Question 1

You are measuring growth in a bacterial culture. The number of viable cells remains constant, and when you check the medium, you find that the carbon source has been used up. In which phase of growth is the culture?

Accepted Answer

The culture is in the stationary phase where the growth rate slows down, and the number of viable cells reaches a plateau due to the depletion of nutrients like carbon source.

Question 2

Why can't most organisms use the nitrogen gas that is so prevalent in the atmosphere? How do these organisms acquire a usable form of nitrogen?

Accepted Answer

The answer of Why can't most organisms use the nitrogen...

Question 3

Compare and contrast complex media, synthetic media, and enriched media.

Accepted Answer

The answer of Compare and contrast complex media, synthetic media,...

Question 4

How do scientists know of the existence of "unculturable" organisms?

Accepted Answer

The answer of How do scientists know of the existence...

Question 5

When studying the metabolism of an organism, why is it better to grow organisms in a defined synthetic medium instead of a complex medium?

Accepted Answer

The answer of When studying the metabolism of an organism,...

Question 6

What type of medium and conditions would you need to have in order to select for photoautotrophs?

Accepted Answer

The answer of What type of medium and conditions would...

Question 7

What is the classic approach for finding new antibiotics?

Accepted Answer

The classic approach for finding new antibiotics is to screen bacteria and fungi for secreted antimicrobial compounds. This is because these microorganisms have evolved various defense mechanisms to compete with each other for resources and limiting factors in their environment, including the production of antimicrobial compounds. Therefore, screening these microorganisms for their secretions can lead to the discovery of new antibiotics.

Question 8

A cafeteria worker who fails to wash his hands thoroughly and fails to wear gloves inoculates a quiche with 4 E. coli cells when he uses his finger to test whether it is done. By the time you purchase the quiche, there are 128 E. coli cells in it. How many generations did the cells go through?

Accepted Answer

The number of generations can be calculated using the formula 2^n = final number of cells / initial number of cells. Here, 2^n = 128 / 4, which simplifies to 2^n = 32. Therefore, n = 5 generations.

Question 9

Define the terms "viable" and "viable but unculturable." Why are so many environmental organisms believed to be viable but unculturable?

Accepted Answer

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Question 10

The shortest lag period would most likely be observed in the transfer

Accepted Answer

When transferring from complex medium to fresh complex medium, the nutritional requirements are similar and the organism can easily adapt, leading to a shorter lag phase or even no lag phase. In contrast, transferring to a different type of medium or altering environmental factors like temperature, pH, or salt concentration can cause stress and lead to longer lag phases.

Question 11

Which of the following genera does NOT undergo differentiation?

Accepted Answer

Escherichia is a unicellular organism that does not undergo differentiation. The other genera listed are known to undergo differentiation into various morphological or functional forms. Anabaena is known for its ability to form heterocysts, Bacillus can form endospores, Clostridium can form endospores and also exhibit pleomorphism, and Streptomyces are known for their ability to form aerial mycelia and spores.

Question 12

Compare and contrast the ABC transporters and group translocation in terms of energy requirements and concentration gradients.

Accepted Answer

The answer of Compare and contrast the ABC transporters and...

Question 13

In order to grow unculturable environmental microbes, Kim Lewis and colleagues derived the iChip. What is the purpose of this device?

Accepted Answer

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Question 14

Which of the following is true of all biofilms?

Accepted Answer

All biofilms have an extracellular polymeric substance (EPS) that is secreted by the bacteria. This EPS is composed of a variety of molecules, including polysaccharides, nucleic acids, and lipids. It is a key component of the biofilm matrix and is responsible for the adhesion and cohesion of the bacterial cells within the biofilm.

Question 15

How do some cyanobacteria fix nitrogen while growing aerobically?

Accepted Answer

Some cyanobacteria have specialized cells called heterocysts that lack oxygen and protect the nitrogenase enzyme from oxygen damage, allowing nitrogen fixation to occur even in the presence of oxygen.

Question 16

MacConkey medium contains bile salts, crystal violet, lactose, and the pH indicator neutral red. Some organisms can ferment lactose, producing acids as a by-product. Is this medium likely to be selective and/or differential? Explain.

Accepted Answer

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Question 17

Why is iron so often a limiting nutrient, when it seems to be so abundant in the environment, and how can organisms overcome this problem?

Accepted Answer

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Question 18

During biofilm formation, as more and more cells bind to the surface, they begin sending signals to each other in a process called

Accepted Answer

During biofilm formation, cells communicate with each other by sending and detecting signaling molecules. This process is called quorum sensing, and it allows the cells to coordinate their behavior and switch from individual cells to a community structure. Therefore, choice A - quorum sensing - is the correct answer. The other options are not directly related to cell-cell communication and biofilm formation.

Question 19

Some bacteria form environmentally resistant dormant forms called

Accepted Answer

Endospores are formed by some bacteria as a survival strategy. They are a highly resistant and dormant form that can withstand extreme environmental conditions such as heat, radiation, and desiccation. Heterocysts are specialized cells found in some cyanobacteria that are involved in nitrogen fixation. Colonies are groups of individual bacteria that grow together in a community, while hyphae are thread-like structures formed by some fungi. Actinomycetes are a group of bacteria that have filamentous growth patterns.

Question 20

Compare and contrast the difference between electrogenic and electroneutral coupled transport and give an example of each.

Accepted Answer

The answer of Compare and contrast the difference between electrogenic...

Quiz 4: Bacterial Culture, Growth, and Development