Question 1

Which of the following best describes the primary meaning of 'microbial growth' in microbiology?

Accepted Answer

An increase in the number of microbial cells

Question 2

A patient sample is collected for bacterial culture. Which of the following is MOST important to ensure accurate diagnosis?

Accepted Answer

Delivering the specimen to the lab in a timely manner

Question 3

Which type of culture medium would you use to isolate a bacterium that can grow in the presence of high salt concentrations, and why?

Accepted Answer

Selective medium, because it inhibits the growth of non-halophiles

Question 4

During which phase of the bacterial growth curve are cells most susceptible to antibiotics that target cell wall synthesis?

Accepted Answer

Log (exponential) phase

Question 5

A bacterium that uses light as an energy source and CO$$_2 as a $$carbon source is classified as a:

Accepted Answer

Photoautotroph

Question 6

Which of the following toxic oxygen species is MOST reactive and damaging to cells?

Accepted Answer

Hydroxyl radical ($$OH\cdot)$$

Question 7

Obligate anaerobes are killed by oxygen because they:

Accepted Answer

Lack enzymes such as superoxide dismutase and catalase

Question 8

Nitrogen fixation is essential for life on Earth because:

Accepted Answer

It converts $$N_2$$ into ammonia ($$NH_3$$), which can be used by plants and other organisms

Question 9

A bacterium isolated from a hot spring that grows optimally at 70$$^	ext{o}C is $$best classified as a:

Accepted Answer

Thermophile

Question 10

Which of the following best explains why most bacteria cannot grow in highly acidic environments?

Accepted Answer

Acidic conditions denature proteins by disrupting hydrogen bonds

Question 11

Which of the following statements about biofilms is TRUE?

Accepted Answer

Biofilms can form on both abiotic and biotic surfaces

Question 12

Quorum sensing in bacteria is best described as:

Accepted Answer

A mechanism for cell-to-cell communication using autoinducers to regulate gene expression

Question 13

Which of the following is a real-world example of a biofilm?

Accepted Answer

Dental plaque on teeth

Question 14

A facultative anaerobe is characterized by which of the following?

Accepted Answer

It can grow with or without oxygen, but grows better with oxygen

Question 15

Which enzyme is responsible for converting superoxide radicals ($$O_2$$^-$$) into hydrogen peroxide (H_2O_2$)?

Accepted Answer

Superoxide dismutase

Question 16

A bacterial culture is growing in a medium with a pH of 9.5. This bacterium is most likely a(n):

Accepted Answer

Alkalinophile

Question 17

Which of the following best describes the role of exopolysaccharides in biofilm formation?

Accepted Answer

They form a protective matrix that encases the microbial community

Question 18

A defined (synthetic) medium for culturing E. coli contains which of the following as a carbon source?

Accepted Answer

Glucose

Question 19

Which of the following is a correct multi-step sequence for the development of a mature biofilm?

Accepted Answer

Initial interaction → Stable adhesion → Microcolony formation → Exopolysaccharide synthesis

Question 20

Which of the following best explains why biofilm-associated bacteria are more resistant to antibiotics than planktonic bacteria?

Accepted Answer

The biofilm matrix acts as a molecular filter, reducing drug penetration

Microbial Nutrition, Growth, and Biofilms: Study Notes

Study Guide - Practice Questions