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Microbiology > Ch 6: Microbial Nutrition and Growth > Flashcards

Ch 6: Microbial Nutrition and Growth Flashcards

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Biology 101 flashcards
1
Q

What is microbial growth?

A

orderly and permanent Increase of the mass of an individual or a population of microbes

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2
Q

What is the result of microbial growth/reproduction?

A

Result of microbial growth is discrete colony

An collection of cells arising from single parent cell

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3
Q

What is microbial reproduction?

A

Reproduction is an increase in the numbers of individuals and can be independent of growth, although the result of reproduction is usually growth

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4
Q

Describe microbial growth requirements

What are most common elements needed in nutrition?

A

Organisms use a variety of nutrients for their energy needs and to build cellular structures

Most common nutrients contain necessary elements such as carbon, oxygen, nitrogen, and hydrogen

Microbes obtain nutrients from variety of sources

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5
Q

Describe two groups of organisms based on source of energy and source of carbon (chemical and energy requirements)

A

Nutrients: Sources of carbon, energy, and electrons

Two groups of organisms based on source of energy
Chemotrophs - from food
Phototrophs - from light

Two groups of organisms based on source of carbon
Autotrophs - breathing CO2
Heterotrophs - CO2 from food

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6
Q

Describe the effect of temperature on proteins and the effect of temperature on membranes of cells and organelles

A

Effect of temperature on proteins
Very high temperatures can cause denaturing

Effect of temperature on membranes of cells and organelles
If too low, membranes become rigid and fragile
If too high, membranes become too fluid

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7
Q

What is the temperature range for psychrophiles?

A

“Cold-lovers”

-5C to 20C

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8
Q

What is the temperature range for mesophiles?

A

“Middle-loving”

15C to 45C

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9
Q

What is the temperature range for thermophiles?

A

“Heat-lovers”

45C to 80C

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10
Q

What is the temperature range for hyperthermophiles?

A

68C to 105C

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11
Q

What is osmotic pressure?

A

Pressure exerted on a semi-permeable membrane by a solution containing solutes that cannot freely cross membrane

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12
Q

How will water move if it is an isotonic solution?

A

Isotonic solution: no net movement of water

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13
Q

How will water move if it is an hypotonic solution?

A

water will move into cell (cell swells up and can lyse

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14
Q

How will water move if it is an hypertonic solution?

A

water moves out of cell (cell shrinks, plasmolysis)

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15
Q

How does osmotic pressure affect organisms related to their environment? Give an example.

A

Restricts organisms to certain environments.

Obligate and Facultative Halophiles: grow in high salt conditions.

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16
Q

What organism lives under extreme water pressure? Why?

A

Water exerts pressure in proportion to its depth

Barophiles live under extreme pressure
Their membranes and enzymes depend on pressure to maintain their shape

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17
Q

Describe oxygen requirements for bacterial growth

A

Oxygen is essential for obligate aerobes

Oxygen is deadly for obligate anaerobes

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18
Q

Why is oxygen deadly for obligate anaerobes?

A

Toxic forms of oxygen are highly reactive and excellent oxidizing agents
Resulting oxidation causes irreparable damage to cells

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19
Q

Describe oxygen affects on growth

How do bacteria deal with toxic byproducts of oxygen?

A

organisms can produce more energy when growing in oxygen, but toxic byproducts of oxygen can be fatal to cells

Toxic byproducts from use of O2
Superoxide Radical – extremely toxic to living cells. This harmful molecule is neutralized by the enzyme superoxide dismutase (SOD) which is produced by all organisms growing in the presence of oxygen. SOD converts superoxide radical to hydrogen peroxide (H2O2) & O2

hydrogen peroxide is still toxic; this will be dealt with shortly

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20
Q

How is hydrogen peroxide neutralized?

A

Hydrogen peroxide can be neutralized using two enzymes

Catalase 2 H2O2 –> 2 H20 + O2
presence of this enzyme in an organism can be detected by applying hydrogen peroxide to a culture (on solid media) and observing presence of bubbles

Peroxidase H2O2 + 2 H+ –> 2 H20
because this reaction doesn’t produce gaseous oxygen, no bubbling can be seen when applying hydrogen peroxide (doesn’t really ask about)

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21
Q

What are the classifications of organisms by O2 requirements?

A

Obligate Aerobes: require oxygen for growth

Facultative Anaerobes: can grow with or without oxygen, but prefer without

Obligate Anaerobes: CANNOT tolerate molecular oxygen

Microaerophiles: require oxygen, but can only grow at low oxygen tension (doesn’t ask about)

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22
Q

Describe nitrogen requirements of bacterial growth

A

Anabolism often ceases because of insufficient nitrogen

Nitrogen is acquired from organic and inorganic nutrients

All cells recycle nitrogen from amino acids and nucleotides

Nitrogen fixation by certain bacteria is essential to life on Earth (really only cares about this statement)
-N2 permeates soil, bacteria/fungus in root nodules convert N2 into NH4, NO2, NO3, plant is able to use this

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23
Q

What are four other chemical requirements for bacterial growth?

A

Phosphorus

Sulfur

Trace elements
Required only in small amounts – usually metals like Zinc, Manganese, Chromium, etc.

Growth factors
Necessary organic chemicals that cannot be synthesized by certain organisms

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24
Q

What does culturing involve? What is a culture?

A 
Inoculum introduced into medium
-Environmental specimens
-Clinical specimens
-Stored specimens
Culture 
-Act of cultivating microorganisms or the microorganisms that are cultivated
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25
Q

What is a pure culture and how do you obtain a pure culture?

A

Cultures composed of cells arising from a single progenitor called a CFU (colony forming unit)

Aseptic technique prevents contamination of sterile substances or objects

Two common isolation techniques

  • Streak plates
  • Pour plates
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26
Q

What is a spread plate? (Doesn’t really care about)

A

Spread plate – a diluted liquid inoculum is spread over surface of a plate

27
Q

What is a pour plate? (Doesn’t really care about)

A

Pour plate – a diluted liquid inoculum is mixed with melted nutrient agar and colonies are allowed to grow

28
Q

What is a broth and what is it best used for?

A

Broths - propagation (rapid growth) of cultures

29
Q

What is a slant and what is it best used for?

A

Slants – maintenance of cultures (used as back up)

30
Q

Describe solid media

A

a synthetic or complex medium can be solidified using agar, a product harvested from red algae (1.5% agar). Agar gives a nice surface for growing bacteria (often used to maintain cultures)

31
Q

Describe semi-solid media

A

usually 0.5% agar, used for motility studies (SIM medium), looks solid, but tears really easily

32
Q

Describe liquid media

A

not agar, but broth; used for propagation of cultures

33
Q

Describe culture media

A

nutrient material prepared for the growth of microorganisms in the laboratory (must initially be sterile)

34
Q

Describe synthetic medium

A

AKA Defined Medium
made of KNOWN amounts of chemicals (E. coli minimal salt)
Defined proportions of ingredients

35
Q

Describe complex medium

A

Complex medium: some ingredients are of unknown (undefined ) composition or amount (extracts of plants, yeast or meat)

  • Nutrient broth / TSA
  • Tryptic soy broth (TSB)
36
Q

What does a general medium do?

A

provides basic needs of organism

Doesn’t say much, skip this slide

37
Q

What is a selective medium? Give two examples

A

encourages the growth of certain organisms while discouraging the growth of others:

  • selective for Gram- (MacConkey), EMB
  • selective for Gram+ (Columbia)
38
Q

What is a differential medium? Give two examples

A

distinguishes between different groups of bacteria - the media contains constituents which cause an observable change (color or pH change)

  • MacConkey contains lactose and neutral red, lactose fermenters appear pink
  • Blood agar - shows hemolysis
39
Q

Name the three types of hymolysis and what they look like

A

No hemolysis (gamma-hymolysis shows as red or no change

Alpha-hemolysis has a green sheen

Beta-hemolysis red blood color is completely gone

40
Q

What does it indicate about the bacteria if it shows up on a MacConkey plate? What if it does not show up?

A

If it shows up it is Gram -

If it does not show up it is either Gram + or AF (acid fast)

41
Q

What does a bacteria indicate if it turns pink on a MacConkey plate? What if it shows up, but is not pink?

A

Pink: Gram -, lactose fermenter

No pink/change: Gram -, not a lactose fermenter

42
Q

What does a PR test tell you when the result is red? Yellow? What if there is a bubble? Without a bubble?

A

Red: No acid fermentation

Yellow: Acid fermentation (could be maltose, fructose, glucose, or mannitol)

No bubble: No gas produced

Bubble: Gas produced

43
Q

What are special culture techniques?

A

Techniques developed for culturing microorganisms

  • Animal and cell culture
  • Low-oxygen culture (vacuum out air)
  • Enrichment culture (bacteria is fastidious, a lot of nutrients needed for growth)
44
Q

What special media/conditions would you need to cultivate anaerobes?

A
  1. Reducing media (chemical to remove oxygen) (modern0
  2. Non-oxygen atmosphere (candle jar or anaerobic jar)
  3. Enrichment medium: provide conditions which will only allow bacteria with a specific desired trait to survive and grow (particular carbon source, growth conditions, etc.).
    [Sabouraud’s dextrose agar (fungi)]
45
Q

What are three ways to preserve cultures?

A
  1. Refrigeration- stores for short periods of time
  2. Deep-freezing- stores for years
  3. Lyophilization- stores for decades (freeze drying)
46
Q

Describe bacterial division

A

Binary fission produces two identical cells, each with one full chromosome

47
Q

Describe generation time

A

Bacterial division: binary fission produces two identical cells, each with one full chromosome

Generation time: Dependent on chemical and physical conditions, it’s the time required for cells to divide, thus doubling the population – can be as short as 20 minutes or longer than a day

48
Q

What is the name of the scale which shows a curved line on a graph to represent exponential growth?

A

Arithmetic coordinates (e.g. 1000, 2000, 3000, etc)

49
Q

What is the name of the scale which shows a straight line on a graph to represent exponential growth?

A

Logarithmic coordinates (e.g. 10^1, 10^2, 10^3, etc)

50
Q

When looking at a growth curve, what is the first line representing low, but constant number of live cells?

A

Lag phase: metabolizing and growing, but not replicating

51
Q

When looking at a growth curve, what is the line that increases constantly showing exponential growth of live cells?

A

Log (exponential) phase

52
Q

When looking at a growth curve, what is the straight line representing high, constant number of live cells?

A

Stationary phase

birth rate = death rate

53
Q

When looking at a growth curve, what is the line showing exponential decrease of live cells?

A

Death (decline) phase

54
Q

What is it called if bacteria grow one at time?

A

Growing arithmetically

55
Q

What is it called when bacteria grow by doubling?

A

Growing exponentially or logarithmically

56
Q

What are four ways to measure bacterial growth?

A
  1. Plate counts (serial dilutions or “colony counting”) : increase in number of bacteria through time - each colony represents one bacterium
  2. Filtration
  3. Most probable number (MPN)
  4. Direct microscopic count
57
Q

Describe plate counts (serial dilution or “colony counting)

A

increase in number of bacteria through time - each colony represents one bacterium (diluting by 10x each time)

58
Q

Describe filtration (not on test)

A

known volume of bacterial culture collected on a filter disk then the disk is placed in media and allowed to grow - each colony represents one bacterium in original sample

59
Q

Describe most probably number (MPN)

A

statistical method for estimating numbers

60
Q

Describe direct microscopic count

A

Petroff-Hausser (grid) counter: counting how many in a grid then multiplying by how many grids

61
Q

Explain MPN

A

Most Probable Number Method uses statistics to provide an estimate of number of bacteria in a given sample.
In the book’s example you inoculate three sets of five tubes

Our original sample has 100ml total volume.
Question, how many bacteria does this contain?

Series 1 tubes each get 10 ml of the original sample.

Series 2 tubes each get 1 ml of original sample.

Series 3 tubes each get 0.1 ml of original sample

Look at positive (yellow) results in each set and look up that number series on provided chart (e.g 4 positive tubes in set one, 2 positive tubes in set two, 1 positive tube in set three = 4-2-1)

62
Q

How would you word the MPN test results?

A

“As few as ___, as many as ___, most probable number is ___”

or

“95% of the time, a sample giving this pattern will have at least __ bacteria in original sample possibly as many as __. The average number of bacteria in a sample with this pattern is __.

63
Q

Describe measuring microbial reproduction

A

Measuring Microbial Reproduction

  • Genetic methods
  • -Isolate DNA sequences of unculturable prokaryotes (they can’t grow well)
  • –Used to estimate the number of these microbes
64
Q

Describe how a spectrometer works (bonus)

A

Light source travels through a tube to a light-sensitive detector. The spectrophotometer (spectrometer) reads the percent of light transmitted.
An uninoculated tube will read close to 100 percent light transmitted. In an inoculated broth, the culture will scatters the light, which will not reach the reflector, causing the percentage of light transmitted to be lower.

Microbiology (7 decks)

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