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  Section: Biotechnology Methods » Microbiology
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Gelatin Hydrolysis Test

  The Microscopy
  The Bright Field Microscope
  Introduction to the Microscope and Comparison of Sizes and Shapes of Microorganisms
  Cell Size Measurements: Ocular and Stage Micrometers
  Measuring Depth
  Measuring Area
  Cell Count by Hemocytometer or Measuring Volume
  Measurement of Cell Organelles
  Use of Darkfield Illumination
  The Phase Contrast Microscope
  The Inverted Phase Microscope
  Aseptic Technique and Transfer of Microorganisms
  Control of Microorganisms by using Physical Agents
  Control of Microorganisms by using Disinfectants and Antiseptics
  Control of Microorganisms by using Antimicrobial Chemotherapy
  Isolation of Pure Cultures from a Mixed Population
  Bacterial Staining
  Direct Stain and Indirect Stain
  Gram Stain and Capsule Stain
  Endospore Staining and Bacterial Motility
  Enumeration of Microorganisms
  Biochemical Test for Identification of Bacteria
  Triple Sugar Iron Test
  Starch Hydrolysis Test (II Method)
  Gelatin Hydrolysis Test
  Catalase Test
  Oxidase Test
  IMVIC Test
  Extraction of Bacterial DNA
  Medically Significant Gram–Positive Cocci (GPC)
  Protozoans, Fungi, and Animal Parasites
  The Fungi, Part 1–The Yeasts
  Performance Objectives
  The Fungi, Part 2—The Molds
  Viruses: The Bacteriophages
  Serology, Part 1–Direct Serologic Testing
  Serology, Part 2–Indirect Serologic Testing

To study the ability of microorganisms to hydrolyze gelatin with the proteolytic enzyme gelatinase.

The ability of microorganisms to hydrolyze gelatin is commonly taken as evidence that the organism can hydrolyze protein in general. But there are exceptions. Microorganisms vary from species to species with regard to their ability to hydrolyze protein. This feature characterizes some species.

Gelatin is a protein obtained by the hydrolysis of a collagen compound of the connective tissues of animals. It is convenient as a substrate for proteolytic enzymes in microorganisms.

Gelatin is used as the media from the experiment, which is liquid at room temperature and solidifies at –4°C. If the gelatin has been hydrolyzed by the action of organism the media will remain liquid.

  • Nutrient gelatin media
  • Test organism
  • Test tubes
  • Inoculation loop.

  • Preparation of nutrient gelatin media:
  • Composition
  • Peptone – 5 g
  • Gelatin – 20 g
  • Beef extract – 3 g
  • Sodium chloride – 5 g
  • Distilled water – 1000 mL
  • pH–7.2

Different Steps
  1. Media is prepared according to the above given composition.
  2. It is sterilized at 121°C for 15 minutes at 15 lb/square inch and poured into presterilized tubes.
  3. Tubes are allowed to cool and then inoculated with test organisms with 1 inoculated tube used as a control.
  4. Tubes are incubated for 24 hrs and observed for liquefaction of gelatin, after keeping them in ice for half an hour.
Observe your experimental result.

Gelatin is an incomplete protein, lacking many aminoacids, such as tryptophan. When collagen is heated and hydrolyzed, denatured protein gelatin is obtained. Collagen accounts for 90% to 95% of organic matter in the cell. It is the most important protein, rich in amino acids. Microorganisms like bacteria can use gelatin only if they are supplemented with other proteins. Bacteria produce the gelatin-hydrolyzing enzyme gelatinase. Since gelatine is a good solidifying agent at low temperatures, its property of solidification can be used to distinguish between gelatin-hydrolyzing and nonhydrolyzing agents. Most of the Enterobacteriaceae are gelatin-hydrolysis-test–negative. Bacteria like Vibrio, Bacillus, and Pseudomonas are gelatin-positive.


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