after 2-3 months. Usually, slants are incubated below the melting point of gelatin (25 degrees C) but mesophilic microbes may grow very slowly or not at all. To overcome this difficulty, the slant may be incubated at the optimal temperature for growth and then plunged into ice water to determine whether the gelatin can still gel. An uninoculated slant of the same medium exposed for the same length of time to the same tem perature is used as a control. Gelatin medium can be mixed with agar which does not melt at 37 degrees C. After growth, the plate is flooded with acidic mercuric chloride which forms an opaque reaction with undigested gelatin while hydrolysed gelatin remains clear Thioglycollate may be added for the cultivation of Clostridia
Cautions
Method
Results
Positive control
Negative control
Reagents
Reference