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Micro BIO 220 Part 1 > Lecture 4 > Flashcards

Lecture 4 Flashcards

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1
Q

What is the difference between a macronutrient and micronutrient?

A

Macronutrient are those required in relatively large quantity. Micronutrient are those required in small amounts. C, O,N, H,P are macronutrients

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2
Q

What are the three most abundant elements in a bacterial cell as a percentage of dry weight?

A

carbon, oxygen, nitrogen

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3
Q

What are essential nutrients?

A

carbon, hydrogen, oxygen, phosphate, sulfur, (CHONPS), They are macronutrients

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4
Q

What are some examples of roles of the essential nutrients C, N, P, and S?

A

C: among the common organic molecules that can satisfy the requirement are proteins, carbs, lipids, and nucleic acids
N:makes up 79% of the earth atmos.
P: found in rocks and mineral deposits, key component of nucleic acids, serves cellular energy
S: mineral form, rocks and sediments, vitamins,

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5
Q

What are some examples of inorganic and organic nutrients?

A

Inorganic: O2 and CO2 gas; ammonia or nitrate
Organic:Methane, acetate
Glucose, amino acids
Macromolecules like proteins, lipids, carbohydrate polymers (e.g. starch)

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6
Q

What molecule makes up the majority of the total mass of a typical bacterial cell?

A

Cells are mostly water: ~70% of cellular mass

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7
Q

What are the major components of a typical bacterial cell by dry mass?

A

Elements CHONPS – 96% of dry cell weight
Organic compounds – 97% of dry cell weight
~50% dry weight is protein
-they are macromolecules ?

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8
Q

• What is the relative abundance of protein, RNA, DNA, carbohydrates, and lipids in a typical bacterial cell?

A

RNA:20
DNA:3
Carbs: 10
Lipids:10

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9
Q

How does this relate to the abundance of C, O, H and N atoms in cells (i.e. compare the left and right columns in Table 6.1 in your book).

A

no

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10
Q

• What is the difference between a complex medium and a defined medium?

A

In a defined medium, all individual chemical components are present in known quantities

In a complex medium, exact concentrations of some components are not known, often because they are extracts from other organisms

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11
Q

Between a rich and a minimal medium?

A

A rich medium has a variety of different growth substrates

A minimal medium only a single or a few substrates

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12
Q

Are not mutually exclusive categories, e.g. can a rich medium also be a defined medium?

A

yes

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13
Q

What distinguishes photoautotrophs?

A

Can gain energy from light (photons)

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14
Q

What distinguishes Heterotroph?

A

must obtain its carbon in an organic form

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15
Q

What distinguishes Autotroph: ?

A

Use inorganic C as its carbon source (e.g. CO2)

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16
Q

What distinguishes Chemotroph?

A

Gain energy from chemical compounds

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17
Q

In which of these categories do most pathogenic microbes fall?

A

Chemoheterotrophs

Saprobes and parasites are specific types of chemoheterotrophs

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18
Q

What is osmosis?

A

The diffusion of water through a selectively, or differentially, permeable membrane

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19
Q

Can water pass (relatively) freely across a cytoplasmic membrane?

A

Yes through Simple diffusion,

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20
Q

In which of these might a cell rupture due to osmotic lysis if it lacks a cell wall (or has a weakened cell wall)?

A

Hypotonic conditions

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21
Q

What is the major difference between passive and active transport?

A

Passive transport: mechanisms that do not require energy

Active transport: mechanisms that do require energy

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22
Q

What are two energy sources that might be used to power active transport?

A

Energy source can be ATP or proton motive force (PMF)

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23
Q

What is an example of active transport that only occurs in eukaryotes?

A 
Endocytosis: “eating or drinking” by eukaryotic cells
Bulk transport of solid particles or liquid droplets
Requires energy (form of active transport) and ability to perform endocytosis
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24
Q

During which stages of growth of a batch culture would you expect the turbidity to be the lowest and the highest?

A

Cultures have lowest turbidity just after inoculation (lag phase), then increase during exponential
phase, and have highest
turbidity in stationary phase

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25
Q

What is a plaque assay, and what type of microbe is this used to grow?

A

The plaque assay can be used to purify a clonal population of virus or to determine viral titer as plaque-forming units per ml (pfu/ml) so that known amounts of virus can be used to infect cells during subsequent work.

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26
Q

What “ingredients” are necessary for performing a plaque assay?

A

soft agar overlay

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27
Q

What is a plaque forming unit (PFU)?

A

In virology, a plaque-forming unit (PFU) is a measure of the number of particles capable of forming plaques per unit volume, such as virus particles.

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28
Q

Isotonic conditions

A

Extracellular solute concentration is equal to the cell’s internal environment
Diffusion of water proceeds at the same rate in both directions
No net change in cell volume
The most stable environments for cells because they are already in a steady state (equilibrium) with their environment

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29
Q

Hypotonic conditions

A

Solute concentration of the external environment is lower than that of the cell’s internal environment
Pure water is the most hypotonic environment, because it has no solute
Net direction of osmosis is from the hypotonic solution into the cell
Cells without cell walls swell and burst

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30
Q

Hypertonic conditions

A

The environment has a higher solute concentration than the cytoplasm
High osmotic pressure forces water to diffuse out of the cell
Cell cytoplasm shrinks
Highly hypertonic conditions can impair growth

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31
Q

Isotonic solution

A

Water concentration is equal inside
and outside the cell, thus rates of
diffusion are equal in both directions

Rates of diffusion are equal in
both directions.

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32
Q

Hypotonic solution

A

Net diffusion of water is into the cell; this
swells the protoplast and pushes it tightly
against the wall; wall usually prevents
cell from bursting.

Diffusion of water into the cell causes
it to swell, and may burst it if no
mechanism exists to remove the water

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33
Q

Hypertonic solution

A

Water diffuses out of the cell and
shrinks the cell membrane away from
the cell wall; process is known as
plasmolysis.

Water diffusing out of the cell causes
it to shrink and become distorted.

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34
Q

Passive transport:

A

mechanisms that do not require energy.
Substrate transport from high to low concentrations only.
1) Simple diffusion
Directly through cytoplasmic membrane
2) Facilitated diffusion
Mediated by transport proteins in the membrane

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35
Q

Active transport

A

mechanisms that do require energy
Transport from low to high concentrations, against concentration gradient.
Mediated by specific transport proteins in the membrane
1) Carrier mediated active transport
Energy source can be ATP or proton motive force (PMF)
2) Group translocation
Energy source is typically ATP
3) Bulk transport or endocytosis, see below
Energy source is typically ATP

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36
Q

Endocytosis:

A

“eating or drinking” by eukaryotic cells
Bulk transport of solid particles or liquid droplets
Requires energy (form of active transport) and ability to perform endocytosis
Only in Eukaryotes

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37
Q

For prokaryotes, macromolecules are usually

A

broken down by secreted, extracellular enzymes prior to transport.

38
Q

Endocytosis: “eating or drinking” by eukaryotic cells Called phagocytosis

A

if a solid is transported

39
Q

Endocytosis: “eating or drinking” by eukaryotic cells Called pinocytosis

A

if a liquid is transported

40
Q

what are Environmental Factors That Influence Microbes?

A

The function of metabolic enzymes
The stability of membranes
Transport and activity of nutrients (e.g. pH affecting charge)

Survival in a changing environment is largely a matter of whether microorganisms can adapt to alterations in their habitat

41
Q

large groups of microbes can indeed have large affects on their

A

local environment

42
Q

Cardinal temperatures?

A

Three temperatures that summarize how temperature limits growth of a given microbe

43
Q

Minimum temperature ?

A

the lowest temperature that permits a microbe’s continued growth and metabolism; below this temperature, its activities are limited (protein function, membrane fluidity)

44
Q

Optimum temperature ?

A

an intermediate between the minimum and the maximum which promotes the fastest rate of growth and metabolism

45
Q

Maximum temperature?

A

the highest temperature at which growth and metabolism can proceed, often due to denaturation (unfolding) of key proteins and/or membrane loses integrity

46
Q

Psychrophilic (psychrophiles)

A

Optimum temperature below 15°C; cannot grow above 20°C
Natural habitats include lakes, rivers, snowfields, polar ice, and the deep ocean
Rarely pathogenic

47
Q

Psychrotrophic (psychrotrophs)

A

Have an optimum temperature between 15°C and 30°C
Staphylococcus aureus and Listeria monocytogenes are able to grow at refrigerator temperatures and cause food-borne disease

48
Q

Mesophilic (mesophiles)

A

Optimal growth between 20°C and 40°C; includes most human pathogens
Inhabit animals and plants as well as soil and water in temperate, subtropical, and tropical regions
Human pathogens have optimal growth temperatures between 30°C and 40°C

49
Q

Thermoduric

A

Mesophiles that can survive short exposure to high temperatures
Common contaminants of heated or pasteurized foods
E.g. heat resistant Giardia cysts and sporeformers such as Bacillus, Clostridium

50
Q

Thermophilic (thermophiles

A

Optimum growth temperatures between 45°C and 80°C

Live in soil and water associated with volcanic activity, compost piles, and in habitats directly exposed to the sun

51
Q

Hyperthermophilic (hyperthermophiles)

A

optimal growth from 80-121°C; none

52
Q

singlet oxygen (O)

A

an extremely reactive molecule that can damage and destroy a cell by the oxidation of membrane lipids

53
Q

superoxide ion (O2-):

A

highly reactive

54
Q

hydrogen peroxide (H2O2):

A

toxic to cells and used as a disinfectant

55
Q

hydroxyl radicals

A

Enzymes superoxide dismutase and catalase together neutralize some toxic oxygen compounds

56
Q

What are two enzymes that can help to

mitigate the effects of toxic products of oxygen?

A

Enzymes superoxide dismutase and catalase together neutralize some toxic oxygen compounds

57
Q

What are five categories of oxygen usage patterns in microbes?

A

1) Aerobes
2) Obligate (or strict) anaerobes
3) Facultative anaerobes
4) Microaerophiles
5) Aerotolerant anaerobes

58
Q

Which ones can use and/or detoxify oxygen?

A

Facultative anaerobes

Do not require oxygen for metabolism, but use and detoxify it when it is present.

59
Q

How could you identify each of these categories based on growth patterns in

agar shake tubes?

A

Lecture 4 Slide 30

60
Q

What are acidophiles and alkalinophiles?

A

Acidophiles: organisms with optimal growth in acidic environments (pH 8)

61
Q

What are osmophiles, halophiles, and obligate halophiles?

A

Osmophiles live in habitats with high solute concentration

62
Q

What are halophiles?

A

Halophiles prefer high concentration of salt

63
Q

What are obligate halophiles?

A

Obligate halophiles Halobacterium and Halococcus grow optimally at solutions of 25% NaCl but require at least 9% NaCl.
Facultative halophiles: remarkably resistant to salt, even though they do not normally reside in high salt environments

64
Q

What are the differences mutualism?

A

organisms live in an obligatory but mutually beneficial relationship

65
Q

What are the differences commensalism?

A

the partner called the commensal receives benefits, while its partner is neither harmed nor benefitted

66
Q

What are the differences parasitism?

A

: a relationship in which the host organism provides the parasitic microbe with nutrients and a habitat; parasite usually harms the host to some extent

67
Q

Symbiosis:

A

general term to denote a situation in which two organisms live together in a close partnership. Members of a symbiosis are symbionts

68
Q

How do synergism and antagonism differ from these?

A

Associations but Not Partnerships: Antagonism and Synergism

69
Q

Antagonism:

A

An association between free-living species that arises when members of a community compete

70
Q

Synergism:

A

An interrelationship between two organisms that benefits them but is not necessary for survival
Participants cooperate to produce a result that none of them could do alone
Gum disease, dental caries, and some bloodstream infections involve mixed infections of bacteria interacting synergistically
One great example of microbial synergism is in biofilms

71
Q

What are some steps in biofilm formation?

A

Formation of a biofilm
“Pioneer” colonizer attaches (e.g. via fimbriae) and grows on a surface
Other microbes then attach directly to pioneer bacteria or a polymeric sugar or protein substance secreted by the pioneer colonizers
Attached cells may release specific signaling chemicals such as quorum sensing signal molecules as the cell population grows

72
Q

What roles do attachment (e.g. by fimbriae),

glycocalyx, and quorum sensing play in biofilm formation?

A

Cells attach and adhere to surface (“colonize”), e.g. by use of fimbriae

73
Q

How are cells in biofilms different from planktonic cells?

A

quorum sensing signal molecules as the cell population grows

74
Q

Bacteria in biofilms behave and respond very differently than planktonic (free-living) bacteria?

A

Different genes are activated (e.g. due to quorum sensing)
Behave and respond very differently to their environments
Acting together, they can alter local environmental conditions

75
Q

Give an example of how biofilms can

create microenvironments that are different from the bulk environment regarding oxygen

A

O2 consumption at the surface may result in anaerobic conditions deeper within the biofilm

76
Q

What are major steps in the binary fission process of cell division?

A

Mother (parent) cell enlarges

Chromosomal DNA is replicated; copies are partitioned to each end of the mother cell

Mother cell starts to pull its cell envelope together to the center of the cell

Cell wall eventually forms a complete central septum

77
Q

How does binary fission lead to exponential increase in cell numbers?

A

When septum is complete, cells are considered divided. Some species will separate completely as shown here, while others remain attached, forming chains or doublets, for example.

78
Q

What is meant by the generation time or doubling time of a microbe?

A

The time required for a complete fission cycle, from parent cell to two daughter cells

79
Q

What is the typical range of doubling times of many pathogenic microbes?

A

Typical generation time for common pathogens and laboratory bacteria is 30 – 120 minutes

80
Q

 How can the equation Nt = (Ni)2n be used to calculate the doubling time, initial number of cells, or final number of cells in an exponentially growing microbial culture?

A

Cell population size can be represented by the number 2 with an exponent: 20=1, 21=2, 22=4, 23=8, 24=16, 25=32, etc.
The growth pattern is exponential.
Changes in cell numbers can conveniently be expressed in terms of logarithms

81
Q

What is the difference between batch culture and continuous culture? Which

A

In closed systems or batch cultures, numerous factors prevent cells from continuously dividing at their maximum rate

In open systems or continuous culture
nutrients are constantly supplied
Cells and medium are removed

82
Q

Which of these culturing methods are you (or will you) be using most in the lab section of the course?

A

Growth can be studied either in closed or open systems

In closed systems or batch cultures

83
Q

What are the four major stages in growth of a batch culture, and what is happening in each of these stages?

A
  • Lag phase is a “flat” period of growth due to
  • Exponential growth (logarithmic or log) phase
  • Stationary growth phase
  • Death phase
84
Q

Lag phase

A

is a “flat” period of growth due to
Newly inoculated cells require a period of adjustment, enlargement, and synthesis
Cells are not yet multiplying at their maximum rate
Population of cells is so sparse or dilute that growth is not easily observed

85
Q

Exponential growth (logarithmic or log) phase

A

Growth increases exponentially

Growth continues as long as adequate nutrients are available and the environment is favorable

86
Q

Stationary growth phase

A

Cell birth and cell death rates are equal
Cell division rate is slowing down
Caused by depleted nutrients and oxygen plus excretion of organic acids and biochemical pollutants into the growth medium

87
Q

Death phase

A

Cells begin to die at an exponential rate due to the buildup of wastes
Speed with which death occurs depends on the resistance of the species and how toxic the conditions are
Slower than the exponential growth phase

88
Q

During which of these stages might microbes be more vulnerable to heat or
antimicrobial agents?

A

Microbes in the exponential growth phase

89
Q

What are some examples of methods of enumerating microbes, and which are dependent on cultivation?

A

Viable plate counts

Turbidometry

90
Q

What are the steps used in performing a viable plate count for enumerating microbes, and what is a colony forming unit (CFU)?

A

Sampling a liquid culture, spreading on solid medium, incubating, and counting number of colonies.
Can be used over multiple time points to determine doubling time

Micro BIO 220 Part 1 (18 decks)

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