Question 1

Organisms that live symbiotically inside a larger organism are known as

Accepted Answer

Endosymbionts are organisms that live symbiotically inside a larger organism. Examples of endosymbionts include the mitochondria and chloroplasts in eukaryotic cells. Cyanobacteria are not always endosymbionts and organelles usually refer to specialized structures within a cell rather than entire organisms living inside another organism.

Question 2

Which of the following statements regarding viruses is FALSE?

Accepted Answer

This statement is false as plasmids are actually smaller than viruses. Prions, on the other hand, are even smaller than plasmids.

Question 3

What was the basis for the original smallpox vaccine?

Accepted Answer

The original smallpox vaccine was developed by Edward Jenner in the late 18th century and was based on the cowpox virus. Jenner discovered that milkmaids who had contracted cowpox, a mild and non-lethal illness, were immune to smallpox. He hypothesized that cowpox protected people from smallpox and tested his theory by inoculating a young boy with cowpox and later exposing him to smallpox, which he did not contract. This laid the foundation for the development of the first vaccine, which eventually led to the eradication of smallpox.

Question 4

It took the advent of the polymerase chain reaction to detect the presence of the causative agent for which disease?

Accepted Answer

The polymerase chain reaction (PCR) was pivotal in detecting the presence of HIV, the virus that causes AIDS, due to its ability to amplify tiny amounts of the virus's genetic material, making detection possible even when the virus is present in very low quantities.

Question 5

All of the following are true about penicillin EXCEPT that it

Accepted Answer

Penicillin is produced by a fungus, not a bacterium. Specifically, it is produced by Penicillium fungi.

Question 6

How does the Winogradsky column differ from Koch's plate media?

Accepted Answer

The Winogradsky column is designed to culture a diverse range of microorganisms, including those that can grow on inorganic minerals, demonstrating chemolithotrophy.

Question 7

The word "vaccination" is derived from the Latin word vacca, which means

Accepted Answer

The word "vaccination" comes from the Latin word "vacca," which means "cow." This is because the first vaccine was developed using cowpox virus to protect against smallpox.

Question 8

You have isolated a bacterium that you believe to be the causative agent of a new disease in frogs. How would you test the third of Koch's postulates?

Accepted Answer

The third postulate states that the suspected pathogen must be able to cause the disease in a healthy host. Injecting the isolated bacterium into a healthy frog would allow for observation of disease development, indicating whether the bacterium is indeed the causative agent of the new disease in the frogs.

Question 9

The gene expression machinery of archaea is MOST similar to

Accepted Answer

The gene expression machinery of archaea is most similar to that of eukaryotes, including factors involved in transcription and translation processes.

Question 10

In the three-domain model, the bacterial ancestor of mitochondria derives from ancient

Accepted Answer

According to the three-domain model, the bacterial ancestor of mitochondria derives from respiring bacteria, specifically from the alpha-proteobacteria lineage. This is supported by genetic and biochemical evidence, as well as the endosymbiotic theory, which suggests that mitochondria evolved from a free-living bacterial ancestor that was engulfed by early eukaryotic cells.

Question 11

Which of the following is NOT considered to be an extremophilic condition for bacteria?

Accepted Answer

High nutrients is not considered an extremophilic condition for bacteria. Extremophilic conditions are characterized by extreme environmental factors such as high or low temperature, pH, salt concentration, or pressure. High nutrients, on the other hand, are not necessarily extreme conditions and may actually promote bacterial growth.

Question 12

Suppose Pasteur's swan-necked flasks containing boiled broth became cloudy twenty-four hours after boiling. Which choice could best explain the turbidity or cloudiness in the broth without supporting spontaneous generation?

Accepted Answer

Endospores are resistant to high temperatures and can survive boiling. If the broth was contaminated with endospores, they could survive the boiling process and then grow after the broth had cooled. This would explain the turbidity or cloudiness in the broth without supporting spontaneous generation.

Question 13

Carl Woese's discovery replaced the classification scheme of five kingdoms with a scheme of three

Accepted Answer

Carl Woese's discovery led to the replacement of the classification scheme of five kingdoms with a scheme of three domains: Archaea, Bacteria, and Eukarya.

Question 14

How do many animal endosymbionts grow?

Accepted Answer

Many animal endosymbionts grow in biofilms, which are communities of microorganisms that attach to a surface and produce a protective extracellular matrix. This allows them to access nutrients and resources from the surrounding environment while also protecting them from host immune responses.

Question 15

How did Sergei Winogradsky grow lithotrophs?

Accepted Answer

Sergei Winogradsky grew lithotrophs using an enrichment culture technique. This involves placing the bacteria in a selective growth medium that encourages the growth of only the desired microbes without interference from other organisms. In Winogradsky's case, he used a medium containing sulfur compounds, which was conducive to the growth of lithotrophs that use inorganic compounds as their energy source.

Question 16

The use of agar as a more robust gelling agent in solid media was suggested by

Accepted Answer

Angelina Hesse, the wife of a microbiologist, suggested using agar as a gelling agent in solid media, which was later developed by her husband, Walther Hesse, and became widely adopted in microbiology. None of the other options mentioned agar specifically as a gelling agent.

Question 17

Which of the following organelles are thought to be of prokaryotic origin?

Accepted Answer

Both chloroplasts and mitochondria are thought to have originated from endosymbiosis with free-living prokaryotic organisms. The nucleus, on the other hand, is believed to have evolved from invaginations of the plasma membrane in early eukaryotic cells.

Question 18

Animal microbiomes are NOT significant in

Accepted Answer

Animal microbiomes are not directly involved in converting ammonia to nitrate, a process primarily associated with nitrifying bacteria in soil and water environments, rather than with the microbiomes of animals.

Question 19

In the three-domain model, the bacterial ancestor of chloroplasts derives from ancient

Accepted Answer

Chloroplasts are believed to have originated from ancient cyanobacteria through a process called endosymbiosis, where a cyanobacterium was engulfed by a larger cell and eventually became an integral part of that cell, leading to the development of plants and algae.

Question 20

Penicillin was first used to save the lives of many people during which war?

Accepted Answer

Penicillin was first used during World War II to treat wounded soldiers and became known as the "wonder drug" for its effectiveness in treating infections.

Quiz 1: Microbial Life: Origin and Discovery