growing cultures

Question 1

method

Answer 1

1. sterile nutrient agar in Petri dish
2. sterilise inoculating loop - pass through Bunsen burner flame
3. dip loop into bacterial culture - streak onto agar plate
4. close lid not fully - with tape
5. incubate at ~ 25 degrees
6. observe colony growth

Question 2

serial dilution

Answer 2

1. take 1cm3 of sample of broth and mix into 9cm3 of distilled water (1:10)
2. spread 0.1 cm3 onto each agar plate
3. incubate
4. count visible colonies
5. calculate original population size using: Number of bacteria = number of colonies x dilution factor

Question 3

why is serial dilutions necessaty

Answer 3

• reduce population density
• because counting number of microorganisms is too much in broth