1.
Calculate the number of bacteria (CFU/ml) in each serum and saline sample.
Serratia in serum (1:10^2): Approximately 92 x 10^2 bacterial cells were found in 0.5 ml of serum, resulting in a concentration of CFU/ml = 18.4 x 10^3
Serratia in serum (1:10^4): Around 10 x 10^4 bacterial cells were detected in 0.5 ml of serum, leading to a concentration of CFU/ml = 2 x 10^5
Serratia in saline (1:10^6): About 293 x 10^6 bacterial cells were present in 0.5 ml of saline, yielding a concentration of CFU/ml = 5.86 x 10^8
Pseudomonas in serum (1:10^4): Roughly 600 x 10^4 bacterial cells were observed in 0.5 ml of serum, resulting in a concentration of CFU/ml = 12 x 10^6 Pseudomonas in serum (1:10^6): Approximately 65 x 10^6 bacterial cells were identified in 0.5 ml of serum, leading to a concentration of CFU/ml =13 x10^7 Pseudomonas in saline (1:10^4): Around 150x10^4 bacterial cells were found in 0.5ml of saline, resulting in a concentration of CFU/ml=3x10^6
Pseudomonas in saline (1:10^6): About 12x10^6 bacterial cells we represent 0.5ml of saline, yielding a concentration of CFU/ml=2.4x10^7
2.
What was the purpose of the saline?
Bacterial cells undergo bursting in a hypotonic solution due to the osmotic pressure imbalances between the cell's interior and exterior. Using water as a dilution medium would lead to cell lysis, which would negatively impact the experimental outcomes since water is inherently hypotonic. Thus, to prevent any damage to bacterial cells during the serial dilution test, they are diluted in saline to create an isotonic solution. This ensures that the osmotic pressure inside and outside the cells remains balanced, thereby preserving their serial dilution test.
3.
Which bacteria produced more CFU/ml in serum? Why?
Pseudomonas produced a higher number of colony-forming units per milliliter (CFU/ml) in serum compared to Serratia because it can replicate more easily. This is due to the availability of growth factors and the promotion of Pseudomonas growth.
4.
Provide a possible explanation for the ability of
Pseudomonas
to colonize mucous membranes.
Pseudomonas thrives at a temperature of 37 degrees Celsius, equivalent to 98.6 degrees Fahrenheit. As a result, they can thrive in the human body. These bacteria have the ability to grow without oxygen when provided with nitrate. This explains why they flourish particularly well in the lungs - not only do they find optimal conditions for incubation, but they also receive a
consistent source of nitrogen from the air we inhale.
