Q: Which of the following equations correctly calculates colony forming units per milliliter ($$CFU/ml) $$when 0.1 ml of a diluted sample is plated and 50 colonies are counted, with a dilution factor of $$10^{-3}$$?

$$CFU/ml = \frac{\text{Number of colonies}}{\text{Volume plated (ml)}} \times \text{Dilution factor}$$

Question 1

Which of the following statements best distinguishes Archaea from Bacteria?

Accepted Answer

Archaea have unique membrane lipids and lack peptidoglycan, while Bacteria have peptidoglycan in their cell walls.

Question 2

Which scientist is credited with disproving the theory of spontaneous generation using a swan-neck flask experiment?

Accepted Answer

Louis Pasteur

Question 3

A patient presents with a bacterial infection. The lab technician performs a Gram stain and observes pink cells under the microscope. Which structural feature is most likely present in these bacteria?

Accepted Answer

A thin peptidoglycan layer and an outer membrane containing lipopolysaccharide (LPS)

Question 4

Which of the following is a beneficial activity of microorganisms in the environment?

Accepted Answer

Fixing atmospheric nitrogen into usable forms for plants

Question 5

A microbiologist wants to observe the internal structure of a bacterial cell in high detail. Which microscopy technique should they use?

Accepted Answer

Transmission electron microscopy (TEM)

Question 6

Which of the following best describes the mechanism of the Gram stain?

Accepted Answer

Crystal violet stains cells, iodine forms a complex, alcohol decolorizes Gram-negative cells, and safranin counterstains them.

Question 7

Which of the following equations correctly calculates colony forming units per milliliter ($$CFU/ml) $$when 0.1 ml of a diluted sample is plated and 50 colonies are counted, with a dilution factor of $$10^{-3}$$?

Accepted Answer

$$CFU/ml = \frac{	ext{Number of colonies}}{	ext{Volume plated (ml)}} 	imes 	ext{Dilution factor}$$

Question 8

Which of the following is NOT a major characteristic used to differentiate the three domains (Bacteria, Archaea, Eukarya)?

Accepted Answer

Mode of reproduction

Question 9

A newly discovered microbe is classified by comparing its DNA base composition with known organisms. Which method is most appropriate for this analysis?

Accepted Answer

Determining the percentage of guanine and cytosine ($$\%GC) $$content

Question 10

Which of the following best explains why ribosomal RNA (rRNA) is especially useful in studying evolutionary relationships among organisms?

Accepted Answer

rRNA sequences are highly conserved and found in all living cells.

Question 11

Which of the following stains would be most appropriate to visualize bacterial endospores?

Accepted Answer

Endospore stain

Question 12

A scientist is using a compound microscope and wants to maximize resolution. Which of the following actions will best achieve this?

Accepted Answer

Increasing the numerical aperture and using oil immersion

Question 13

Which of the following is a plausible reason why the outcome of a Gram stain may be affected by the age of the bacterial culture?

Accepted Answer

Older cultures may have damaged cell walls, leading to incorrect Gram reaction.

Question 14

Which of the following best describes the difference between simple and differential staining?

Accepted Answer

Simple staining reveals cell morphology, while differential staining distinguishes between different types of cells.

Question 15

Which of the following is a medically significant feature of the glycocalyx in bacteria?

Accepted Answer

It helps bacteria evade phagocytosis by host immune cells.

Question 16

Which of the following best defines 'binomial nomenclature'?

Accepted Answer

A system that uses genus and species names to uniquely identify organisms.

Question 17

Which of the following is a correct application of Koch’s postulates?

Accepted Answer

Demonstrate that the pathogen causes disease when introduced into a healthy host.

Question 18

Which of the following best describes the difference between prokaryotic and eukaryotic cells?

Accepted Answer

Prokaryotic cells lack a nucleus, while eukaryotic cells have a nucleus.

Question 19

Which of the following is the best example of group translocation in prokaryotic cells?

Accepted Answer

Transport of glucose into the cell with simultaneous phosphorylation

Fundamentals of Microbiology: Core Concepts and Study Guide

Study Guide - Practice Questions

Study Guide - Flashcards