W1 quiz

Question 1

What are the defining features of microorganisms?

Answer 1

<1mm diameter
simple organisation
qbiquitous

Question 2

Why are the streak plate method and aseptic technique important in identifying bacteria?

Answer 2

To avoid contamination
To obtain a pure culture of only ONE type of organism
To separate microorganisms from a mixed culture

Question 3

How do the majority of bacteria grow?

Answer 3

By binary fission

Question 4

What is the correct order for the phases of growth of a single-celled microorganism in a closed system?

Answer 4

Lag
Log (exponential)
Stationary
Death

Question 5

What environmental factors may affect microbial growth?

Answer 5

Temperature
Water
pH
Atmosphere
Light

Question 6

Which methods can be used to control microbial growth?

Answer 6

Heat sterilisation
Filtration
Radiation

Question 7

What is the difference between a simple and differential stain?

Answer 7

A simple stain provides information about the morphology of bacteria while a differential stain distinguishes between types of bacteria based on physical or chemical properties of, for example, the cell wall.

Question 8

In which order should the dyes and reagents be applied to the slide of heat-fixed bacteria when Gram staining?

Answer 8

1. Crystal Violet
2. Iodine
3. Alcohol
4. Safranin

Question 9

What is the difference between a Gram-positive and Gram-negative cell wall?

Answer 9

Gram-positive cell walls are 90% peptidoglycan and do not have an outer membrane while Gram-negative cell walls are 10% peptidoglycan and do have an outer membrane.

Question 10

In the Gram stain procedure, a thick smear of bacteria is problematic because:

Answer 10

• The smear stains unevenly
• A false positive result may be obtained
• Individual cells are hard to find