Microbiology Principles And Explorations 9th Edition by Jacquelyn G. Black -Test Bank A+

$35.00
Microbiology Principles And Explorations 9th Edition by Jacquelyn G. Black -Test Bank A+

Microbiology Principles And Explorations 9th Edition by Jacquelyn G. Black -Test Bank A+

$35.00
Microbiology Principles And Explorations 9th Edition by Jacquelyn G. Black -Test Bank A+

) Most bacteria reproduce by:

  1. a) sexual reproduction
  2. b) binary fission
  3. c) budding
  4. d) homologous recombination

Answer: b

Difficulty: Easy

Learning Objective 1: LO 6.1 Discuss what is meant by “growth” when referring to microbes and the ways in which it can be measured.

Section Reference 1: Section 6.1 Growth and Cell Division

2) The type of cell reproduction in which a small, new cell develops from the surface of an existing cell and then separates from the parent cell is known as ________ and is the normal mode of replication in _____ .

  1. a) binary fission, bacteria
  2. b) binary fission, yeast
  3. c) budding, bacteria
  4. d) budding, yeast

Answer: d

Difficulty: Easy

Learning Objective 1: LO 6.1 Discuss what is meant by “growth” when referring to microbes and the ways in which it can be measured.

Section Reference 1: Section 6.1 Growth and Cell Division

3) When a bacterial cell divides into two new cells, the new cells are called:

  1. a) daughter cells
  2. b) sister cells
  3. c) son cells
  4. d) father cells

Answer: a

Difficulty: Easy

Learning Objective 1: LO 6.1 Discuss what is meant by “growth” when referring to microbes and the ways in which it can be measured.

Section Reference 1: Section 6.1 Growth and Cell Division

4) Microbial growth:

  1. a) refers to the increase in the size of a microbial cell
  2. b) refers to the increase in the frequency of cell division
  3. c) in a single generation time leads to double the cell size
  4. d) in a single generation time leads to double the number of microbes.

Answer: d

Difficulty: Medium

Learning Objective 1: LO 6.1 Discuss what is meant by “growth” when referring to microbes and the ways in which it can be measured.

Section Reference 1: Section 6.1 Growth and Cell Division

5) Which of the following is not one of the phases of bacterial growth?

  1. a) Lag phase
  2. b) Stationary phase
  3. c) Doubling phase
  4. d) Log phase

Answer: c

Difficulty: Easy

Learning Objective 1: LO 6.1 Discuss what is meant by “growth” when referring to microbes and the ways in which it can be measured.

Section Reference 1: Section 6.1 Growth and Cell Division

6) A bacterial population grows most rapidly during ________ phase.

  1. a) lag
  2. b) log
  3. c) stationary
  4. d) death

Answer: b

Difficulty: Medium

Learning Objective 1: LO 6.1 Discuss what is meant by “growth” when referring to microbes and the ways in which it can be measured.

Section Reference 1: Section 6.1 Growth and Cell Division

7) In the stationary phase of bacterial growth:

  1. a) the number of newly generated cells is greater than the number of dying cells
  2. b) the number of newly generated cells is less than the number of dying cells
  3. c) the number of newly generated cells is the same as the number of dying cells
  4. d) none of the above

Answer: c

Difficulty: Medium

Learning Objective 1: LO 6.1 Discuss what is meant by “growth” when referring to microbes and the ways in which it can be measured.

Section Reference 1: Section 6.1 Growth and Cell Division

8) A bacterial culture can be kept in the log phase of growth indefinitely with the help of a/an:

  1. a) incubator
  2. b) chemostat
  3. c) spectrophotometer
  4. d) colony counter

Answer: b

Difficulty: Easy

Learning Objective 1: LO 6.1 Discuss what is meant by “growth” when referring to microbes and the ways in which it can be measured.

Section Reference 1: Section 6.1 Growth and Cell Division

9) Serial dilutions are used to:

  1. a) slow down the growth of microbes
  2. b) speed up the growth of microbes
  3. c) obtain bacterial cultures at several different concentrations
  4. d) form bacterial colonies

Answer: c

Difficulty: Easy

Learning Objective 1: LO 6.1 Discuss what is meant by “growth” when referring to microbes and the ways in which it can be measured.

Section Reference 1: Section 6.1 Growth and Cell Division

10) Which of the following counting techniques does not differentiate between live and dead bacterial cells in a culture?

  1. a) Serial dilution
  2. b) Spread plate
  3. c) Pour plate
  4. d) Direct microscopic count

Answer: d

Difficulty: Medium

Learning Objective 1: LO 6.1 Discuss what is meant by “growth” when referring to microbes and the ways in which it can be measured.

Section Reference 1: Section 6.1 Growth and Cell Division

11) Which of the following bacterial counting techniques relies on a statistical estimate to determine the number of bacteria in a culture?

  1. a) Serial dilution
  2. b) Standard plate count
  3. c) Spread plate
  4. d) Most probable number

Answer: d

Difficulty: Medium

Learning Objective 1: LO 6.1 Discuss what is meant by “growth” when referring to microbes and the ways in which it can be measured.

Section Reference 1: Section 6.1 Growth and Cell Division

12) Most bacteria:

  1. a) exhibit synchronous growth under natural conditions
  2. b) divide when a small new cell develops from the surface of an existing cell
  3. c) do not immediately increase in number when placed in a culture
  4. d) immediately begin to divide when placed in a culture

Answer: c

Difficulty: Medium

Learning Objective 1: LO 6.1 Discuss what is meant by “growth” when referring to microbes and the ways in which it can be measured.

Section Reference 1: Section 6.1 Growth and Cell Division

13) Bacterial growth in colonies on agar plates _____.

  1. a) have all phases of growth occurring simultaneously somewhere in the colony
  2. b) most growth occurs at the center of the colony
  3. c) involves budding of small new colonies from the surface of an existing colony
  4. d) have lag phase cells in the center of the colony, surrounded by a ring of cells in exponential phase

Answer: a

Difficulty: Medium

Learning Objective 1: LO 6.1 Discuss what is meant by “growth” when referring to microbes and the ways in which it can be measured.

Section Reference 1: Section 6.1 Growth and Cell Division

14) Turbidity in a bacterial culture can be measured using a/an:

  1. a) incubator
  2. b) colony counter
  3. c) spectrophotometer
  4. d) chemostat

Answer: c

Difficulty: Medium

Learning Objective 1: LO 6.1 Discuss what is meant by “growth” when referring to microbes and the ways in which it can be measured.

Section Reference 1: Section 6.1 Growth and Cell Division

15) Acidophiles would be expected to grow best at a pH of _____.

  1. a) 3
  2. b) 6
  3. c) 9
  4. d) 12

Answer: a

Difficulty: Easy

Learning Objective 1: LO 6.2 Review the physical and nutritional factors that can influence microbial growth.

Section Reference 1: Section 6.2 Factors Affecting Bacterial Growth

16) An obligate psychrophile would produce a turbid culture at ________ degrees Celsius.

  1. a) 15
  2. b) 30
  3. c) 45
  4. d) 60

Answer: a

Difficulty: Medium

Learning Objective 1: LO 6.2 Review the physical and nutritional factors that can influence microbial growth.

Section Reference 1: Section 6.2 Factors Affecting Bacterial Growth

17) Most human pathogens are _____.

  1. a) psychrophiles
  2. b) mesophiles
  3. c) thermophiles
  4. d) acidophiles

Answer: b

Difficulty: Easy

Learning Objective 1: LO 6.2 Review the physical and nutritional factors that can influence microbial growth.

Section Reference 1: Section 6.2 Factors Affecting Bacterial Growth

18) Which of the following is most likely to have evolved to live in the deep layers of mud, where there is a complete lack of free oxygen?

  1. a) Obligate aerobe
  2. b) Obligate anaerobe
  3. c) Facultative anaerobe
  4. d) Aerotolerant anaerobe

Answer: b

Difficulty: Medium

Learning Objective 1: LO 6.2 Review the physical and nutritional factors that can influence microbial growth.

Section Reference 1: Section 6.2 Factors Affecting Bacterial Growth

19) Which type of cell will generally shift to aerobic metabolism when oxygen is available but will carry on fermentation otherwise?

  1. a) aerotolerant anaerobes
  2. b) facultative anaerobes
  3. c) obligate anaerobes
  4. d) obligate aerobes

Answer: b

Difficulty: Easy

Learning Objective 1: LO 6.2 Review the physical and nutritional factors that can influence microbial growth.

Section Reference 1: Section 6.2 Factors Affecting Bacterial Growth

20) Capnophiles grow best under conditions of _____.

  1. a) high carbon dioxide
  2. b) low carbon dioxide
  3. c) high osmotic pressure
  4. d) low osmotic pressure

Answer: a

Difficulty: Medium

Learning Objective 1: LO 6.2 Review the physical and nutritional factors that can influence microbial growth.

Section Reference 1: Section 6.2 Factors Affecting Bacterial Growth

21) The toxic effects of the byproducts of oxygen metabolism are reduced by which of the following?

  1. a) Catalase
  2. b) Superoxide dismutase
  3. c) Lactase
  4. d) Two of the above

Answer: d

Difficulty: Medium

Learning Objective 1: LO 6.2 Review the physical and nutritional factors that can influence microbial growth.

Section Reference 1: Section 6.2 Factors Affecting Bacterial Growth

22) Where would you expect to find a barophile?

  1. a) At the bottom of the ocean
  2. b) In unpasteurized milk
  3. c) In the large intestine
  4. d) In sewage

Answer: a

Difficulty: Medium

Learning Objective 1: LO 6.2 Review the physical and nutritional factors that can influence microbial growth.

Section Reference 1: Section 6.2 Factors Affecting Bacterial Growth

23) When cells are placed in a hypertonic environment they will undergo ________ .

  1. a) lysis
  2. b) no change in size
  3. c) swelling of the cell which is contained by the cell wall
  4. d) plasmolysis

Answer: d

Difficulty: Medium

Learning Objective 1: LO 6.2 Review the physical and nutritional factors that can influence microbial growth.

Section Reference 1: Section 6.2 Factors Affecting Bacterial Growth

24) Halophiles require an environment with a high concentration of ________ for optimal growth.

  1. a) sugar
  2. b) alcohol
  3. c) salt
  4. d) phosphorous

Answer: c

Difficulty: Easy

Learning Objective 1: LO 6.2 Review the physical and nutritional factors that can influence microbial growth.

Section Reference 1: Section 6.2 Factors Affecting Bacterial Growth

25) Organisms with special nutritional needs are said to be _____.

  1. a) barophiles
  2. b) fastidious
  3. c) aerobes
  4. d) none of the above

Answer: b

Difficulty: Easy

Learning Objective 1: LO 6.2 Review the physical and nutritional factors that can influence microbial growth.

Section Reference 1: Section 6.2 Factors Affecting Bacterial Growth

26) Which of the following is considered a trace element?

  1. a) carbon
  2. b) zinc
  3. c) sulfur
  4. d) phosphorous

Answer: b

Difficulty: Medium

Learning Objective 1: LO 6.2 Review the physical and nutritional factors that can influence microbial growth.

Section Reference 1: Section 6.2 Factors Affecting Bacterial Growth

27) Starch would be broken down to maltose by which of the following exoenzymes?

  1. a) gelatinase
  2. b) amylase
  3. c) caseinase
  4. d) lipase

Answer: b

Difficulty: Medium

Learning Objective 1: LO 6.2 Review the physical and nutritional factors that can influence microbial growth.

Section Reference 1: Section 6.2 Factors Affecting Bacterial Growth

28) Which of the following statements about bacterial growth is false?

  1. a) Agar is used as a solidifying agent in some types of media.
  2. b) Bacteria growing in a liquid culture will generate colonies.
  3. c) A turbid culture is indicative of bacterial growth.
  4. d) Each bacterium plated will represent a colony-forming unit.

Answer: b

Difficulty: Medium

Learning Objective 1: LO 6.2 Review the physical and nutritional factors that can influence microbial growth.

Section Reference 1: Section 6.2 Factors Affecting Bacterial Growth

29) Exoenzymes:

  1. a) produced by Gram-positive rods act in the medium around the organism
  2. b) are released by the Golgi apparatus into the cytoplasm where they act
  3. c) produced by Gram-negative rods act in the periplasmic space
  4. d) two of the above

Answer: d

Difficulty: Hard

Learning Objective 1: LO 6.2 Review the physical and nutritional factors that can influence microbial growth.

Section Reference 1: Section 6.2 Factors Affecting Bacterial Growth

30) All of the following are ways microorganisms adapt to limited nutrients except:

  1. a) synthesize increased amount of enzymes for uptake and metabolism of limited nutrients
  2. b) form metabolically active highly resistant endospores
  3. c) synthesize enzymes needed to use a different nutrient source
  4. d) adjust the rate at which they metabolize nutrients

Answer: b

Difficulty: Hard

Learning Objective 1: LO 6.2 Review the physical and nutritional factors that can influence microbial growth.

Section Reference 1: Section 6.2 Factors Affecting Bacterial Growth

31) Sporulation occurs in:

  1. a) Clostridium
  2. b) Staphylocoocus
  3. c) Klebsiella
  4. d) Citrobacter

Answer: a

Difficulty: Easy

Learning Objective 1: LO 6.3 Examine the process of endospore formation and the advantages it provides to the bacteria capable of undergoing this process.

Section Reference 1: Section 6.3 Sporulation

32) Endospores are:

  1. a) metabolically active
  2. b) reproductive structures
  3. c) found mostly in Gram negative organisms
  4. d) protective structures

Answer: d

Difficulty: Easy

Learning Objective 1: LO 6.3 Examine the process of endospore formation and the advantages it provides to the bacteria capable of undergoing this process.

Section Reference 1: Section 6.3 Sporulation

33) Sporulation usually occurs in response to a/an _____.

  1. a) decrease in the level of carbon or nitrogen
  2. b) increase in temperature
  3. c) decrease in the amount of water
  4. d) increase in ultraviolet radiation

Answer: a

Difficulty: Medium

Learning Objective 1: LO 6.3 Examine the process of endospore formation and the advantages it provides to the bacteria capable of undergoing this process.

Section Reference 1: Section 6.3 Sporulation

34) A decrease in the amount of nitrogen to a culture of Clostridium botulinum would induce _____.

  1. a) activation
  2. b) germination
  3. c) sporulation
  4. d) outgrowth

Answer: c

Difficulty: Medium

Learning Objective 1: LO 6.3 Examine the process of endospore formation and the advantages it provides to the bacteria capable of undergoing this process.

Section Reference 1: Section 6.3 Sporulation

35) Within a bacterial endospore, the spore is most closely surrounded by the _____.

  1. a) spore membrane
  2. b) cortex
  3. c) cell membrane
  4. d) spore coat

Answer: a

Difficulty: Medium

Learning Objective 1: LO 6.3 Examine the process of endospore formation and the advantages it provides to the bacteria capable of undergoing this process.

Section Reference 1: Section 6.3 Sporulation

36) Which of the following does not contribute to endospore resistance to unfavorable conditions?

  1. a) Dipicolinic acid and calcium ions in the core
  2. b) Cortex
  3. c) Spore coat
  4. d) Germination proper

Answer: d

Difficulty: Medium

Learning Objective 1: LO 6.3 Examine the process of endospore formation and the advantages it provides to the bacteria capable of undergoing this process.

Section Reference 1: Section 6.3 Sporulation

37) Which of the following is not a stage in endospores returning to the vegetative state?

  1. a) Traumatic agent such as low pH or heat damages the coat.
  2. b) Outgrowth occurs in a medium with adequate nutrients.
  3. c) Divisions of the endospores early in their development.
  4. d) Water and nutrients penetrate damaged coat.

Answer: c

Difficulty: Hard

Learning Objective 1: LO 6.3 Examine the process of endospore formation and the advantages it provides to the bacteria capable of undergoing this process.

Section Reference 1: Section 6.3 Sporulation

38) A culture that contains only a single species of organism is known as a _____.

  1. a) pure culture
  2. b) Koch culture
  3. c) mixed culture
  4. d) contaminated culture

Answer: a

Difficulty: Easy

Learning Objective 1: LO 6.4 Compare the various types and purposes of culture media such as selective, enrichment, and differential media.

Section Reference 1: Section 6.4 Culturing Bacteria

39) The streak plate method produces pure cultures by separating individual bacterial cells from one another by _____.

  1. a) dragging them across a solid surface
  2. b) dispersing them in liquid media
  3. c) killing off those cells that are not able to survive in hot agar
  4. d) embedding some cells in the agar so that they are exposed to lower concentrations of oxygen

Answer: a

Difficulty: Easy

Learning Objective 1: LO 6.4 Compare the various types and purposes of culture media such as selective, enrichment, and differential media.

Section Reference 1: Section 6.4 Culturing Bacteria

40) The pour plate method of isolating pure cultures _____.

  1. a) relies on the fact that liquid agar will solidify as it cools
  2. b) is useful for growing microaerophiles
  3. c) results in some organisms growing embedded in the agar
  4. d) all of the above

Answer: d

Difficulty: Medium

Learning Objective 1: LO 6.4 Compare the various types and purposes of culture media such as selective, enrichment, and differential media.

Section Reference 1: Section 6.4 Culturing Bacteria

41) A growth medium consisting of only known amounts of water, magnesium, calcium chloride, potassium and glucose would be considered:

  1. a) a defined synthetic medium
  2. b) a complex medium
  3. c) a chemically nondefined medium
  4. d) two of the above

Answer: a

Difficulty: Easy

Learning Objective 1: LO 6.4 Compare the various types and purposes of culture media such as selective, enrichment, and differential media.

Section Reference 1: Section 6.4 Culturing Bacteria

42) A growth medium consisting of only water, glucose and beef extract would be considered _____.

  1. a) a defined synthetic medium
  2. b) a complex medium
  3. c) a chemically defined medium
  4. d) two of the above

Answer: b

Difficulty: Easy

Learning Objective 1: LO 6.4 Compare the various types and purposes of culture media such as selective, enrichment, and differential media.

Section Reference 1: Section 6.4 Culturing Bacteria

43) A media on which Gram-positive organisms turn green and Gram-negative organisms turn blue would be _____.

  1. a) selective
  2. b) differential
  3. c) complex
  4. d) enriched

Answer: b

Difficulty: Easy

Learning Objective 1: LO 6.4 Compare the various types and purposes of culture media such as selective, enrichment, and differential media.

Section Reference 1: Section 6.4 Culturing Bacteria

44) Sabourard’s agar has a low pH which encourages the growth of molds and discourages the growth of bacteria. Sabourard’s agar could best be described as being:

  1. a) selective
  2. b) differential
  3. c) complex
  4. d) enriched

Answer: a

Difficulty: Easy

Learning Objective 1: LO 6.4 Compare the various types and purposes of culture media such as selective, enrichment, and differential media.

Section Reference 1: Section 6.4 Culturing Bacteria

45) Bacteria that ferment lactose grow as red colonies on MacConkey’s agar while those that do not ferment lactose are transparent. MacConkey’s agar can best be described as being:

  1. a) selective
  2. b) differential
  3. c) complex
  4. d) enriched

Answer: b

Difficulty: Medium

Learning Objective 1: LO 6.4 Compare the various types and purposes of culture media such as selective, enrichment, and differential media.

Section Reference 1: Section 6.4 Culturing Bacteria

46) A candle jar would be used for growing:

  1. a) Gram-negative organisms
  2. b) fastidious organisms
  3. c) thermophiles
  4. d) microaerophiles

Answer: d

Difficulty: Medium

Learning Objective 1: LO 6.4 Compare the various types and purposes of culture media such as selective, enrichment, and differential media.

Section Reference 1: Section 6.4 Culturing Bacteria

47) A living, growing culture whose purpose is to maintain a pure culture of an organism indefinitely is a _____.

  1. a) colony
  2. b) stock culture
  3. c) sporulating culture
  4. d) broth culture

Answer: b

Difficulty: Easy

Learning Objective 1: LO 6.4 Compare the various types and purposes of culture media such as selective, enrichment, and differential media.

Section Reference 1: Section 6.4 Culturing Bacteria

48) Which of the following statements about liquid media and agar is false?

  1. a) Both chocolate agar and blood agar contain blood.
  2. b) Stock cultures are never directly used for laboratory studies.
  3. c) A differential media will allow some bacteria to grow and stop the growth of others.
  4. d) A selective media will suppress the growth of some microbes.

Answer: c

Difficulty: Medium

Learning Objective 1: LO 6.4 Compare the various types and purposes of culture media such as selective, enrichment, and differential media.

Section Reference 1: Section 6.4 Culturing Bacteria

49) Microaerophiles:

  1. a) grow best when the environment has a small amount of carbon dioxide.
  2. b) grow best when the environment has a small amount of free oxygen.
  3. c) need a high concentration of carbon dioxide.
  4. d) need a high concentration of oxygen.

Answer: b

Difficulty: Medium

Learning Objective 1: LO 6.4 Compare the various types and purposes of culture media such as selective, enrichment, and differential media.

Section Reference 1: Section 6.4 Culturing Bacteria

50) Chocolate agar:

  1. a) contains blood
  2. b) is used exclusively for stock cultures
  3. c) is nutrient poor
  4. d) is a selective agar plate

Answer: a

Difficulty: Medium

Learning Objective 1: LO 6.4 Compare the various types and purposes of culture media such as selective, enrichment, and differential media.

Section Reference 1: Section 6.4 Culturing Bacteria

51) ______ techniques must be strictly adhered to prevent the accidental contamination of stock cultures.

  1. a) Germination
  2. b) Selective
  3. c) Differential
  4. d) Aseptic

Answer: d

Difficulty: Medium

Learning Objective 1: LO 6.4 Compare the various types and purposes of culture media such as selective, enrichment, and differential media.

Section Reference 1: Section 6.4 Culturing Bacteria

52) Nonculturable organisms:

  1. a) are rare.
  2. b) can be identified based on their DNA.
  3. c) can only be seen on selective agar plates.
  4. d) have defined generation times.

Answer: b

Difficulty: Medium

Learning Objective 1: LO 6.4 Compare the various types and purposes of culture media such as selective, enrichment, and differential media.

Section Reference 1: Section 6.5 Living, But Nonculturable, Organisms

53) During this phase, organisms produce large amounts of ATP.

  1. a) A
  2. b) B
  3. c) C
  4. d) D

Answer: a

Difficulty: Easy

Learning Objective 1: LO 6.1 Discuss what is meant by “growth” when referring to microbes and the ways in which it can be measured.

Section Reference 1: Section 6.1 Growth and Cell Division

54) This phase decreases at a logarithmic rate.

  1. a) A
  2. b) B
  3. c) C
  4. d) D

Answer: d

Difficulty: Easy

Learning Objective 1: LO 6.1 Discuss what is meant by “growth” when referring to microbes and the ways in which it can be measured.

Section Reference 1: Section 6.1 Growth and Cell Division

55) Microbes that live in this environment actively transport _____ out of their cells.

  1. a) potassium
  2. b) oxygen
  3. c) sodium
  4. d) nitrogen

Answer: c

Difficulty: Easy

Learning Objective 1: LO 6.2 Review the physical and nutritional factors that can influence microbial growth.

Section Reference 1: Section 6.2 Factors Affecting Bacterial Growth

Question Type: Essay

56) Draw and label a standard growth curve. Describe each of the 4 phases. Why do you think bacteria do not continue to double indefinitely? You sample a culture that has reached the fourth phase after 2 days, can you think of one reason why the culture would begin to increase on day 4?

Answer: Growth curve should have a flat lag phase, followed by an upward sloping log phase, then a flat stationary phase and lastly a downward sloping decline or death phase. The four phases are : 1) lag phase -the organisms are metabolically active synthesizing DNA and enzymes but not increasing in number; 2) log phase organisms are dividing exponentially; 3) stationary phase -number of new cells produced equals number of cells dying; 4) decline phase -where many cells have lost their ability to divide and are dying due to toxin buildup and nutrient deprivation.

Bacteria cannot increase exponentially forever as the amount of nutrients will always eventually be consumed or limited. Also toxic byproducts of metabolism would eventually build up.

One reason for the culture to increase again on day 4 is scavenging; in this case the dying cells release their cell components as nutrients that the remaining cells can use to grow. Another could be the production of spores. Or there could be a mutation that arises that allows the bacteria to grow on a new nutrient.

Difficulty: Medium

Learning Objective 1: LO 6.1 Discuss what is meant by “growth” when referring to microbes and the ways in which it can be measured.

Section Reference 1: Section 6.1 Growth and Cell Division

57) What is sporulation? What triggers sporulation? In bacteria that form endospores generally only a fraction of the total population sporulate and the process takes over eight hours. Explain why it would be harmful for the whole population to sporulate. Is it better to continuously form spores or wait to sporulate when conditions become unfavorable?

Answer: Sporulation is the formation of endospores which are not metabolically active and are very resistant to extreme conditions and stress. The endospore cannot divide but can wake up when conditions for growth are restored. Endospores are generally triggered during stationary phase in response to environmental, metabolic and cell cycle signals.

It would be harmful for the whole population to sporulate if the conditions changed rapidly or not predictably, if for example within those eight hours the nutrients where restored then the whole population would be unable to respond as they would still be sporulating. Also if there were a false alarm it would also be harmful for the whole population to sporulate.

An advantage to continuously forming spores are mainly in rapidly changing or unpredictable conditions as there will always be a safety net (spores) already formed. A disadvantage to continuously forming spores is that spores are not dividing, therefore they do not contribute to increasing the size of the bacteria population (e.g., fitness) and could be seen as diverted resource.

Difficulty: Hard

Learning Objective 1: LO 6.3 Examine the process of endospore formation and the advantages it provides to the bacteria capable of undergoing this process.

Section Reference 1: Section 6.3 Sporulation

58) Imagine NASA sends you a specimen from a planet that they believe contains an extraterrestial bacterial species. You are the microbiologist in charge of determining how to grow the extraterrestial bacteria. Many factors may affect the growth of extraterrestial bacteria. Choose two and describe how you would test their effects.

Answer: Physical factors that could affect the growth of this extraterrestial bacterium (along with how to test them in parenthesizes) include: acidity and alkalinity (grow along range of pH broths), temperature (grow along a temperature range), quantity of oxygen and perhaps other gases in the environment (grow in incubators with different quantities of oxygen or in bell jars or observe where the pattern of growth is in nutrient broth), moisture (try a range of humidities), hydrostatic or osmotic or gravitational pressure (try a range of pressures), radiation (try irradiating the bacteria).

Nutritional factors that could affect the growth of this extraterrestial bacterium (to test them one would simply vary the concentration or quality of the nutrients in the broth) include: carbon sources, nitrogen sources, sulfur, phosphorus, trace elements and vitamins. In addition growth could depend on the nutritional complexity (to test would need to vary complexity of broths).

Difficulty: Easy

Learning Objective 1: LO 6.2 Review the physical and nutritional factors that can influence microbial growth.

Section Reference 1: Section 6.2 Factors Affecting Bacterial Growth

+
-
Only 0 units of this product remain

You might also be interested in