| Gelatin Liquefaction |
DESCRIPTION
Gelatin cannot pass trough bacterial cell wall and thus bacteria must catabolize them into smaller components
using exocellular enzymes (gelatinase). Test detects the ability of the organism to produce enzymes which
hydrolyze gelatin.
Gelatin cannot pass trough bacterial cell wall and thus bacteria must catabolize them into smaller components
using exocellular enzymes (gelatinase). Test detects the ability of the organism to produce enzymes which
hydrolyze gelatin.
GELATIN TUBES
MEDIUM PREPARATION: add 10-15g gelatin to 100 ml nutritive broth
(heated to
55 ˚C).
Prepare a solution from one egg white (albumen) into 50 ml distilled water.
Add this solution drop by drop to 1000 ml gelatin nutritive broth (heated to
55 ˚C). Mix well then raise temperature to 115 ˚C. Albumen coagulate and
clarify the medium.
Filter trough cotton and distribute medium in tubes. Sterilize 20 minutes at
110 ˚C. Hold tubes vertically until solidification. Normally, gelatin is solid
under 20 ˚C and liquid over 28 ˚C.
PROCEDURE:
Inoculate a gelatin tube by stabbing the medium down the bottom. Incubate
at 22 ˚C, 12 days, controlling liquefaction after 1st, 10th and 12th day. If
bacteria do not grow at 22 ˚C then incubate at 37 ˚C but you need to cool
the tube by refrigeration before reading results.
MEDIUM PREPARATION: add 10-15g gelatin to 100 ml nutritive broth
(heated to
55 ˚C).
Prepare a solution from one egg white (albumen) into 50 ml distilled water.
Add this solution drop by drop to 1000 ml gelatin nutritive broth (heated to
55 ˚C). Mix well then raise temperature to 115 ˚C. Albumen coagulate and
clarify the medium.
Filter trough cotton and distribute medium in tubes. Sterilize 20 minutes at
110 ˚C. Hold tubes vertically until solidification. Normally, gelatin is solid
under 20 ˚C and liquid over 28 ˚C.
PROCEDURE:
Inoculate a gelatin tube by stabbing the medium down the bottom. Incubate
at 22 ˚C, 12 days, controlling liquefaction after 1st, 10th and 12th day. If
bacteria do not grow at 22 ˚C then incubate at 37 ˚C but you need to cool
the tube by refrigeration before reading results.
NOTES:
Liquefaction usually occurs at the surface of the medium. Viscosity of the medium increases in prolonged storage.
REFERENCES:
1. H. Raducanescu, V.Bica-Popii,1986. Bacteriologie veterinara, Ed. Ceres, Bucuresti.
2. PML Microbiologicals, Technical data sheet #370, Jan 2001.
Liquefaction usually occurs at the surface of the medium. Viscosity of the medium increases in prolonged storage.
REFERENCES:
1. H. Raducanescu, V.Bica-Popii,1986. Bacteriologie veterinara, Ed. Ceres, Bucuresti.
2. PML Microbiologicals, Technical data sheet #370, Jan 2001.
FRAZIER MEDIUM
COMPOSITION: agar 0.4%, gelatin, pH 7.2
Frazier reactive: HgCl2 15g, HCl 20 ml, distilled water 100 ml.
Pour medium in Petri dishes and disperse culture on surface. Incubate 2 to 14
days. Cover culture with 8-10 ml of Frazier reactive.
RESULTS
Non-hydrolysed gelatin forms a white, opaque precipitate. Liquefied gelatin
appears as clear area around colonies.
OTHER FORMULAS
Nutrient gelatin: pancreatic digest of gelatin 5 g, beef extract 5 g, gelatin 120
g, distilled water ad 1000 ml.
Gelatin 0.4%: gelatin 4g, distilled water ad 1000 ml.
COMPOSITION: agar 0.4%, gelatin, pH 7.2
Frazier reactive: HgCl2 15g, HCl 20 ml, distilled water 100 ml.
Pour medium in Petri dishes and disperse culture on surface. Incubate 2 to 14
days. Cover culture with 8-10 ml of Frazier reactive.
RESULTS
Non-hydrolysed gelatin forms a white, opaque precipitate. Liquefied gelatin
appears as clear area around colonies.
OTHER FORMULAS
Nutrient gelatin: pancreatic digest of gelatin 5 g, beef extract 5 g, gelatin 120
g, distilled water ad 1000 ml.
Gelatin 0.4%: gelatin 4g, distilled water ad 1000 ml.
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