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worlds of microbes > working with microbes > Flashcards

working with microbes Flashcards

1
Q

What does aseptic technique mean?

A

Without microorganisms

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2
Q

Why use aseptic techniques?

A
  • Prevention of contamination of the laboratory by the organisms being handled
  • prevention of contamination of the work with organisms from the environment
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3
Q

What does aseptic techniques do?

A
  • remove or kill microorganisms from hands, equipment and objects
  • employ sterile instruments and other items
  • remove risk of contamination of experiments, enviro and people by microorganisms
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4
Q

what is autoclaving

A

pressurised steam steriliser

-autoclave conditions-121 degrees, 15psi, 15 mins

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5
Q

what is autoclaving used to sterilise

A

-bacteriological culture media
•Glassware
•Equipment e.g. pipette tips

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6
Q

name 3 physical ways of sterilisation

A
  • heat sterilisation (dry or moist)
  • filtration (asbestoses, membrane, sintered glass)
  • radiation sterilisation (ionising or non ionising)
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7
Q

dry and moist sterilisation in heat sterilisation

A
  • moist heat sterilisation e.g. autoclave, boiling water, water heating, pasteurisation, pressurised steam
  • dry heat sterilisation e.g. dry oven, incineration
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8
Q

ionising and non ionising in radiation sterilisation

A

-ionising- x rays, U.V rays, cathode

non ionising- ultra violet

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9
Q

name two chemical ways of sterililsation

A

gas and liquid

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10
Q

name 2 gas ways of sterilisation

A
  • formaldehyde

- ethylene oxide

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11
Q

Name 4 liquid ways of sterilisation

A

alcohol
Halogens
Phenols
Aldehydes

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12
Q

How do we know that what we have autoclaved is sterile

A

1) autoclave tape has strips which change colour when exposed to 121 degrees
2) the change in colour is permanent so in the lab you will know which equipment is sterilised
3) indicator valves also can be used to assess successful autoclaving

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13
Q

What is pasteurization

A

A carefully controlled heating to reduce microbial load and it is associated with milk
It is developed to kill pathogenic microorganisms but it’s not sterilisation coz it doesnf kill all organisms.
The milk is passed through a head exchanger at 71c for 15s and cooled rapidly

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14
Q

Types of radiation

A

Microwaves, ultraviolet, xrays, gamma Ray’s and electrons as well as heat is a form of energy

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15
Q

ionizing radiation used for which pre packed plastic equip

A

Petri dishes
Spreaders
Syringes
(Use one and dispose)

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16
Q

What is ionizing radiation

A

Energy to produce ions from other molecules

It can generate hydroxyl group (OH•) and hydride(H•)

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17
Q

What does ionizing radiation do

A

It causes damage to the DNA and other macro molecules-call death
And uses electron beams, x-ray machines and radioactive elements Co OR Cs to do so

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18
Q

What can depth filters be made of and what are they

A

They are a mesh of material overlapping in a random network and can be made up of paper or glass

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19
Q

What can filtration be used for

A

Liquid or airflow
Liquids- resist clogging so can remove large particulates
Airflow- HEPA filters

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20
Q

What is membrane filtration and what is it made off

A

It is a type of liquid sterilisation and is made up of hugh strength polymers such as nitro cellulose

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21
Q

What does membrane filtration act like so what do they do

A

Act like a sieve so trap microorganisms on the filter

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22
Q

What is chemical sterilisation used for

A

To sterilise surfaces e.g. 2% Trigene

23
Q

Where are microbes grown ( bacteria/fungi)

A

Grown in either liquid or solid media
Solid media- called agar
Liquid media- called broth
And can be grown in petri dishes or plastic/ glass bottles

24
Q

What is culture media

A

Mixture of nutrients in solution
Contains nutrients by microbes grown in lab
Contain buffer to maintain pH value
Liquid(broth) or solid(agar)

25
Q

What is agar and what is it used to make

A

It is a red algae polysacharide and is used to make solid media

26
Q

How to use agar

A

Ads 1.5-2% agar to broth and boil to dissolve agar
Remains solid over incubation conditions 0-80 degrees and then compare with gelatin
It liquifies at approx 100 degrees and gels at approx 42 degrees

27
Q

How does plate culture work

A

Spread sample over agar surface
Bacteria grows on surface
Sample places in plate and agar poured over it
Bacteria grow within the agar
Plates inverted before incubation and prevents condensation falling into plate

28
Q

What is defined media

A

It is the precise amount of nutrients I.e exact chemical composition
And Highly purified inorganic salts and organic chemicals e.g. glucose and amino acids

29
Q

What is complex media

A

Rich in nutrients
Chemically undefined (milk protein ,beef,yeast, soybeans)
Support growth of microbes

30
Q

What is media formulated to be

A

General
Selective
Differential
Enrichment

31
Q

What is general formulation and what materials does it use

A

Grow wide variety of bacteria

It used nutrient agar, yeast extract, meat extract, blood agar

32
Q

What does selective media include

A

Salt
Bile
Dyes e.g. crystal violet, malachite green
Antibiotics e.g. penicillin, streptomycin
Other chemicals

33
Q

What does staphylovoccus use (media)

A

Nutrient agar +7.5% NaCl
Sodium deoxycholate which is used to inhibit gram postive skin bacteria in hand washing trials e.g. allows E coli k12 to grow

34
Q

What is mannitol salt agar used for

A

Media for the isolation of pathogenic staphylococci

35
Q

What is the ph indicator in mannitol salt agar

A

Phenol red

36
Q

What does coagulase postive and negative staphylococci produce

A

C positive s - produce yellow colonies due to mannitol fermentation
C negative s - produce small pink or red colonies

37
Q

Differential media

A

Used to distinguish between one group and another
Contains a chemical that is altered or utilised by certain microbes and not by others
It is a form of biochemical test

38
Q

Chromagenic media

A 
Contains substrates linked to chromogen (flurogen)
Enzyme substrates (ONPG, CPRG, MUG) are organisms specific 
Results in colour change or flureosense under UV light
39
Q

Oxide UTI media

A

Two chromogens cleared by the B galactosidase and B glucosidase
B gala… activity of E coli results in pink red colonies
B glu.. activity of enterococci produces blue colonies
Tryptophan deaminase activity produces a brown halo around colonies such as proteus sp

40
Q

What is enrichment media

A

Used to increase growth of particular microbe and inbit growth of others
Used when organism is slow growing

41
Q

What does enrichment media rely on

A

Selective agent
Specific nutrient
Environmental conditions e.g. light and temp

42
Q

Example of enrichment media

A

Campylobacter
C jejuni present in food in low number and causes food poisoning
Need to enrich bacteria first can take several days
Enrich using Bolton broth at 37 degrees, 4-6 hours, 41.5 degrees for 44 hours
Incubate microaerobic at 41.5 degrees for 44 hours

43
Q

What are the incubation temp generally for pathogens

A

30 to 45 degrees

44
Q

Atmospheres for incubation

A

Aerobic
Anaerobic
Microaerophilic

45
Q

Microaerophilic/ aerobic incubation

A

Optimal growth conditions: 3 to 5% oxygen, 2 to 10% carbon dioxide
Anaerobic need free oxygen enviro

46
Q

Ways of counting bacteria

A

Direct count
Indirect methods
Viable count

47
Q

Direct count

A

Number of cells are counted directly using microscope and chamber
Numbers in known volume of culture is counted and then multiplied
This is better for large cells e.g. yeast, fungal spores

48
Q

Viable count

A

Way of assessing growth of single celled organisms such as bacteria is the viable count
Bacteria are grown on agar plate

49
Q

Plate count

A

Each colony formed from single bacteria

Count number of colonies you can determine number of bacteria present

50
Q

What is Dilutions used for

A

Sample with too many colonies can be diluted to ensure plates are countable. We need a plate between 30 and 300 colonies

51
Q

How does membrane filtration methods work

A

Membrane filter on a filter support
Water sample filtered through membrane filter 0.45 um
Membrane filter removed and places in plate containing the appropriate medium
Incubation for 24 hours
Typical colonies count etc

52
Q

What is membrane filter method useful for

A

Analysing aquatic samples or low number of organisms

And it can be combined with direct counting via fluorescent dyes

53
Q

What are Contact plates used for and how does it work

A

Used to fount number of bacteria present on surface
Good for low numbers
Plate places on surface and incubated then counted

worlds of microbes (5 decks)

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