October 13

Three tasks were given
1. Conduct a Starch Hydrolysis Test
2. Conduct a Casein Hydrolysis Test
3. Conduct a Fat Hydrolysis Test

Pre-incubation

Post incubation after 48 hours

STARCH HYDROLYSIS TEST

Purpose: To distinguish if the bacteria can hydrolyze (digest) in Starch.

Materials:
Starch agar plate
Gram's iodine
pure culture of unknown bacteria "K" in agar slant 

 Procedure:
1. Label the bottom of a starch agar plate with my name and sample name. initial and date
2. Use aseptic technique to inoculate the starch agar plate by streaking a short line on the agar surface with a loopful of bacteria from my agar slant. 
3. Inoculate the plate upside-down at 37 degrees C for 48 hours.
4. After incubation, flood the starch agar surface with Gram's Iodine. Wait 30sec to 1 min for a purple-black color to develop that indicates where starch is present in the agar. 
5. A clear area around a bacteria growth is a positive test for starch hydrolysis. If color apears around the growth, the test is negative.

mine is on the right hand side: positive test.

6. Discard the plate in the designated place for sterilization. 


RESULTS: Positive test for starch hydrolysis. 




CASEIN HYDROLYSIS TEST


Purpose: To distinguish the ability of the bacteria to hydrolyze (digest) casein, the major protein in milk.

Materials:
Skim milk agar plate
pure culture of unknown bacteria "K" in agar slant 

 Procedure:
1. Label the bottom of the skim milk agar plate with my name and sample name. initial and date
2. Use aseptic technique to inoculate the skim milk agar plate by streaking a short line on the agar surface with a loopful of bacteria from my agar slant. 
3. Inoculate the plate upside-down at 37 degrees C for 48 hours.

4. After incubation, examine the plate. A positive test yields a clear zone around the bacteria growth on the plate. A negative test yields a white area around where the bacteria would be.
5. Discard the plate in the designated place for sterilization. 


PICTURE
 
RESULTS: Negative for casein hydrolysis 

Mine is on the right: Slight whiteness = negative test

FAT (TRIGLYCERIDE) HYDROLYSIS TEST


Purpose: To distinguish the ability of the bacteria to hydrolyze (digest) a triglyceride, a type of lipid.

Materials:
Tributyrin agar plate
pure culture of unknown bacteria "K" in agar slant 

 Procedure:
1. Label the bottom of the tributyrin agar plate with my name and sample name. initial and date
2. Use aseptic technique to inoculate the tributyrin agar plate by streaking a short line on the agar surface with a loopful of bacteria from my agar slant. 
3. Inoculate the plate upside-down at 37 degrees C for 48 hours.

4. After incubation, examine the plate. A positive test yields a clear zone around the bacteria growth on the plate. A negative test results in no clearing around the growth.
5. Discard the plate in the designated place for sterilization. 

Mine is on the Left: Negative

 

RESULTS: Negative for fats (triglycerides)