Microorganisms and Bacterial Growth Quiz

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Questions and Answers

What is the mean division time for the bacteria in population A as stated in the example?

  • 20 minutes (correct)
  • 30 minutes
  • 60 minutes
  • 10 minutes

How many times will one bacterium divide in six hours if it has a division time of 20 minutes?

  • 18 times (correct)
  • 12 times
  • 30 times
  • 15 times

In the context of bacterial growth, what does each division of a bacterium result in?

  • Tripling the number of bacteria
  • No change in the number of bacteria
  • Halving the number of bacteria
  • Doubling the number of bacteria (correct)

What is the final calculation of bacteria after six hours, starting with one bacterium and dividing 18 times?

<p>262,144 bacteria (B)</p> Signup and view all the answers

What are exponents also referred to as?

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

Which phase of the bacterial growth curve indicates that bacteria are metabolically active but not dividing?

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

What mathematical operation is used to express the final population of 262,144 in standard form?

<p>Use of powers of 10 (C)</p> Signup and view all the answers

What does the term 'division time' refer to in bacterial growth?

<p>The duration from one division to the next (B)</p> Signup and view all the answers

What occurs during the lag phase of bacterial growth?

<p>Cells increase in size but do not divide. (C)</p> Signup and view all the answers

Which phase of bacterial growth is characterized by the highest rate of cell division?

<p>Exponential (Log) Phase (C)</p> Signup and view all the answers

What primarily happens during the stationary phase of bacterial growth?

<p>The number of dying cells equals the number of dividing cells. (D)</p> Signup and view all the answers

During which phase are antibiotics most effective against bacterial cells?

<p>Exponential (Log) Phase (D)</p> Signup and view all the answers

What are virulence factors and when are they generated?

<p>They help pathogenic bacteria survive harsh conditions in the stationary phase. (C)</p> Signup and view all the answers

What happens to the population of bacteria during the death phase?

<p>The number of living cells decreases exponentially. (C)</p> Signup and view all the answers

What is a common characteristic of the exponential (log) phase?

<p>High metabolic activity with cell division. (C)</p> Signup and view all the answers

What typically occurs as waste products accumulate in a bacterial culture?

<p>Growth may decline and lead to the death phase. (C)</p> Signup and view all the answers

What is the optimal pH range for alkaliphiles?

<p>8 to 10 (B)</p> Signup and view all the answers

Which term describes bacteria that grow best in moderate temperatures?

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

Which type of bacteria can survive in temperatures below 0°C?

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

What type of bacteria are cyanobacteria classified as?

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

What distinguishes purple and green bacteria from other photosynthetic bacteria?

<p>They use sulfide or sulfur for photosynthesis. (B)</p> Signup and view all the answers

At what temperature range do thermophiles thrive?

<p>50°C to 80°C (A)</p> Signup and view all the answers

Which type of bacteria is most likely to be found in arctic lakes?

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

What is the role of the enzyme secreted by certain bacteria in the stomach?

<p>To neutralize stomach acid (B)</p> Signup and view all the answers

What is the role of dying cells in the bacterial life cycle?

<p>They cause spore production in nearby bacteria. (C)</p> Signup and view all the answers

Which type of bacteria requires oxygen for survival?

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

What type of bacteria can grow in low oxygen concentrations but requires oxygen?

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

Which of the following best describes acidophiles?

<p>Bacteria that thrive in acidic environments below pH 5. (B)</p> Signup and view all the answers

What is the optimal pH level for neutrophiles?

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

What metabolic process do facultative anaerobes utilize in oxygen-deprived environments?

<p>Anaerobic respiration (D)</p> Signup and view all the answers

Which bacteria type does NOT rely on oxygen and can survive its presence?

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

Campylobacter jejuni is classified as which type of bacteria based on its oxygen requirement?

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

Flashcards

Bacterial Division Time

The time interval between successive divisions of a bacterium.

Calculating Bacterial Growth

Using the number of divisions and initial bacteria count to find the final population.

Bacterial Growth Curve

Graphical representation of the number of living bacteria in a population over time.

Lag Phase

Initial phase of bacterial growth where bacteria are active but not dividing.

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Exponential Growth (Log Phase)

Phase of rapid bacterial reproduction, doubling in population size.

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Stationary Phase

Phase of bacterial growth where the number of new bacteria equals the number of dead bacteria.

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Death Phase

Phase where bacteria die off at a faster rate than they reproduce.

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Exponent

How many times a number is used in multiplication.

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Exponential (Log) Phase

Phase of rapid bacterial growth where cells divide rapidly, doubling in number.

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Binary Fission

A type of asexual reproduction where a single cell divides into two identical cells.

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Optimal Conditions

Laboratory environment allowing for ideal bacterial growth.

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Nutrient Rich Medium

A medium providing essential substances required for bacterial growth.

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Obligate aerobes

Bacteria that need oxygen to survive and grow

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Obligate anaerobes

Bacteria that can't survive in the presence of oxygen

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Facultative anaerobes

Bacteria that can grow with or without oxygen

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Aerotolerant anaerobes

Bacteria that don't use oxygen but aren't harmed by it

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Microaerophilic bacteria

Bacteria that need oxygen at low concentrations

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Acidophiles

Bacteria that thrive in acidic environments (pH < 5)

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Neutrophiles

Bacteria that thrive in neutral environments (pH near 7)

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Bacterial death phase

A stage in bacterial growth where cells die and release nutrients

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Alkaliphiles

Bacteria that thrive in basic environments with pH levels between 8 and 10, such as alkaline soils and lakes.

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Psychrophiles

Bacteria that grow best in cold environments (4°C to 25°C), found in places like arctic lakes and deep oceans.

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Mesophiles

Bacteria that thrive in moderate temperatures (20-45°C), including those in the human microbiome.

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Thermophiles

Bacteria that grow best in hot environments (50-80°C), often found in hot springs and geothermal soils.

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Hyperthermophiles

Bacteria that favor extremely hot temperatures (80°C-110°C), such as those found in volcanic vents.

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Photoautotrophs

Bacteria that use light energy for photosynthesis, like cyanobacteria.

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Cyanobacteria

Photosynthetic bacteria with chlorophyll, producing oxygen and living in various environments, including water and lichens.

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Bacteriochlorophyll

Pigment found in purple and green bacteria, absorbing shorter wavelengths of light than chlorophyll.

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Study Notes

Micro-Organisms and Applications

  • Handling microorganisms safely requires specific techniques
  • Studying microorganisms provides vital information about their growth and uses

Bacterial Growth

  • Bacteria reproduce at regular intervals (e.g., every 20 minutes)
  • This allows predictions of bacterial population size over time

Calculating Bacterial Population

  • Example: Mean division time for bacteria population A is 20 minutes, starting with one bacterium. Calculate population after six hours.
  • Part 1: Calculate the number of divisions. (60 minutes/20minutes per division) x 6 hours = 18 divisions
  • Part 2: Calculate the final population. Initial population (1) x 2^(number of divisions) = 262,144 bacteria
  • Population size doubles with each division
  • Results can also be expressed in scientific notation

Logarithms

  • Logarithms are in the form logax
  • log525 means "What power of 5 gives 25?"
  • Answer is 2 because 52 = 25 (log525 = 2)

Exponents

  • Exponents indicate the number of times a number is used in multiplication
  • In 82, the "2" indicates using 8 twice in multiplication (8 x 8 = 64)

Phases of Bacterial Growth Cycle

  • The bacterial growth curve represents the number of live cells over time
  • Four phases: lag, exponential, stationary, and death
  • Lag Phase: Active but not dividing
  • Exponential Phase: Cells divide rapidly by binary fission. High metabolic activity.
  • Stationary Phase: Growth slows; dividing cells equal dying cells.
  • Death Phase: Nutrients run out, waste products increase; number of dying cells rise rapidly

Bacterial Growth and Oxygen

  • Bacteria require an environment suitable for their growth (oxygen, pH, temperature, light)
  • Obligate aerobes: Require oxygen
  • Obligate anaerobes: Cannot survive in the presence of oxygen
  • Facultative anaerobes: Can grow with or without oxygen
  • Aerotolerant anaerobes: Not harmed by oxygen, but can only function without it
  • Microaerophiles: Need limited oxygen

Bacterial Growth and pH

  • Bacteria thrive in specific pH ranges
  • Acidophiles: Thrive in acidic environments (pH < 5)
  • Neutrophiles: Thrive in neutral environments (pH near 7)
  • Alkaliphiles: Thrive in basic environments (pH 8-10)

Bacterial Growth and Temperature

  • Psychrophiles: Thrive in cold temperatures (4-25°C)
  • Mesophiles: Thrive in moderate temperatures (20-45°C)
  • Thermophiles: Thrive in hot temperatures (50-80°C)
  • Hyperthermophiles: Thrive in extremely hot temperatures (80-110°C)

Bacterial Growth and Light

  • Some bacteria require light for growth
  • Photoautotrophs (e.g., Cyanobacteria): Use light energy for photosynthesis and produce oxygen
  • Other bacteria: Use light energy for photosynthesis but don't produce oxygen, using sulfur or sulfide. (e.g., purple and green bacteria)

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