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Nutrition Flashcards

1
Q

Essential elements

A

CHNOPS Se

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2
Q

Nitrogen

A

Typical bacterial cell ~12% nitrogen (by dry weight)

Key element in proteins, nucleic acids, and many more cell constituents

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3
Q

Phosphorus (P)

A

Required by cell for synthesis of nucleic acids and phospholipids

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4
Q

Sulfur (S)

A

Plays structural role in S-containing amino acids (cysteine and methionine)

Present in several vitamins (e.g. thiamine, biotin, lipoic acid) and coenzyme A

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5
Q

Potassium (K)

A

Required by enzymes for activity

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6
Q

Magnesium (Mg)

A

Stabilizes ribosomes, membranes and nucleic acids

Also required for many enzymes

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7
Q

Calcium (Ca)

A

Helps stabilize cell walls in microbes

Plays key role in heat stability of endospores

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8
Q

Sodium (Na)

A

Required by some microbes (e.g., marine microbes)

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9
Q

Iron

A

Plays major role in cellular respiration; key component of cytochromes and FeS proteins involved in electron transport
Under anoxic conditions, generally ferrous (Fe2+) form; soluble
Under oxic conditions: generally ferric (Fe3+) form; exists as insoluble minerals
Cells produce siderophores(iron-binding agents) to obtain iron from insoluble mineral form

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10
Q

Most commonly required growth factors

Most function as coenyzmes

A

Vitamins

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11
Q

Culture Media

A

Nutrient solutions used to grow microbes in the laboratory

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12
Q

Defined media:

A

precise chemical composition is known

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13
Q

Complex media

A

composed of digests of chemically undefined substances

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14
Q

Contains compounds that selectively inhibit growth of some microbes but not others

A

Selective media

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15
Q

Contains an indicator, usually a dye, that detects particular chemical reactions occurring during growth

A

differential media

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16
Q

culture containing only a single kind of microbe

A

pure

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17
Q

unwanted organisms in a culture

A

Contaminants

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18
Q

time required for a population of microbial cells to double

A

generations

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19
Q

Variable among species depending on

A

Nutritional factors
Genetic factors
Temperature

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20
Q

Most species generation times

A

hours-days

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21
Q

Under optimal lab conditions

A

minutes

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22
Q

cell divide after unequal cell growth

A

Budding

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23
Q

Polar growth

A

New cell wall material forms from a single point (compared to binary fission where new cell wall material forms throughout the cell)

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24
Q

Large cytoplasmic structures are not partitioned and so

A

must be formed in the developing bud

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25
biofilm.. benefits?
Planktonic cells attach to a surface Build a polysaccharide matrix, cells embedded Resistant to chemicals, antibiotics, abrasion, grazers
26
Examples of biofilms
Toothbrush Implanted medical devices Cystic fibrosis
27
generation time
of the exponentially growing population is g = t/n
28
N = No2n can be expressed as
n = 3.3(log N– log N0)
29
Specific growth rate
(k) (aka instantaneous growth rate constant) rate at which the population is growing at any instant
30
Instantaneous rate of growth dN/dt=kN
A function of the number of cells at a given time Reexpress as N=N0ekt Take log10of both sides N=kt/2.303+log N0 k= 0.301/g(slope of semi-log plot)!!! since measures a doubling (x2) per generation time and log10of 2 is 0.301
31
Division rate(v) is calculated as
v= 1/g
32
Batch culture:
a closed-system microbial culture of fixed volume
33
Typical growth curve for population of cells grown in a closed system is characterized by four phases
Lag phase Exponential phase Stationary phase Death phase
34
Lag phase
Interval of time between when a culture is inoculated and when growth begins
35
Exponential phase
Cells in this phase are typically in the healthiest state
36
Stationary phase and Death
Net growth rate of population is zero One divides, one dies = cryptic growth Either an essential nutrient is used up or waste product of the organism accumulates in the medium Death phase is exponential
37
Continuous culture
an open-systemmicrobial culture of fixed volume
38
most common type of continuous culture device
Chemostat
39
Both growth rate and population density of culture can be controlled independently and simultaneously by:
Dilution rate: rate at which fresh medium is pumped in and spent medium pumped out Concentrationof a limiting nutrient
40
Microbial cells can be enumerated by
microscopic observations; simple but results can be unreliable
41
Limitations of microscopic counts
Cannot distinguish between live and dead cells without special stains - Small cells difficult to see and can be overlooked - Precision is difficult to achieve - A phase-contrast microscope is required if a stain is not used
42
Measurement of living, reproducing population is
Viable cell counts (plate counts)
43
Two main ways to perform plate counts
Spread-plate method Pour-plate method
44
To obtain the appropriate colony number, the sample to be counted should always be
diluted
45
Colony counts should be between ??? (colony-forming units) to be accurate
30 –300 cfu
46
??? is Typically more accurate than spread plates but counts are usually lower because heat-sensitive cells will not grow after interacting with heated agar
pour-plate
47
Plate counts can be highly ??
unreliable when used to assess total cell numbers of natural samples (e.g., soil and water)
48
The Great Plate Anomaly:
Direct microscopic counts of natural samples typically reveal far more organisms than are recoverable on plates of any given culture medium
49
The Great Plate Anomaly results in
viable but non-cultivable cells (VBNC)
50
Why viable but non-cultivable cells (VBNC) ?
Microscopic methods count dead cells whereas viable methods do not Different organisms in even a very small sample may have vastly different requirements for resources and conditions in laboratory culture
51
? measurements are an indirect but very rapid and useful method of measuring microbial growth
Turbidity; often use spectrophotometer and optical density.
52
is a major environmental factor controlling microbial growth
Temperature
53
As temperatures rise, rate of enzymatic reactions
increases and growth rate becomes faster | BUT at a certain temperature, proteins denature and growth slows
54
the minimum, optimum, and maximum temperatures at which an organism grows
cardinal temperatures
55
Psychrophile
low temperature
56
growth is not possible at
min and max temperatures only at optimal
57
Mesophile
midrange; warm blooded , e coli
58
thermophile
high temp
59
hyperthermophile
very high temp
60
Extremophiles
very hot or very cold
61
psychrophiles
cod optima; inhabit permanently cold environments
62
Psychotolerant
Organisms that can grow at 0ºC but have optima of 20ºC to 40ºC; more widely distributed in nature than psychrophiles
63
What are the molecular adaptation that allow psychrophily
More α-helices, fewer β-sheets -α-helices provide more flexibility for catalyzing at low temperatures More polar and fewer hydrophobic amino acids Fewer weak bonds Decreased interactions between protein domains Transport processes function optimally at low temperatures due to modifications of cytoplasmic membranes High unsaturated fatty acid content Cytoplasmic membranes remain semi-fluid at low temperatures
64
Which life form only exists above Above ~65°C
Prokaryotes
65
Hyperthermophiles in Hot Springs
Chemoorganotrophic (energy from organic chemicals) and chemolithotrophic (energy from inorganic compounds) species present High prokaryotic diversity (both Archaea and Bacteria represented) Organisms with the highest temperature optima areArchaea
66
What are the allowances for Molecular Adaptations to Thermophily
Enzyme and proteins function optimally at high temperatures; features that provide thermal stability: Critical amino acid substitutions in a few locations provide more heat-tolerant folds An increased number of ionic bonds between basic and acidic amino acids resist unfolding in the aqueous cytoplasm Production of solutes (e.g., di-inositol phosphate, diglyercol phosphate) help stabilize proteins Modifications in cytoplasmic membranes to ensure heat stability Bacteria have lipids rich in saturated fatty acids Archaea have lipid monolayer rather than bilayer Monolayer prevents the cytoplasmic membrane from melting because of covalent links between membrane
67
What temperature resistant bacteria produce enzymes widely used in industrial microbiology? Example?
Hyperthermophiles | TAQ Polymerae
68
Other than temperature, what are Other Environmental Factors Affecting Growth
Microbial Growth at Low or High pH Osmotic Effects on Microbial Growth Oxygen and Microbial Growth Toxic Forms of Oxygen
69
Most organisms grow best between pH 6 and 8
neutrophiles
70
Acidophiles
organisms that grow best at low pH (< 6) Some obligate acidophiles; membranes destroyed at neutral pH Stability of cytoplasmic membrane critical
71
However, The internal pH of a cell must stay relatively
close to neutral even though the external pH is highly acidic or basic.
72
Osmotic Effects on Microbial Growth | Typically, the cytoplasm has
a higher solute concentration than the surrounding environment, thus the tendency is for water to move into the cell (positive water balance)
73
water will flow out unless the cell has a mechanism to prevent this
water will flow out unless the cell has a mechanism to prevent this
74
Halotoleration
organisms that can tolerate some reduction in water activity of environment but generally grow best in the absence of the added solute
75
Mechanisms for combating low water activity (unbound water) in surrounding environment involve increasing the internal solute concentration by
water activity scale extends from 0 (bone dry) to 1.0 (pure water) Pumping inorganic ions from environment into cell Synthesis or concentration of organic solutes compatible solutes: compounds used by cell to counteract low water activity in surrounding environment Often sugars, alcohols, or derived amino acidsSome use KCl
76
Several toxic forms of oxygen can be formed in the cell – occur during reduction of O2 to water
Single oxygen (O) Superoxide anion (O2- )Hydrogen peroxide (H2O2) Hydroxyl radical (OH.)
77
Catalase and peroxidase attack H2O
forming O2 and H2

Microbiology (12 decks)

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