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Applications for biology > 1.2: Techniques for microbiology > Flashcards

1.2: Techniques for microbiology Flashcards

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1
Q

What is phototrophs?

A

Absorption of light energy

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2
Q

What are the two sources of energy living organisms can get a continuous supply from?

A
  • phototrophs
  • chemotrophs
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3
Q

What is chemotrophs?

A

Chemical potential energy in food

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4
Q

What are the 2 sources of carbon organisms get their supply from?

A
  • Autotrophs
  • Heterotrophs
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5
Q

What are autotrophs?

A

Inorganic carbon (CO₂)

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6
Q

What are heterotrophs?

A

organic compounds (e.g. sugars)

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7
Q

Why do in vitro microorganisms need nutrients for?

A
  • To generate ATP/energy source
  • To synthesise cell materials
  • must be present in the culture medium
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8
Q

What must the culture medium contain?

A

all necessary nutrients in sufficient quantities

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9
Q

What is a synthetic culture media?
+ uses

A
  • Made from laboratory chemicals in carefully measured quantities
  • for growing microorganisms when you know their exact requirements
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10
Q

What is complex culture media?
+ uses

A
  • contains some ingredients of unknown chemical composition
  • for growing a wide range of microorganisms or when the requirements are not known
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11
Q

What is selective culture media?
+ uses

A
  • very specialised, suitable for growing a specific organism
  • diagnostics (e.g. detecting salmonella in faeces)
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12
Q

Why is carbon needed for microorganism growth?

A

To build organic molecules (e.g. proteins, carbohydrates)

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13
Q

Why is nitrogen needed for microorganism growth?

A

To build protein and nucleic acid (DNA, RNA)

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14
Q

Why is sulphur needed for microorganism growth?
+ source

A

To build amino acids
+ many need to be provided as sulphates

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15
Q

What minerals are needed for microorganism growth?

A
  • macronutrients (potassium, magnesium and phosphate)
  • micronutrients (manganese, cobalt, copper, zinc, molybdenum)
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16
Q

What does potassium do for microorganisms?

A

Enzyme cofactors

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17
Q

What does magnesium do for microorganisms?

A

help make Chlorophyll

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18
Q

What does phosphate do for microorganisms?

A

Make ATP/DNA

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19
Q

Why are minerals needed for microorganism growth?

A

For enzymes to function, often act as cofactors

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20
Q

Why are growth factors needed/controlled for microorganism growth?

A
  • Cannot be synthesised from simpler substances
  • include Amino acids, purines and pyrimidines (nucleotides), vitamins
  • Needed to make proteins, DNA and cofactors for enzymes
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21
Q

What are thermophiles?

A

microorganisms that have optimum temperatures at which their enzymes will function above 40 degrees

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22
Q

What are mesophiles?

A

microorganisms that have optimum temperatures at which their enzymes will function between 20 - 40 degrees

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23
Q

What are psychrophiles?

A

microorganisms that have optimum temperatures at which their enzymes will function below 20 degrees

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24
Q

What PH do most bacteria grow best at?

A

PH 7, preferring to grow on the range 6-8

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25
Q

What PH do few bacteria grow at?

A

Below a PH of 4

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26
Q

What is the extreme that bacteria can grow at? specifically Thiobacillus thiooxidans

A

0

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27
Q

What do photoautotrophs and chemoautotrophs use as their carbon source?

A

Carbon dioxide

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28
Q

What do heterotrophs use as their carbon source?

A

Complex organic molecules, such as cellulose

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29
Q

What source does nitrogen use?

A
  • some microorganisms can fix atmospheric nitrogen
  • many take up nitrogen as nitrates
  • some microorganisms need the ammonium, ion rather than nitrate
30
Q

How are macronutrients sourced?

A

As salts in the culture media

31
Q

How are macronutrients sourced?

A

often present in adequate amounts as contaminants (e.g. in tap water used)

32
Q

Where are growth factors sourced?

A

needed in small quantities and added to the culture medium

33
Q

What is the source of oxygen requirements?

A
  • water in the culture medium containing oxygen
  • atmospheric oxygen
34
Q

How is temperature sourced for microorganisms?

A

incubator or warming/cooling jacket

35
Q

How is PH Sourced for microorganisms?

A
  • often produce waste products which alter the pH of the medium, buffers are added
36
Q

What are buffers?

A

substances that maintain the pH

37
Q

How do you aseptically pour an agar plate?

A
  • hold flask top in one hand and discard plug into disinfectant
  • flame mouth of flask
  • mix and pour immediately into sterile Petri dishes
  • allow plates to set (15 min approx.)
38
Q

How do you create a bacterial lawn?

A
  • sample is pipetted onto surface of agar plate (0.1ml or less)
  • sample is spread evenly over surface using glass spreader
  • incubate
  • surface colonies
39
Q

How do you do the pour plate method?

A
  • sample is pipetted into the sterile plate
  • sterile medium is added and mixed well with inoculum
  • incubate
  • should see subsurface and surface colonies
40
Q

What are the differences between - pour plates - VS Spread plate

A
  • obligate / facultative anaerobes / aerobes
  • large volumes of inoculum
  • bacteria grow on surface and subsurface colonies
  • large surface area for colony growth
  • don’t always get an even distribution of colonies
  • organisms may die if agar is too hot
  • may be difficult to pick out colony growing in agar
41
Q

What are the differences between pour plates VS - Spread plate -

A
  • aerobic organisms
  • only use small volumes of inoculum
  • bacteria only grow on surface
  • smaller surface area for colony growth
  • more even distribution of colonies
  • agar is already set, bacteria won’t die
  • picking a colony from the plate is less likely to disturb other colonies
42
Q

What does pick out mean, in terms of colonies?

A

select colonies and grow in different media

43
Q

What are obligate anaerobes?

A

microorganisms that will die in O₂

44
Q

what are facultative anaerobes?

A

can survive with O₂ and can survive without

45
Q

What is obligate aerobes?

A

Need oxygen to survive

46
Q

How do you produce a streak plate?

A
  • hold inoculating loop in flame
  • remove lid from culture
  • pass neck of bottle through the flame
  • dip the cool loop into the broth culture
  • flame neck again
  • raise lid of Petri dish with other hand, only enough to allow loop inside. streak surface in three parallel lines
  • resterilise loop and break as shown. sterilise loop at each corner
  • seal dish with adhesive tape and incubate (don’t tape fully shut - need O₂)
47
Q

What is the purpose of a streak plate?

A
  • isolate pure colonies with incubation due to diluted quantity of bacterial culture
  • separates mixed cultures into pure ones as each colony grows from a single cell
48
Q

How do you perform the inoculating stab technique?

A
  • use a sterile straight wire to inoculate a stab medium
  • stab through the centre of the medium taking care to withdraw the wire along the line of the inoculum without making further stab lines
49
Q

What does the stab method used to indicate?

A
  • motility of bacteria
  • oxygen requirements of bacteria for growth
50
Q

Bacterial growth curves - LAG phase

A

Growth is slow as there are only a few bacteria to divide. The microbes are adjusting to the food supply and making the enzymes needed to use the supplied nutrients

51
Q

Bacterial growth curves - LOG phase

A

Maximum rate of cell division fission. Good supply of nutrients and little build-up of toxic waste

52
Q

Bacterial growth curves - Stationary Phase

A

Cell division equals cell death due to competition for food and toxic waste build up. Carrying capacity has been reached

53
Q

What is carrying capacity (bacterial growth curves)

A

The maximum population size the environment can sustain

54
Q

Bacterial growth curves - Decline phase

A

More organisms are dying than are being produced by binary fission. This is due to exhaustion of the food supply and build up of toxic waste

55
Q

What is the growth rate?

A

the increase in cell numbers over a measured period of time

56
Q

What is generation time and when does bacteria usually multiply?

A
  • Time taken for a bacterial population to double in number
  • doubles every generation
57
Q

What are dilution factors?

A

A way of expressing as a ratio the volume of the original bacterial solution in the final diluted solution

58
Q

what methods can be used to measure growth?

A
  • viable count
  • total count
59
Q

What do viable count include?

A

only counting living cells capable of dividing

60
Q

What do the total count involve?

A

Counts all cells in a culture whether dead or alive

61
Q

How do you calculate how much stock solution is needed (dilution factors)

A

volume of final solution / dilution factor

62
Q

What are serial dilutions?

A

is the repeated step by step dilution of a bacterial culture. The dilution factor at each stage is usually kept constant.

63
Q

What is the purpose of serial dilutions?

A

allow highly concentrated bacterial samples to be more easily counted

64
Q

What are viable counts?

A
  • a known volume of culture is serially diluted
  • each dilution is grown on sterile nutrient agar
  • plates are made in triplicate
  • each colony produced after incubation has arisen from a single microorganism so the number of microorganisms in the original sample can be calculated
65
Q

Why are the viable count plates in triplicate?

A

To get the minimum amount of bacteria for the mean and to check for anomalies

66
Q

What are the methods of doing total counts?

A

haemocytometer
turbidimetry

67
Q

What is a Haemocytometer, how is it used?

A
  • This is a special microscope slide with a very fine grid scored in the centre.
  • A cover slide is added to the slide then a drop of the sample is placed on the slide and placed under the microscopes.
  • the number of microorganisms in several squares are counted and an average found
68
Q

Why is dye used in the haemocytometer?

A

to be able to distinguish between dead and alive cells.
The dead cells appear blue because the dye moves into the membrane.

69
Q

What is the size of the squares inside the centre square in the haemocytometer?

A

0.2mm by 0.2 mm

70
Q

What is the size of the whole centre square in the haemocytometer?

A

1mm x 1mm

71
Q

What is the depth of the haemocytometer?

A

0.1mm deep

72
Q

What is the north west rule for counting cells?

A

only count cells which overlap the lines on the top and left NOT the bottom or right

Applications for biology (5 decks)

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