Quiz 3 Calculation and methods SEPT 2023

Which technique involves using a sterilized loop to spread a small volume of microbial culture over the surface of a solid agar medium?

• a) Pour plate

• b) Streaking

• c) Loop dilution

• d) Colony counting

If a microbial culture is diluted 10-fold, and 1 mL of the diluted sample is plated, resulting in the growth of 50 colonies, what is the colony count in the original undiluted sample?

• a)       5 colonies/mL

• a)       50 colonies/mL

• a)      500 colonies/mL

• a)       5000 colonies/mL

In microbiology, turbidity is commonly measured as an indicator of bacterial growth. Which instrument is commonly used for the quantitative measurement of turbidity in a microbial culture?

• Spectrophotometer

• Centrifuge

• Microscope

• pH meter

What is the purpose of flame sterilizing the inoculating loop between streaks in streak plate technique?

• a) To cool down the loop

• b) To prevent contamination

• c) To improve visibility of colonies

• d) To enhance microbial growth

Plate count method is used for:

• Measuring turbidity

• Estimation of protein content

• Enumeration of viable microorganisms

• Estimation of DNA content

If a bacterial culture is diluted 1:100, and 0.1 mL of the diluted sample is plated, resulting in the growth of 80 colonies, what is the colony count in the original undiluted sample?

• 800 colonies/mL

• 8 000 colonies/mL

• 80 000 colonies/mL

• 800 000 colonies/mL

What is the unit of measurement for turbidity in a microbial culture using a spectrophotometer?

• Absorbance

• pH

• Viscosity

• Conductivity

The streak plate technique is primarily used for:

• Determining cell density

• Isolating pure colonies

• Measuring turbidity

• Assessing metabolic activity

If a microbial sample is diluted 1:1000, and 0.01 mL of the diluted sample is plated, resulting in the growth of 25 colonies, what is the colony count in the original undiluted sample?

• 250 colonies/mL

• 2500 colonies/mL

• 250 000 colonies/mL

• 25 000 000 colonies/mL

How does an increase in microbial cell density affect turbidity readings in a culture measured by a spectrophotometer?

• a) Turbidity decreases

• b) Turbidity remains constant

• c) Turbidity increases

• d) Turbidity is not related to cell density