B5 - microbiology RP

Question 1

what is the purpose of the microbiology required practical

Answer 1

• know how to culture microorganisms safely and without contaminating the culture
• test how effective substances or different concentrations of substances are at killing and preventing the growth of bacteria
• can also help discover which antibiotics bacteria have become resistant to

Question 2

what is the method for the microbiology required practical

Answer 2

• inoculate a petri dish with a culture of bacteria
• soak small discs of filter paper in different antibiotics
• use sterile forceps, place the discs on the surface of the agar
• incubate the sealed dish upside down at 25 degrees celcius for several days
• measure the diameter of the clear zones around the discs then calculate the area
• the largest zone of inhibition indicates the most effective antibiotic/concentration

Question 3

what is the independent variable in the microbiology required practical

Answer 3

type of antibiotic

Question 4

what is the dependent variable in the microbiology required practical

Answer 4

the size of the zone of inhibition

Question 5

what are the control variables in the microbiology required practical

Answer 5

size of discs, length of time soaked in antibiotic for

Question 6

what would be a useful control in the microbiology required practical

Answer 6

a paper disc with no antibiotic - this would allow a comparison of the effect of the antibiotic

Question 7

how are aseptic techniques used in the microbiology required practical

Answer 7

• wash hands before and after
• sterilise work surfaces before and after
• use a sterile petri dish to ensure no microorganisms are already present
• sterilise inoculating loop by holding it in bunsen burner until it glows red
• work near a bunsen burner
• minimise the time that the agar is exposed to air
• seal with tape but not fully as anaerobic bacteria could grow
• incubate at 25 degrees celcius which is below the optimum temperature for pathogens to grow