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Microbiology > Chapter 7 EXAM III > Flashcards

Chapter 7 EXAM III Flashcards

1
Q

What are the ploidy’s of bacteria, archaea and eukaryotes?

A

bacteria and archaea are haploid, where eukaryotes are diploid.

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2
Q

How do most prokaryotes reproduce?

A

by binary fission, other reproduce by budding or fragmentation.

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3
Q

How does binary fission occur, generally?

A

a parent cell grows, elongates, replicates its genome, and then divides into two equal daughter cells.

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4
Q

What are the two major phases of the bacterial cell cycle?

A
  1. replication and partitioning DNA into progeny cells

2. Cytokinesis that separates the progeny cells.

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5
Q

How does replication begin in bacteria?

A

through a replisome at the origin of replication and ends at the terminus.

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6
Q

How is partitioning of the chromosome into the daughter cells aided?

A

by the MreB protein that is similar to eukaryotic actin.

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7
Q

How do plasmids replicate?

A

independently of the chromosome and cary genes specific for their segregation to daughter cells; ParR, an actin analog.

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8
Q

What is cytokinesis?

A

the process by which the parent cell is divided into two daughter cells; a tubulinlike protein (FtsZ) forms a dynamic Z ring that constricts to cause cell division.

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9
Q

How are the shapes of bacterial cells maintained?

A

by the cell wall. turgor pressure generated by cell osmolarity helps maintain cell shape and allows for expansion and growth.

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10
Q

Describe peptidoglycan synthesis.

A

NAG and NAM subunits are linked in the cell and moved across the plasma membrane with a lipid-soluble carrier; autolysins degrade existing peptidoglycan opening a place for expansion. Penicillin binding proteins are important to creating peptide cross links.

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11
Q

What determines the ultimate shape of the bacterial cell?

A

the pattern by which peptidoglycan units are added to the cell wall and the placement of cytoskeletal elements.

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12
Q

What are extremophiles?

A

microorganisms that grow under harsh conditions that would kill other organisms.

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13
Q

How do microorganisms protect themselves from dying in an environment with different solute concentrations?

A

inclusion bodies, mechanosensitive channels in the plasma membrane, rigid cell walls, compatible solutes, and contractile vacuoles.

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14
Q

What are osmoyolerant organisms?

A

those that can grow in solutions of both high and low water activity

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15
Q

What are halophiles?

A

organisms that require environments containing NaCl or otter salts above 0.2M.

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16
Q

what are extreme halophiles?

A

organisms that require more than 2 M NaCl for growth.

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17
Q

What is the water activity?

A

the amount of water available to microorganisms.

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18
Q

How is water activity reduced?

A

by the interaction of water with solute molecules.

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19
Q

What are acidophiles?

A

organisms that grow best between pH 0 and 5.5

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20
Q

What are neutrophiles?

A

organisms that grow best between pH 5.5 and 8.0

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21
Q

what are alkaliphiles?

A

organisms that grow best between pH 8.5 and 11.5

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22
Q

What are extreme alkaliphiles?

A

organisms that grow best at pH 10.0 or higher.

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23
Q

How can microorganisms adjust to changes in environmental pH?

A

by maintaining an internal pH that is near neutrality.

some bacteria synthesize protective proteins in response to pH.

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24
Q

What happens to the growth rate as the temperature rises?

A

there is an increase in the growth rate due to increasing rates of enzyme reaction; eventually a temperature becomes too high and microorganisms are damaged by protein denaturation, membrane disruption, and other phenomena.

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25
Q

What are the cardinal temperatures?

A

minimal, maximal and optimal.

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26
Q

What are psychrophiles?

A

organisms that can grow well at 0 degrees C, have optimal growth at 15 C or lower, an dusually will not grow above 20 C

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27
Q

what are psychotrophs?

A

can grow at 0 C, but have growth optima between 20 and 30 C, and growth maxima at about 35C

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28
Q

What are mesophiles?

A

have growth optima of 20 to 45C, minima of 15 to 20C and maxima of 45C or lower.

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29
Q

What are thermophiles?

A

have growth optima of 55 to 65C and minima around 45C

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30
Q

What are hyperthermophiles?

A

have growth optima of 85 to 113C and minima around 55C

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31
Q

What is an aerobe?

A

an organism able to grow in the presence of oxygen.

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32
Q

What is an anaerobe?

A

another that grows in the absence of oxygen.

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33
Q

Whatare obligate aerobes?

A

completely dependent on atmospheric oxygen for growth.

34
Q

What are facultative anaerobes?

A

do not require oxygen for growth, but grow better in its presence.

35
Q

What are aerotolerant anaerobes?

A

ignore oxygen and grow equally well whether it is present or not.

36
Q

what are obligate anaerobes?

A

do not tolerate oxygen and die in its presence.

37
Q

What are microaerophiles?

A

require lower oxygen levels (2 to 10%) for growth because normal atmospheric elves of oxygen (21%) are damaging to the cell.

38
Q

What are barotolerant organisms?

A

organisms that are adversely affected by increased pressure, but not as severely as are non tolerant organisms.

39
Q

What are piezophilic (basophilic) organisms?

A

require, or grow more rapidly in the presence of, increased pressure.

40
Q

Why is ionizing radiation harmful to microorganisms?

A

due to the high energy.
low levels produce mutations and may indirectly result in death, whereas high levels are directly lethal by direct damage to cellular macromolecules or through the production oxygen free radicals.

41
Q

How does ultraviolet radiation damage cells?

A

by causing the formation of thymine dimers in DNA; can be repaired by photo reactivation or by dark reactivation.

42
Q

What happens when visible light is too intense?

A

can cause formation of singlet oxygen, a highly reactive oxidizing agent.

43
Q

What are biofilms?

A

complex, slime-encased communities of microbes that form on surfaces; usually attached to something.

44
Q

What does biofilm formation involve?

A

cell deposition, attachment, replication and growth, excretion of extracellular polysaccharide matrix, maturation, and colonization of the biofilm.

45
Q

Why do biofilms pose a problem for bone implants and other medical devices?

A

because they are less sensitive to antibiotics.

46
Q

What is quorum sensing?

A

a process by which bacteria can communicate and behave cooperatively; may serve to sense population densities, determine diffusion rates of molecules secreted into the environment, and to regulate the expression of virulence factors.

47
Q

Describe signaling in bacteria.

A

gram-negative bacteria use acyl homoserine lactones as signals;
gram-positive bacteria often use oligopeptide signals.

48
Q

How is the protein structure stabilized when there is intense heat?

A

More hydrogen bonds.
more proline
more chaperones.
histone-like proteins stabilize DNA

49
Q

How is the membrane stabilized when there is intense heat?

A 
more saturated, more branched and higher molecular weight lipids
ether linkages (archaeal membranes)
50
Q

What kinds of enzymes do aerobes produce in order to protect themselves from the creates of superoxide radicals?

A

superoxide dismutase (SOD)
catalase
peroxidase

51
Q

What is inter domain communication?

A

communication between domains.

ex. Rhizobium interacting with a legume.

52
Q

What is synthetic media?

A

media in which all components and their concentrations are known.

53
Q

What is complex media?

A

media that contain some ingredients of unknown composition and or concentration.

54
Q

What are solidified media?

A

usually made with the addition of agar.

55
Q

What is supportive media?

A

general-purpose media for the growth of many microorganisms.

56
Q

what is enriched media

A

media supplemented by blood or other special nutrients to encourage the growth of fastidious heterotrophs.

57
Q

What is selective media?

A

favors the growth of particular microorganisms and inhibits the growth of others.

58
Q

what is differential media?

A

distinguishes between different groups of bacteria on the bases of their biological characteristics.

59
Q

What is anaerobic media?

A

contain reducing agents such as thioglycollate.

60
Q

How are anaerobic microbes cultured?

A

done inane anaerobic chamber, where oxygen has been eliminated.

61
Q

What is a pure culture?

A

a clonal population of cells arising from a single cell.

62
Q

What is a streak plate?

A

a method used to separate cells on the solid medium such that each colony arises from a single cell; an inoculating loop is used to streak microbes in a pattern that leads to their dilution.

63
Q

What is spread plate and pour plate?

A

the spread plate uses liquid culture to inoculate solid media and this is spread over the surface to separate the cells and produce clonal colonies; for pour plates, diluted liquid culture is mixed in cooled molten agar before being poured into culture dishes.

64
Q

What is the lag phase?

A

the period of apparent inactivity during which the cells are adapting to a new environment and preparing for reproductive growth, usually by synthesizing new cell components.

65
Q

What is the exponential phase?

A

the period during which the organisms are growing at the maximal rate possible given their genetic potential, the nature of the medium, and the condition under which they are growing; the population is the most uniform in terms of chemical and physical properties during this time.

66
Q

What is the stationary phase?

A

the number of viable microorganisms remains constant either because metabolically active cells stop reproducing or because the reproductive rate is balanced by the rate of cell death.

67
Q

what are some reasons that microbial populations enter a stationary phase?

A

starvation
toxic waste accumulation
cell density

68
Q

What are two alternative hypothesis for what occurs during the death phase?

A
  1. starved cells may enter a state called viable but nonculturable, a dormant state relieved by an appropriate change in environment.
  2. some cells in the population may undergo programmed cell death and their corpses used to feed the survivors .
69
Q

what is the mean growth rate constant?

A

the number of generations per unit time, often expressed as generations per hour.

70
Q

What is the mean generation time?

A

the time required for the number of cells in a population to double.

71
Q

How can direct counts of cells be made?

A

by direct microscopic observation on specially etched slides; does not distinguish between live and dea.

72
Q

What are membrane filters?

A

can be used to determine viable cell counts by staining with specific dyes or for direct cell counts of aquatic samples.

73
Q

What is flow cytometry?

A

detects cells in a thin stream by light scattering or fluorescent dyes

74
Q

What are coulter counters?

A

measure electric resistance as cells move through a small pore.

75
Q

what do viable cell counts require?

A

plating of diluted samples onto suitable growth media and monitoring colony formation.

76
Q

What is the most probable number?

A

analyses use liquid dilution tubes to statistically determine range densities for the initial culture; often uses selective media.

77
Q

When does measurement of cell mass become useful?

A

when a suitable parameter proportional to the number of microorganisms present is used.

78
Q

What are continuous culture methods?

A

used to maintain cells in the exponential growth phase at a constant biomass concentration for extended periods of time; these conditions are met by continual provision of nutrients and removal of wastes and biomass.

79
Q

What is a chemostat?

A

a continuous culture device that maintains a constant growth rate by supplying a medium containing a limited amount of an essential nutrient at a fixed rate and by removing medium that contains microorganisms at the same rate.

80
Q

What is a tubidostat?

A

a continuous culture device that regulate the flow rate of a medium through the vessel in order to maintain a predetermined turbidity or cell density; there is no limiting nutrient.

Microbiology (6 decks)

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