Question 1

Which of the following best describes a biofilm and its significance in clinical microbiology?

Accepted Answer

A biofilm is a community of microorganisms attached to a surface and encased in a self-produced matrix; it is important because it increases resistance to antimicrobial agents.

Question 2

Which of the following media types would be most appropriate for isolating a specific bacterial species from a mixed sample, and why?

Accepted Answer

Selective media, because it inhibits the growth of unwanted organisms while allowing the target organism to grow.

Question 3

A microbiologist is culturing E. coli in a laboratory. Which phase of the bacterial growth curve is characterized by exponential increase in cell number, and what is the mathematical expression for this growth?

Accepted Answer

Log (exponential) phase; $N_t = N_0 e^{r t}$

Question 4

Which of the following best distinguishes between sterilization and disinfection?

Accepted Answer

Sterilization destroys all forms of microbial life including spores, while disinfection eliminates most pathogenic microorganisms but not necessarily spores.

Question 5

A hospital is using a disinfectant that targets bacterial cell membranes. Which mechanism of action is most likely involved?

Accepted Answer

Disruption of plasma membrane integrity, leading to leakage of cellular contents.

Question 6

Which microbial characteristic would make a bacterium more resistant to disinfectants and antiseptics?

Accepted Answer

Ability to form endospores.

Question 7

Which of the following best describes the difference between genotype and phenotype?

Accepted Answer

Genotype is the genetic makeup of an organism, while phenotype is the expression of those genes as observable traits.

Question 8

During DNA replication in bacteria, which enzyme is responsible for synthesizing the new DNA strand, and what is the direction of synthesis?

Accepted Answer

DNA polymerase; 5' to 3'

Question 9

A mutation changes a single nucleotide in a gene, resulting in a different amino acid in the protein. What type of mutation is this, and what effect might it have?

Accepted Answer

Missense mutation; may alter protein function depending on the amino acid change.

Question 10

Which of the following best describes horizontal gene transfer in bacteria?

Accepted Answer

Transfer of genetic material between unrelated cells, often via plasmids, transformation, conjugation, or transduction.

Question 11

Which process involves the uptake of naked DNA from the environment by a bacterial cell?

Accepted Answer

Transformation

Question 12

A scientist uses restriction enzymes to cut DNA at specific sequences. Which biotechnology tool is being utilized, and what is the typical recognition sequence format?

Accepted Answer

Restriction enzymes; $5' - GAATTC - 3'$

Question 13

Which of the following is a real-world application of recombinant DNA technology in medicine?

Accepted Answer

Production of synthetic insulin using genetically modified bacteria.

Question 14

A researcher wants to amplify a specific DNA segment for analysis. Which technique should they use, and what is the basic formula for the number of DNA copies after $n$ cycles?

Accepted Answer

Polymerase Chain Reaction (PCR); $2^n$

Question 15

Which of the following is an ethical concern associated with biotechnology?

Accepted Answer

Risk of unintended consequences from genetically modified organisms released into the environment.

Question 16

Which of the following best describes the function of plasmids in bacterial genetic change?

Accepted Answer

Plasmids are small, circular DNA molecules that can carry genes for antibiotic resistance and can be transferred between cells.

Question 17

A bacterial cell is exposed to a mutagen that causes a frameshift mutation. What is the most likely outcome for the protein encoded by the affected gene?

Accepted Answer

The protein will likely be nonfunctional due to extensive changes in the amino acid sequence.

Question 18

Which of the following best describes the difference between selective and differential media?

Accepted Answer

Selective media inhibits the growth of certain organisms, while differential media allows differentiation based on observable characteristics.

Question 19

Which of the following is a mechanism by which transposons contribute to genetic change in bacteria?

Accepted Answer

Transposons move genetic material within and between DNA molecules, potentially disrupting genes or conferring new traits.

Microbiology Study Guide: Bacterial Growth, Microbial Control, Genetics, and Biotechnology

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