Exercise 41 Gelatin hydrolysis KTTK (MB. LAB)

Know what substance gelatin was derived from

collagen found in vertebrate connective tissue

Know what gelatinases do and why this is important to the gelatinase
test

hydrolyze gelatin

Gelatinases are family of enzymes certain microorganisms produce and secrete to break down gelatin extracellularly; amino acids are then absorbed

Know what type of molecule is the final result of gelatin hydrolysis

amino acids 

Know how nutrient gelatin differs from most other solid media

the solidifying agent (gelatin) is also the substrate for enzymatic activity.

Know which technique is used to inoculate nutrient gelatin

stab inoculation

Know why (application) the gelatinase test is used

• Used to determine ability of microbe to produce gelatinases
• Can be used to differentiate members of a genus
• Positive Staphylococcus aureus from negativeStaphylococcus epidermidis
• Positive Serratia and Proteus species from negative members of Enterobacteriaceae
• Positive Bacillus anthracis, Bacillus cereus and otherBacillus species
• Positive Clostridium tetani and Clostridium perfringens

Gelatin Hydrolysis test results and interpretations

why it is extremely important to use an uninoculated control to interpret your results

uninoculated control used to verify that any liquefaction is not either temperature related or due to presence of gelatinase

why the nutrient gelatin is incubated at a lower temperature than most of the other tests you have run

Nutrient gelatin melts easily (@ 28 degrees C) so it can result in a false positive

to avoid liquefaction is related to temp.

gelatin hydrolysis test results

some organism can show crateriform liquefaction

does not completely liquefy gelatin

liquefies gelatin in crater formation 

nutrient gelatin stabs - results 1

result 1:

control: gelatinase is absent -

Bacillus subtilis: gelatinase is absent -

Escherichia coli: gelatinase is present +

nutrient gelatin stabs results 2

control: gelatinase is absent -

Bacillus subtilis: gelatinase is absent -

Escherichia coli: gelatinase is present +