Microbial Growth Chapter 6 Clicker Questions

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Questions and Answers

Which organism is killed by atmospheric oxygen?

  • Aerotolerant anaerobe
  • Obligate aerobe
  • Facultative anaerobe
  • Obligate anaerobe (correct)

In bacteria, toxic hydrogen peroxide can be broken down into water and oxygen by the enzyme:

  • Catalase (correct)
  • Superoxide dismutase
  • Hydroxylase
  • Peroxidase

What can be best defined as the time it takes for a cell to divide?

  • The time it takes for a cell to divide (correct)
  • The length of time it takes for lag phase
  • The duration of log phase
  • How many generations a cell can divide

Bacterial growth is usually graphed using ________ scales.

<p>Logarithmic (semi-logarithmic) (B)</p> Signup and view all the answers

In which growth phase is there intense activity preparing for population growth, but no increase in population?

<p>Lag phase (D)</p> Signup and view all the answers

In which growth phase is there intense activity preparing for population growth, but no increase in population?

<p>Lag phase (A)</p> Signup and view all the answers

Which of the following is NOT a possible reason why exponential growth stops?

<p>Bacteria becoming dormant (B)</p> Signup and view all the answers

In the stationary phase, what happens to microbial deaths and new cell formation?

<p>The number of microbial deaths is equal to the number of new cells formed. (D)</p> Signup and view all the answers

Which type of medium suppresses the growth of unwanted bacteria and encourages growth of desired microbes?

<p>Selective medium (D)</p> Signup and view all the answers

What is the optimum pH for MOST bacteria?

<p>7 (C)</p> Signup and view all the answers

At what temperature would you expect a psychrophile to have its optimal growth?

<p>15°C (A)</p> Signup and view all the answers

What are organisms that require high salt concentrations for growth called?

<p>Obligate Halophiles (A)</p> Signup and view all the answers

What is the primary energy source utilized by primary producers in hydrothermal vents on the ocean floor?

<p>Hydrogen sulfide (D)</p> Signup and view all the answers

Why does the addition of salts preserve foods?

<p>Lower osmotic pressure (C)</p> Signup and view all the answers

What is the optimal temperature for psychrophiles?

<p>+15°C (D)</p> Signup and view all the answers

Which type of organisms prefer acidic environments?

<p>Acidophiles (C)</p> Signup and view all the answers

'Thermophiles' are organisms that thrive in which type of environment?

<p>+50°C - +80°C range (D)</p> Signup and view all the answers

What is the primary purpose of adding salts to preserve foods?

<p>To increase osmotic pressure (A)</p> Signup and view all the answers

From where do chemoautotrophs and photoautotrophs derive their carbon?

<p>Carbon dioxide (C)</p> Signup and view all the answers

What process involves some microorganisms using gaseous nitrogen directly from the atmosphere?

<p>Nitrogen fixation (B)</p> Signup and view all the answers

What do you call an organism that can grow without oxygen but uses it when present?

<p>Facultative anaerobe (C)</p> Signup and view all the answers

Which type of organism is susceptible to being killed by atmospheric oxygen?

<p>Obligate aerobe (D)</p> Signup and view all the answers

What effect does adding salts have on the osmotic pressure of foods?

<p>Increase osmotic pressure (D)</p> Signup and view all the answers

Which compound is the primary source of carbon for chemoautotrophs and photoautotrophs?

<p>Carbon dioxide (B)</p> Signup and view all the answers

What type of organism uses oxygen only when it is present but can grow without it?

<p>Facultative anaerobe (C)</p> Signup and view all the answers

What is the best technique to use to measure the growth of filamentous organisms?

<p>Dry weight (D)</p> Signup and view all the answers

Which method is a statistical estimating technique used to determine the number of bacteria in a sample?

<p>Spread plate method (D)</p> Signup and view all the answers

Starting with one bacterial cell, how many cells would you have after 10 generations?

<p>1024 (B)</p> Signup and view all the answers

Which method is NOT suitable for determining the number of bacteria in a sample?

<p>Dry weight (A)</p> Signup and view all the answers

What is the primary limitation of using turbidity to estimate bacterial numbers?

<p>It overestimates bacterial numbers (C)</p> Signup and view all the answers

Which technique would be most suitable for quantifying bacteria that tend to form colonies and clumps?

<p>Direct microscopic count (A)</p> Signup and view all the answers

What characteristic makes the Most Probable Number method especially useful for low-density bacterial samples?

<p>Ability to estimate very low bacterial counts (A)</p> Signup and view all the answers

What is a potential drawback of using the Spread Plate method compared to direct counts for estimating bacterial numbers?

<p>Increased risk of contamination leading to inaccurate results (D)</p> Signup and view all the answers

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