Question 1

Which scientist was the first to describe bacteria using a set of lenses, and what type of microscope did he use?

Accepted Answer

Antoni van Leeuwenhoek; light microscope

Question 2

What is the limit of resolution for a typical light microscope, and what does 'resolution' mean in this context?

Accepted Answer

$$0.2\ \mu m$$; the ability to distinguish two adjacent objects as distinct and separate

Question 3

A compound light microscope uses two sets of lenses to form an image. If the objective lens magnifies $$40	imes$$ and the ocular lens magnifies $$10	imes$$, what is the total magnification?

Accepted Answer

$$400	imes$$

Question 4

Which of the following best describes the function of basic dyes in light microscopy?

Accepted Answer

They are positively charged and bind strongly to negatively charged cell components.

Question 5

In a Gram stain, what color do Gram-negative bacteria appear, and what is the reason for this difference?

Accepted Answer

Pink; due to a thin peptidoglycan layer and outer membrane

Question 6

Which type of microscopy uses electrons instead of visible light to image cells and structures, and what is a key requirement for its operation?

Accepted Answer

Electron microscopy; requires operation in a vacuum

Question 7

Which of the following is NOT a type of light microscopy?

Accepted Answer

Scanning electron

Question 8

What was the main conclusion of Louis Pasteur's swan-necked flask experiment?

Accepted Answer

Life does not arise spontaneously from nonliving material.

Question 9

Which of the following best describes Koch's postulates?

Accepted Answer

A set of criteria to prove that a specific microbe causes a specific disease

Question 10

Sergei Winogradsky is best known for which of the following contributions to microbiology?

Accepted Answer

Proposing the concept of chemolithotrophy and demonstrating nitrogen fixation

Question 11

Which of the following statements about ribosomal RNA (rRNA) is correct?

Accepted Answer

rRNA sequences can be used to infer evolutionary relationships among all cells.

Question 12

What is the root of the phylogenetic tree of life, and what does it represent?

Accepted Answer

LUCA; the last universal common ancestor of all cells

Question 13

A researcher wants to isolate a microbe from soil that can oxidize inorganic compounds for energy and use $$CO_2 as a $$carbon source. Which enrichment culture technique should they use, and what type of metabolism are they selecting for?

Accepted Answer

Use inorganic media with $$CO_2$$; select for chemolithoautotrophy

Question 14

Which of the following best describes metagenomics?

Accepted Answer

The recovery and analysis of microbial genomes or fragments from environmental DNA samples

Question 15

Which of the following is a correct application of the formula for total magnification in a compound light microscope?

Accepted Answer

If the objective lens is $$40	imes$$ and the ocular lens is $$10	imes$$, then total magnification is $$40 	imes 10 = 400	imes$$

Question 16

A hospital laboratory is trying to identify the cause of a bacterial infection. They isolate a bacterium from a patient and want to prove it is the causative agent. Which steps should they follow according to Koch's postulates?

Accepted Answer

Isolate the bacterium, infect a healthy host, observe disease, and re-isolate the same bacterium

Question 17

Which of the following statements about the discovery of DNA as the genetic material is correct?

Accepted Answer

Frederick Griffith's experiments with Streptococcus pneumoniae demonstrated transformation, providing evidence that DNA is the genetic material.

Question 18

Which of the following best explains why most microbes have not been cultured yet?

Accepted Answer

They have specific growth requirements that are not met by standard laboratory media.

Question 19

Which of the following statements about the three domains of life is correct?

Accepted Answer

Archaea and Bacteria diverged early, and Eukarya later diverged from Archaea.

CH 1 pt 2 Microscopy, Microbial Cultivation, and the Molecular Basis of Microbial Diversity

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