Question 1

Which of the following best describes a biofilm?

Accepted Answer

A community of microorganisms protected by a polysaccharide and protein matrix.

Question 2

During which stage of biofilm development do cells multiply and produce extracellular polymeric substances (EPS)?

Accepted Answer

Colonization

Question 3

What is the main function of the extracellular polymeric substance (EPS) in a biofilm?

Accepted Answer

It acts as a sticky matrix that supports biofilm structure and protects cells from harmful conditions.

Question 4

Quorum sensing in bacteria is best described as:

Accepted Answer

A process by which bacteria detect their own population density using extracellular signaling molecules.

Question 5

In a closed system, which phase of microbial growth is characterized by the synthesis of enzymes required for cell growth, but not an increase in cell number?

Accepted Answer

Lag phase

Question 6

During which phase of the bacterial growth curve are the rates of cell production and cell death approximately equal?

Accepted Answer

Stationary phase

Question 7

Which of the following equations best represents the logarithmic increase in cell number during the exponential phase of bacterial growth?

Accepted Answer

$$N_t = N_0$ 	imes 2$$^{n}$$

Question 8

A pure culture of bacteria is defined as:

Accepted Answer

A population of cells containing only one species that grows from a single colony.

Question 9

Which of the following statements about the stationary phase of bacterial growth is correct?

Accepted Answer

Nutrient levels are depleted and the number of viable cells remains constant.

Question 10

Which type of metabolites are produced during the late log phase and are required for cell survival?

Accepted Answer

Secondary metabolites

Question 11

A bacterial culture grown in a closed system will stop growing when:

Accepted Answer

The limited nutrients have been consumed.

Question 12

Which of the following best describes the function of quorum sensing in a biofilm?

Accepted Answer

It allows bacteria to detect and respond to changes in population density by producing and sensing signaling molecules.

Question 13

During which phase of the bacterial growth curve are secondary metabolites most likely to be produced?

Accepted Answer

Late log phase

Question 14

Which of the following is NOT a characteristic of a biofilm?

Accepted Answer

Cells are always genetically identical to each other.

Question 15

What is the main reason that bacteria in a biofilm are more resistant to antibiotics than planktonic (free-living) bacteria?

Accepted Answer

The EPS matrix limits the penetration of antibiotics and facilitates gene transfer.

Question 16

Which of the following best describes the log (exponential) phase of bacterial growth?

Accepted Answer

Cells are dividing at a constant and rapid rate.

Question 17

In a rapidly multiplying bacterial population, cell numbers increase:

Accepted Answer

Logarithmically.

Question 18

Which of the following is a correct statement about primary metabolites?

Accepted Answer

They are produced during the early log phase and are used for normal cell growth.

Question 19

Which of the following best explains why a pure culture is important in microbiology experiments?

Accepted Answer

It ensures that observed effects are due to a single species, reducing experimental variability.

Question 20

During which phase of biofilm development do cells detach to create new biofilms?

Accepted Answer

Dispersal

Microbial Growth, Biofilms, and Culture Methods

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