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Biology 228: Microbiology > Chapter 9 > Flashcards

Chapter 9 Flashcards

1
Q

What kind of reproduction occurs in prokaryotes?

A

Asexual

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2
Q

How does DNA replication occur before binary fission?

A

The cell grows and DNA replication starts at a location on the circular chromosome called the origin of replication. Replication continues in both directions until two chromosomes are established.

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3
Q

What is FtsZ?

A

A protein that directs the cytokinesis and cell division for binary fission.

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4
Q

What is a Z ring?

A

FtsZ assembles into a Z ring on the cytoplasmic membrane. The Z ring is anchored by FtsZ-binding proteins and defines the division plane between the two daughter cells.

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5
Q

What occurs after the Z ring has defined the division?

A

Additional proteins required for cell division are added to the Z ring to form the divisome. The divisome activates to produce a peptidoglycan cell wall and build a septum that divides the two daughter cells. The daughter cells are separated by the division septum, where all of the cells’ outer layers must be remodeled to complete division.

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6
Q

What is generation time (doubling time)?

A

The time it takes for the population to double through one round of binary fission.

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7
Q

What is cultural density?

A

The number of cells per unit volume.

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8
Q

What are the four phases of the growth curve?

A

-Lag phase
-Log phase
-Stationary phase
-Death or decline phase

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9
Q

What is the Lag phase?

A

No increase in number of bacterial cells.

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10
Q

What is the Log phase?

A

Exponential increase in number of living bacterial cells.

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11
Q

What is the stationary phase?

A

Plateau in number of living bacterial cells; rate of cell division and death are roughly equal.

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12
Q

What is the death or decline phase?

A

Exponential decrease in number of living bacterial cells.

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13
Q

What is the intrinsic growth rate?

A

The generation time under specific growth conditions is genetically determined.

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14
Q

How can cells be counted?

A
  • Direct viable cell count (microscopic or plate)
  • Serial dilutions
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15
Q

What are serial dilutions?

A

The pour plate and spread plate methods are used to plate into or onto, respectively, agar to allow counting of viable cells that give rise to colony-forming units (diluted each time placed on a plate).

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16
Q

What is the most probable number (MPN) method?

A

A statistical procedure for estimating the number of viable microorganisms in a sample.

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17
Q

What are the indirect methods of counting cells?

A

Measuring turbidity or measuring dry weight of a culture sample or measuring metabolic activity.

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18
Q

What does turbidity mean?

A

The cloudiness of a sample of bacteria in a liquid suspension.

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19
Q

What can be used to measure turbidity?

A

A spectrophotometer which measures how much light can pass through the solution.

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20
Q

What are the other methods of cell division that prokaryotes could use?

A

Asymmetrical division (budding) or production of spores in aerial filaments or fragmentation (a new cell splits from the parent filament and floats away).

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21
Q

What are biofilms?

A

Biofilms are complex and dynamic ecosystems that form on a variety of environmental surfaces. Ex. inside mouth
- highly structured communities that provide a selective advantage to their constituent microorganisms

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22
Q

How do environmental conditions influence the overall structure of biofilms?

A

The form structures to give them an advantage in their select environment.

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23
Q

How is the extracellular matrix related to the biofilm?

A

Consists of extracellular polymeric substances (EPS) secreted by the organisms in the biofilm which plays a key role in maintaining the integrity and function of the biofilm. The extracellular matrix represents a large fraction of the biofilm, accounting for 50%–90% of the total dry mass.

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24
Q

What is the EPS important for?

A

Channels in the EPS allow movement of nutrients, waste, and gases throughout the biofilm. This keeps the cells hydrated, preventing desiccation. EPS also shelters organisms in the biofilm from predation by other microbes or cells (e.g., protozoans, white blood cells in the human body).

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25
Q

How do biofilms form?

A

The formation of a biofilm occurs when planktonic cells attach to a substrate and become sessile.

26
Q

What are the five stages of biofilm formation?

A
  1. Reversible attachment of planktonic cells.
  2. First colonizers become irreversibly attached.
  3. Growth and cell division.
  4. Production of EPS and formation of water channels.
  5. Attachment of secondary colonizers and dispersion of microbes to new sites.
27
Q

What is quorum sensing?

A

The mechanism by which cells in a biofilm coordinate their activities in response to environmental stimuli.

28
Q

What do autoinducers do?

A

Enables microorganisms to detect their cell density through the release and binding of small, diffusible molecules (autoinducers).
- Autoinducers signal the start and stop of quorum sensing

29
Q

How do biofilms connect to the human body?

A

they can be beneficial (ex. ward off infections) or harmful (ex. cause dental disease)

30
Q

What is the relationship between pathogens and biofilms?

A

Pathogens embedded within biofilms exhibit a higher resistance to antibiotics than their free-floating counterparts.

31
Q

What is used to determine oxygen requirements?

A

Thioglycolate tubes

32
Q

What are obligate (strict) aerobes? Where would they grow in a tube of broth?

A

They cannot grow without an abundant supply of oxygen.
- They would grow at the top of the tube where there is oxygen

33
Q

What are obligate (strict) anaerobes? Where would they grow in a tube of broth?

A

They are killed by oxygen.
- At the very bottom of the tube where there is no oxygen

34
Q

What are facultative anaerobes? Where would they grow in a tube of broth?

A

Organisms that thrive in the presence of oxygen but also grow in its absence.
- Heavy growth at the top of the tube and growth throughout the tube

35
Q

What are aerotolerant anaerobes? Where would they grow in a tube of broth?

A

They are indifferent to the presence of oxygen.
- They grow all over the tube

36
Q

What are microaerophiles? Where would they grow in a tube of broth?

A

Bacteria that require a minimum level of oxygen for growth, about 1%–10%.
- The colony would sit in a group in the tube where there is the correct percent of oxygen

37
Q

What is optimum oxygen concentration?

A

The ideal concentration of oxygen for a particular microorganism.

38
Q

What does ROS stand for?

A

Reactive oxygen species

39
Q

What kind of species have ROS?

A

It is generated by aerobic respiration.
Anaerobic respiration still needs to be able to tackle this in the atmosphere.

40
Q

What are some enzymes that break down the toxic byproduct ROS?

A

Peroxidase, Catalase, Superoxide Dismutase

41
Q

What is a capnophile?

A

An organism that requires a higher than atmospheric concentration of CO2.

42
Q

What are optimum growth pH? maximum growth pH? and minimum growth pH?

A

Optimum growth pH is the most favorable pH for the growth of an organism.
The lowest pH value that an organism can tolerate is called the minimum growth pH.
The highest pH is the maximum growth pH.

43
Q

What type of bacteria grow optimally at pH 7?

A

Neutrophiles

44
Q

What type of bacteria grow optimally at a pH of less than 5.55?

A

Acidophiles

45
Q

What type of bacteria grow optimally at a pH between 8 and 10.5?

A

Alkaliphiles

46
Q

Which type of pH related bacteria is most common?

A

Neutrophiles

47
Q

What organisms have an optimal growth range between 20°C and 45°C?

A

Mesophiles

48
Q

What organisms have an optimal growth range between 4°C and 25°C?

A

Psychrotrophs

49
Q

What organisms have an optimal growth range between 0°C and 15°C?

A

Psychrophiles

50
Q

What organisms have an optimal growth range between 50°C and 80°C?

A

Thermophiles

51
Q

What organisms have an optimal growth range between 80°C and 110°C?

A

Hyperthermophiles

52
Q

What do adaptations to different temperatures require?

A

Changes in the composition of membrane lipids and proteins.

53
Q

What are halophiles?

A

Require high concentration of salt for growth.

54
Q

What are halotolerant organisms?

A

Organisms that can grow and multiply in the presence of high salt but do not require it for growth.

55
Q

What are barophiles?

A

Microorganisms that require high atmospheric pressure for growth.

56
Q

What do light and moisture have to do with growth?

A
  • Photosynthetic bacteria depend on visible light for energy.
  • Most bacteria, with few exceptions, require high moisture to grow
57
Q

What is enriched media?

A

Enriched media, contains growth factors, vitamins, and other essential nutrients to promote the growth of fastidious organisms, organisms that cannot make certain nutrients and require them to be added to the medium.

58
Q

What is chemically defined media?

A

When the complete chemical composition of a medium is known.

59
Q

What is a complex media?

A

The precise chemical composition of the medium is not known.

60
Q

What is selective media?

A

Media that inhibit the growth of unwanted microorganisms and support the growth of the organism of interest by supplying nutrients and reducing competition.

61
Q

What is differential media?

A

Make it easy to distinguish colonies of different bacteria by a change in the color of the colonies or the color of the medium.
- Color changes are the result of end products created by interaction of bacterial enzymes with differential substrates in the medium or, in the case of hemolytic reactions, the lysis of red blood cells in the medium.

Biology 228: Microbiology (20 decks)

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