6.1 - Bacteria test mistakes

Question 1

Compare and contrast the structure of the cell wall of Gram positive and Gram negative bacteria.

Answer 1

Both contain peptidoglycan
Gram positive have a thicker peptidoglycan layer than Gram negative bacteria.
Gram positive walls contain teichoic acid whereas Gram negative do not.

Question 2

Devise a method to investigate 4 different types of antibiotics.

Answer 2

Use the same species of bacteria.
Use an agar growth medium.
Work near a bunsen flame.
Measure zone of inhibition
Use same volume of antibiotic
Incubate between 25-30 degrees for over a day

Question 3

Evaluate the use of dilution plating and optical methods for determining the number of bacterial cells in a culture.

Answer 3

Optical methods quicker to obtain results because incubation is needed for dilution plating.
Dilution plating gives a direct count but optical methods give a turbidity reading.
Dilution plating requires easily available apparatus but optical methods require a colorimeter.
Optical methods produce error if tube is not shaken, plating has risk of error if colonies run into each other.