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Micro BIO 220 Part 1 > Lecture 4 > Flashcards

Lecture 4 Flashcards

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
What is a plaque assay, and what type of microbe is this used to grow?
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.
26
What “ingredients” are necessary for performing a plaque assay?
soft agar overlay
27
What is a plaque forming unit (PFU)?
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.
28
Isotonic conditions
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
29
Hypotonic conditions
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
30
Hypertonic conditions
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
31
Isotonic solution
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.
32
Hypotonic solution
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
33
Hypertonic solution
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.
34
Passive transport:
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
35
Active transport
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
36
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 Only in Eukaryotes
37
For prokaryotes, macromolecules are usually
broken down by secreted, extracellular enzymes prior to transport.
38
Endocytosis: “eating or drinking” by eukaryotic cells Called phagocytosis
if a solid is transported
39
Endocytosis: “eating or drinking” by eukaryotic cells Called pinocytosis
if a liquid is transported
40
what are Environmental Factors That Influence Microbes?
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
large groups of microbes can indeed have large affects on their
local environment
42
Cardinal temperatures?
Three temperatures that summarize how temperature limits growth of a given microbe
43
Minimum temperature ?
the lowest temperature that permits a microbe’s continued growth and metabolism; below this temperature, its activities are limited (protein function, membrane fluidity)
44
Optimum temperature ?
an intermediate between the minimum and the maximum which promotes the fastest rate of growth and metabolism
45
Maximum temperature?
the highest temperature at which growth and metabolism can proceed, often due to denaturation (unfolding) of key proteins and/or membrane loses integrity
46
Psychrophilic (psychrophiles)
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
Psychrotrophic (psychrotrophs)
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
Mesophilic (mesophiles)
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
Thermoduric
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
Thermophilic (thermophiles
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
Hyperthermophilic (hyperthermophiles)
optimal growth from 80-121°C; none
52
singlet oxygen (O)
an extremely reactive molecule that can damage and destroy a cell by the oxidation of membrane lipids
53
superoxide ion (O2-):
highly reactive
54
hydrogen peroxide (H2O2):
toxic to cells and used as a disinfectant
55
hydroxyl radicals
Enzymes superoxide dismutase and catalase together neutralize some toxic oxygen compounds
56
What are two enzymes that can help to | mitigate the effects of toxic products of oxygen?
Enzymes superoxide dismutase and catalase together neutralize some toxic oxygen compounds
57
What are five categories of oxygen usage patterns in microbes?
1) Aerobes 2) Obligate (or strict) anaerobes 3) Facultative anaerobes 4) Microaerophiles 5) Aerotolerant anaerobes
58
Which ones can use and/or detoxify oxygen?
Facultative anaerobes | Do not require oxygen for metabolism, but use and detoxify it when it is present.
59
How could you identify each of these categories based on growth patterns in agar shake tubes?
Lecture 4 Slide 30
60
What are acidophiles and alkalinophiles?
Acidophiles: organisms with optimal growth in acidic environments (pH 8)
61
What are osmophiles, halophiles, and obligate halophiles?
Osmophiles live in habitats with high solute concentration
62
What are halophiles?
Halophiles prefer high concentration of salt
63
What are obligate halophiles?
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
What are the differences mutualism?
organisms live in an obligatory but mutually beneficial relationship
65
What are the differences commensalism?
the partner called the commensal receives benefits, while its partner is neither harmed nor benefitted
66
What are the differences parasitism?
: 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
Symbiosis:
general term to denote a situation in which two organisms live together in a close partnership. Members of a symbiosis are symbionts
68
How do synergism and antagonism differ from these?
Associations but Not Partnerships: Antagonism and Synergism
69
Antagonism:
An association between free-living species that arises when members of a community compete
70
Synergism:
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
What are some steps in biofilm formation?
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
What roles do attachment (e.g. by fimbriae), | glycocalyx, and quorum sensing play in biofilm formation?
Cells attach and adhere to surface (“colonize”), e.g. by use of fimbriae
73
How are cells in biofilms different from planktonic cells?
quorum sensing signal molecules as the cell population grows
74
Bacteria in biofilms behave and respond very differently than planktonic (free-living) bacteria?
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
Give an example of how biofilms can | create microenvironments that are different from the bulk environment regarding oxygen
O2 consumption at the surface may result in anaerobic conditions deeper within the biofilm
76
What are major steps in the binary fission process of cell division?
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
How does binary fission lead to exponential increase in cell numbers?
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
What is meant by the generation time or doubling time of a microbe?
The time required for a complete fission cycle, from parent cell to two daughter cells
79
What is the typical range of doubling times of many pathogenic microbes?
Typical generation time for common pathogens and laboratory bacteria is 30 – 120 minutes
80
 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?
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
What is the difference between batch culture and continuous culture? Which
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
Which of these culturing methods are you (or will you) be using most in the lab section of the course?
Growth can be studied either in closed or open systems | In closed systems or batch cultures
83
What are the four major stages in growth of a batch culture, and what is happening in each of these stages?
- Lag phase is a “flat” period of growth due to - Exponential growth (logarithmic or log) phase - Stationary growth phase - Death phase
84
Lag phase
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
Exponential growth (logarithmic or log) phase
Growth increases exponentially | Growth continues as long as adequate nutrients are available and the environment is favorable
86
Stationary growth phase
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
Death phase
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
During which of these stages might microbes be more vulnerable to heat or antimicrobial agents?
Microbes in the exponential growth phase
89
What are some examples of methods of enumerating microbes, and which are dependent on cultivation?
Viable plate counts | Turbidometry
90
What are the steps used in performing a viable plate count for enumerating microbes, and what is a colony forming unit (CFU)?
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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