![]() ![]() Pseudomonas aeruginosa ATCC 10145-liquefaction (Gelatin Liquefaction test positive).Gelatin Liquefaction test Negative: at the end of the refrigeration period, the control tube and the test tube will be resolidified, even at the top of the tube as shown above figure. Note: Some organisms only partially liquefy gelatin or liquefy just at the surface of the tube. Gelatin Liquefaction test Positive: at the end of the refrigeration period, the control tube will be resolidified and the test tube will remain liquid at least to the depth of the stab. Result Interpretation for Gelatin Liquefaction Test Reincubate a negative test for up to 2 weeks if indicated by the nature of the organism, and examined at regular intervals.Gently invert to detect liquefaction by the test organism after 30 min of refrigeration. Do not shake or invert the tubes prior to refrigeration. Gently remove the inoculated and uninoculated tubes from the incubator and refrigerate for at least 30 min or until the control tube solidifies.Incubate the test and an uninoculated control tube for 48 hours.After touching several well-isolated colonies with a sterile needle, stab directly down the center of the tube to approximately 10 mm from the bottom. The medium should be solidified at room temperature. Incubation temperatures vary according to the nature of organisms e.g for Enterobacteriaceae and fluorescent Pseudomonas 22☌ and for non-fermenting, gram-negative rods 30☌.Negative Control : Escherichia coli ATCC 25922 Procedure of G elatin Liquefaction Test Positive Control: Pseudomonas aeruginosa ATCC 10145 Test organism ( pure or well-isolated colonies, 18-24 hours old culture).Requirement for Gelatin Liquefaction Test This enzyme destroys the structure of the gelatin, and it becomes liquid. Gelatinase is a proteolytic enzyme that hydrolyzes gelatin into polypeptides and individual amino acids. It is a protein derived from the animal protein collagen– a component of vertebrate connective tissue. It is nowadays replaced by agar due to having better-solidifying properties than gelatin but even in use for gelatin liquefaction test to identify various organisms like Bacillus, Clostridium, Proteus, Pseudomonas, and Serratia. Gelatin is a solidifying agent and is used in microbiology for culture media before the use of agar. The bottom test tube shows a gelatin medium after chilling that has a semi-solid state indicating that gelatin hydrolysis did not occur (gelatin hydrolysis negative).Introduction of Gelatin Liquefaction Test The top test tube shows a gelatin medium after chilling that has a more liquid form indicating that gelatin hydrolysis occurred (gelatin hydrolysis positive). Those species that do not hydrolyze gelatin will not have an effect on the gelatin and it will maintain its semi-solid state after chilling.įigure 1: Results from two gelatin hydrolysis tests. After incubation of the bacteria in the medium that hydrolyze gelatin, the medium will no longer form a semi-solid state, even after chilling. When bacteria that have this enzyme are inoculated into a nutrient medium containing gelatin, they will produce a gelatinase enzyme and break down the gelatin. To determine if a bacterial species hydrolyzes gelatin (and therefore has the a gelatinase gene and produces a gelatinase enzyme), the gelatin hydrolysis test is used. As such, the gelatin hydrolysis test is used to differentiate between bacteria that do and do not hydrolyze gelatin, and therefore is useful for characterizing and identifying bacterial species. Only those species of bacteria that do have a gelatinase gene are capable of producing a gelatinase and are capable of breaking down gelatin and using it as a nutrient source. Not all species of bacteria have a gene for a gelatinase enzyme. Therefore, it must first be broken down ( gelatin hydrolysis) by exoenzyme proteins called gelatinases. Gelatin provides a rich source of amino acids and peptides for bacteria, but its structure is too large to be transported inside the cell directly. When chilled on ice, gelatin forms cross-links to itself to create a semi-solid state (gelatin makes Jello! have its unique form and texture). Gelatin is a protein derived from collagen, a connective tissue of animals. ![]()
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