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Microbiology > Nutrition > Flashcards

Nutrition Flashcards

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Biology 101 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
Q

biofilm.. benefits?

A

Planktonic cells attach to a surface
Build a polysaccharide matrix, cells embedded

Resistant to chemicals, antibiotics, abrasion, grazers

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26
Q

Examples of biofilms

A

Toothbrush
Implanted medical devices
Cystic fibrosis

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27
Q

generation time

A

of the exponentially growing population is g = t/n

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28
Q

N = No2n can be expressed as

A

n = 3.3(log N– log N0)

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29
Q

Specific growth rate

A

(k) (aka instantaneous growth rate constant) rate at which the population is growing at any instant

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30
Q

Instantaneous rate of growth dN/dt=kN

A

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

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31
Q

Division rate(v) is calculated as

A

v= 1/g

32
Q

Batch culture:

A

a closed-system microbial culture of fixed volume

33
Q

Typical growth curve for population of cells grown in a closed system is characterized by four phases

A

Lag phase
Exponential phase
Stationary phase
Death phase

34
Q

Lag phase

A

Interval of time between when a culture is inoculated and when growth begins

35
Q

Exponential phase

A

Cells in this phase are typically in the healthiest state

36
Q

Stationary phase and Death

A

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
Q

Continuous culture

A

an open-systemmicrobial culture of fixed volume

38
Q

most common type of continuous culture device

A

Chemostat

39
Q

Both growth rate and population density of culture can be controlled independently and simultaneously by:

A

Dilution rate: rate at which fresh medium is pumped in and spent medium pumped out

Concentrationof a limiting nutrient

40
Q

Microbial cells can be enumerated by

A

microscopic observations; simple but results can be unreliable

41
Q

Limitations of microscopic counts

A

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
Q

Measurement of living, reproducing population is

A

Viable cell counts (plate counts)

43
Q

Two main ways to perform plate counts

A

Spread-plate method

Pour-plate method

44
Q

To obtain the appropriate colony number, the sample to be counted should always be

A

diluted

45
Q

Colony counts should be between ??? (colony-forming units) to be accurate

A

30 –300 cfu

46
Q

??? is Typically more accurate than spread plates but counts are usually lower because heat-sensitive cells will not grow after interacting with heated agar

A

pour-plate

47
Q

Plate counts can be highly ??

A

unreliable when used to assess total cell numbers of natural samples (e.g., soil and water)

48
Q

The Great Plate Anomaly:

A

Direct microscopic counts of natural samples typically reveal far more organisms than are recoverable on plates of any given culture medium

49
Q

The Great Plate Anomaly results in

A

viable but non-cultivable cells (VBNC)

50
Q

Why viable but non-cultivable cells (VBNC) ?

A

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
Q

? measurements are an indirect but very rapid and useful method of measuring microbial growth

A

Turbidity; often use spectrophotometer and optical density.

52
Q

is a major environmental factor controlling microbial growth

A

Temperature

53
Q

As temperatures rise, rate of enzymatic reactions

A

increases and growth rate becomes faster

BUT at a certain temperature, proteins denature and growth slows

54
Q

the minimum, optimum, and maximum temperatures at which an organism grows

A

cardinal temperatures

55
Q

Psychrophile

A

low temperature

56
Q

growth is not possible at

A

min and max temperatures only at optimal

57
Q

Mesophile

A

midrange; warm blooded , e coli

58
Q

thermophile

A

high temp

59
Q

hyperthermophile

A

very high temp

60
Q

Extremophiles

A

very hot or very cold

61
Q

psychrophiles

A

cod optima; inhabit permanently cold environments

62
Q

Psychotolerant

A

Organisms that can grow at 0ºC but have optima of 20ºC to 40ºC; more widely distributed in nature than psychrophiles

63
Q

What are the molecular adaptation that allow psychrophily

A

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
Q

Which life form only exists above Above ~65°C

A

Prokaryotes

65
Q

Hyperthermophiles in Hot Springs

A

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
Q

What are the allowances for Molecular Adaptations to Thermophily

A

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
Q

What temperature resistant bacteria produce enzymes widely used in industrial microbiology? Example?

A

Hyperthermophiles

TAQ Polymerae

68
Q

Other than temperature, what are Other Environmental Factors Affecting Growth

A

Microbial Growth at Low or High pH

Osmotic Effects on Microbial Growth

Oxygen and Microbial Growth

Toxic Forms of Oxygen

69
Q

Most organisms grow best between pH 6 and 8

A

neutrophiles

70
Q

Acidophiles

A

organisms that grow best at low pH (< 6)
Some obligate acidophiles; membranes destroyed at neutral pH

Stability of cytoplasmic membrane critical

71
Q

However, The internal pH of a cell must stay relatively

A

close to neutral even though the external pH is highly acidic or basic.

72
Q

Osmotic Effects on Microbial Growth

Typically, the cytoplasm has

A

a higher solute concentration than the surrounding environment, thus the tendency is for water to move into the cell (positive water balance)

73
Q

water will flow out unless the cell has a mechanism to prevent this

A

water will flow out unless the cell has a mechanism to prevent this

74
Q

Halotoleration

A

organisms that can tolerate some reduction in water activity of environment but generally grow best in the absence of the added solute

75
Q

Mechanisms for combating low water activity (unbound water) in surrounding environment involve increasing the internal solute concentration by

A

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
Q

Several toxic forms of oxygen can be formed in the cell – occur during reduction of O2 to water

A

Single oxygen (O)
Superoxide anion (O2-
)Hydrogen peroxide (H2O2)
Hydroxyl radical (OH.)

77
Q

Catalase and peroxidase attack H2O

A

forming O2 and H2

Microbiology (12 decks)

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