Lab 7 Microbial Control BIO250L
Student Name:
Access Code (located on the lid of your lab kit):
Experiment 1- Effect of Chemical Germicides on Bacterial Growth
Table 3: Experiment Results
Sample Germicide Zone of Inhibition (mm) Relative Effectiveness
10% Bleach 20 100
70% Isopropyl
20 100
Skin Alcohol
Hibiclens™ 20 100
Control 0 0
10% Bleach 20 100
70% Isopropyl
20 100
Nose Alcohol
Hibiclens™ 20 100
Control 0 0
10% Bleach 20 100
70% Isopropyl
20 100
Throat Alcohol
Hibiclens™ 20 100
Control 0 0
10% Bleach 20 100
70% Isopropyl
20 100
Shoe Alcohol
Hibiclens™ 20 100
Control 0 0
Post-Lab Questions
1. Which germicide was the most effective? Was the same germicide most effective for bacteria
isolated from the different sources? What could explain this finding?
, Lab 7 Microbial Control BIO250L
We did not find a difference in effectiveness. We could have had this happen because the bacteria did
not grow or they were dead before the germicides were applied.
2. Which germicide was the least effective? Was the same germicide least effective for bacteria isolated
from different sources? What could explain this finding?
We did not find a difference in effectiveness. However, in theory, the Hibiclens would be least effective
because it affects the cell wall of the gram positive much more than a gram negative cell wall. We could
have had this happen because the bacteria did not grow or they were dead before the germicide was
applied.
3. Were any bacteria from a specific source most resistant to the different germicides? If so, which
source?
Either they were all resistant to all germicides or there was nothing to be kill.
4. Did the dry filter paper serve as a positive or negative control?
It served as a negative control because it did not contain any substance.
5. Look up the chemical formulas for bleach, isopropyl alcohol, and chlorhexidine gluconate (the active
ingredient in Hibiclens). How does each chemical achieve its germicidal properties?
Bleach and alcohol works by denaturing the protein. Hibiclens works by destroying the cell wall.
Insert photo of your cultures after incubation with your name clearly visible in the background:
Student Name:
Access Code (located on the lid of your lab kit):
Experiment 1- Effect of Chemical Germicides on Bacterial Growth
Table 3: Experiment Results
Sample Germicide Zone of Inhibition (mm) Relative Effectiveness
10% Bleach 20 100
70% Isopropyl
20 100
Skin Alcohol
Hibiclens™ 20 100
Control 0 0
10% Bleach 20 100
70% Isopropyl
20 100
Nose Alcohol
Hibiclens™ 20 100
Control 0 0
10% Bleach 20 100
70% Isopropyl
20 100
Throat Alcohol
Hibiclens™ 20 100
Control 0 0
10% Bleach 20 100
70% Isopropyl
20 100
Shoe Alcohol
Hibiclens™ 20 100
Control 0 0
Post-Lab Questions
1. Which germicide was the most effective? Was the same germicide most effective for bacteria
isolated from the different sources? What could explain this finding?
, Lab 7 Microbial Control BIO250L
We did not find a difference in effectiveness. We could have had this happen because the bacteria did
not grow or they were dead before the germicides were applied.
2. Which germicide was the least effective? Was the same germicide least effective for bacteria isolated
from different sources? What could explain this finding?
We did not find a difference in effectiveness. However, in theory, the Hibiclens would be least effective
because it affects the cell wall of the gram positive much more than a gram negative cell wall. We could
have had this happen because the bacteria did not grow or they were dead before the germicide was
applied.
3. Were any bacteria from a specific source most resistant to the different germicides? If so, which
source?
Either they were all resistant to all germicides or there was nothing to be kill.
4. Did the dry filter paper serve as a positive or negative control?
It served as a negative control because it did not contain any substance.
5. Look up the chemical formulas for bleach, isopropyl alcohol, and chlorhexidine gluconate (the active
ingredient in Hibiclens). How does each chemical achieve its germicidal properties?
Bleach and alcohol works by denaturing the protein. Hibiclens works by destroying the cell wall.
Insert photo of your cultures after incubation with your name clearly visible in the background:
