Topic 6 - Microbiology & Pathogens

Question 1

What does it mean to culture microorganisms?

Answer 1

Culturing refers to growing large numbers of microorganisms (so that they can be properly analysed).

Question 2

How should you dispose of a culture?

Answer 2

Seal the culture in a plastic bag and sterilise them at 121℃ for 15 minutes under high pressure.

Question 3

what are the 2 main types of nutrient medium?

Answer 3

Nutrient broth (liquid) & Nutrient agar (solid).

Question 4

what is it called when a nutrient medium has very specific nutrients added to it?

Answer 4

A selective medium.

Question 5

What is selective medium especially useful for?

Answer 5

Identifying microorganisms that have been genetically modified.

Question 6

What does inoculation mean?

Answer 6

Inoculation refers to the introduction of a microorganism to a nutrient medium.

Question 7

What is the purpose of streaking agar?

Answer 7

Streaking is a technique used to isolate a pure strain from a single species of microorganism.

Question 8

What do Indicator media do?

Answer 8

• Indicator Media cause certain types of Bacteria to change colour.
• Bacteria that change colour (or don’t) can then be Isolated & cultured.

Question 9

What is a Haemocytometer?

Answer 9

• The Haemocytometer is a specialised Microscope slide which aids in the manual counting of cells under a microscope.

Question 10

What was the Haemocytometer initially made to count before it was used to count bacterial cells?

Answer 10

The Haemocytometer was initially invented to count Blood Cells.

Question 11

How does the Haemocytometer work?

Answer 11

• Each corner of the Haemocytometer grid has a square divided into 16 smaller squares.
• The number of cells in each of these 4 big squares is counted and the mean is found.
• The Haemocytometer is calibrated so that the number of cells in one big square equals the number of cells x10^4 per cm^3 of medium.
• This enables us to calculate the number of Microorganisms in a standard volume of medium.