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Nancymedsci202 > Lab 1 > Flashcards

Lab 1 Flashcards

Okay so im not sure about card 41, 42 and some other ones inthe 40's...

1
Q

List the 4 basic microbiology techniques learnt in lab 1

A

Gram stain
microscope use
streak plate
lawn plate

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2
Q

bacteria and fungi can grow in the lab if what conditions are provided for?

A

Suitable nutrients

environment favourable for growth

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3
Q

How have the fomulation of many types of culture media formed?

A

Species of bacteria and fungi differ in their requirements for suitable nutrients and favourable growth environment

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4
Q

what are the two main kinds of culture media?

A
  1. liquid

2. solidified with agar

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5
Q

what is agar?

A

gelling agent derived from seaweed which melts at 98-100degreesC

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6
Q

What conditions must the culture medium be in prior to use?

A

It must be sterilised and remain sterile prior to use

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7
Q

How are most culture media sterilised?

A

by autoclaving

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8
Q

what is autoclaving?

A

Uses steam under pressure to generate sufficient moist heat to kill both vegetative and heat or chemical resistant forms of microorganisms

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9
Q

give examples of heat or chemical resistant microorganisms

A

bacterial endospores, protozoan cysts

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10
Q

What is the pressure commonly used for autoclaving?

A

15 pounds per square inch for 15 mins.

this increases temperature of steam to 121 degrees C

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11
Q

What happens to inoculated material used in the lab before disposal?

A

they are autoclaved before disposal

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12
Q

what is the innoculum

A

microorganisms of interest (that you want to transfer onto the sterile medium)

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13
Q

What is innoculation

A

the transfer of microorganisms of interest onto the sterile medium

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14
Q

What kind of technique must be used to innoculate?

A

aseptic technique

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15
Q

why must aseptic technique be used for innoculation

A

prevents contamination by extraneous microorganisms

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16
Q

where may extraneous microorganisms be?

A

in the air, on lab equipment or surfaces or on hands of laboratory workers

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17
Q

Give another reason why aseptic technique is used

A

also helps to prevent contamination of the lab worker by the microorganims being handled

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18
Q

When does growth/division occur?

A

when a freshly inoculated culture is incubated under favourable conditions

this is 37degreesC for most human pathogens

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19
Q

How is growth of bacteria indicated by in liquid media?

A

cloudiness (turbidity)

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20
Q

how is growth of bacteria indicated by in solid media?

A

bacteria and fungi generally for colonies

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21
Q

The appearance of _______ is important in identification

A

colonies (colour, shape etc)

22
Q

Description of colonies is what kind of appearance?

A

Macroscopic appearance

23
Q

what is microscopic appearance?

A

term used to describe the appearance of cells

24
Q

give the importance of a gram stain

A

it is used to quickly begin the process of identifying the microorganism

25
Q

why are bacteria stained?

A

They are almost transparent

staining increases their visibility under the light microscope

26
Q

What must be prepared before bacteria can be stained?

A

a heat fixed smear of the bacteria

27
Q

What does staining reveal?

A

The overall shape of the bacterial cells (cocci, bacilli, vibrios, sprirlla)

the arrangement of cells (single cells, chains, pairs, clusters, tetrads)

28
Q

What characteristics are used in the identification of bacteria?

A

Characteristics of cellular morphology: size, shape and arrangement

29
Q

How do yeast cells differ from bacterial cells?

A

By size, yeast cells are eukaryotic, usually bigger

30
Q

briefly describe how to prepare a heat fixed smear

A
  1. sterilise loop, and run slide over flame a few times to sterilise slide
  2. place loopful of sterile saline on centre of slide
  3. sterilise loop
  4. For solid media: remove bacterial colony and emulsify in saline using circular motion.
  5. For broth culture: [dont need saline] invert broth a few times, take 2/3 loopfuls of broth onto slide.
  6. spread drop on the slide to size of 10c coin
  7. sterilise the loop
  8. allow smear to air dry, then heat fix smear by running through flame a few times
  9. check slides are labelled
31
Q

what is the purpose of heatfixing the smear?

A

to fix bacteria to slide
to kill microorganisms without altering their structure too much
to help microorganism adhere to slide better and take up the slide

32
Q

why is it necessary to flame sterilise inoculating loop both before and after the preparation of smear?

A

To eliminate contamination of slide preparations nad inoculum plate
so that bacteria stained and seen under microscope is the bacteria of interest

33
Q

Why is gram stain used extensively in bacteriology

A

it is valuable.

it allows the differentiation of bacteria into two large groups based on differences in cel lwall composition

34
Q

What are the two types of gram stained bacteria

A

Gram positive

gram negative

35
Q

What colour are gram positive organisms?

A

blue-violet throughout the procedure

36
Q

What colour are gram negative organisms?

A

red, form acceptance of the counterstain, safranin. The violet iodine complex is lost when washed with acetone or another solvent

37
Q

Why are yeast cells not gram positive cells even though they retain the crystal violet-iodine complex?

A

Yeast cells are eukaryotes and lack the bacterial cell wall morphology

38
Q

Name the 4 staining solutions used in gram staining

A

Crystal violet
Gram’s Iodine
Acetone/alcohol mix
Safranin

39
Q

Why is the stain with acetone the cruicial step in gram staining?

A

If the cell is over treated with acetone (i.e. destainer is left for too ong,) then even gram positive organisms will appear negative

If cell is not treated well enough with destainer, then gram negative organisms will appear positive.

Aim for 5 seconds

40
Q

Why is it necessry to stain bacterial cells?

A

Bacteria are almost transparent. Staining increases their visibility under the microscope

41
Q

What causes the specific arrangement and pattern distribution of bacterial cells?

A

Uhm… i actually dunno. LOL, the type of bacteria they are? ugh.

42
Q

Why do gram positive and gram negative bacteria stain differently?

A

Although both gram + and gram - cell walls contain peptidoglycan,

the gram + cell wall is thicker

the gram - cell wall has additional lipopolysaccharides

43
Q

Why is a four phase streak used?

A

To streak bacteria onto an agar plate in order to obtain well-separated ‘single’ colonies

from these colonies, pure cultures of the different bacteria can be isolated

44
Q

What is the value of isolating a pure culture/?

A

Clinical specimens frequently contain mixed populations of bacteria

once pure cultures are obtained, the organism implicated in an infection can be identified

treatment can then be modified if necessary

45
Q

The wire loop is heated four times during this procedure. What is the significance of each flaming

A

To eliminate bacterial growth from other colonies… ?

46
Q

When is an agar plate lawn used?

A

To test when bacteria are able to grow in the presence of anti-microbial agents

47
Q

how does the agar plate lawn work

A

anti-microbial agent is placed in the centre of a freshly spread lawn of bacteria spread on an agar plate

as bacteria grow overnight, they will cover the plate as usual, unless the agent inhibtis the growth.

if growth is inhibtied we will see a zone of inhibition

therefore it is crucial to obtain full coverage of the agar plate

48
Q

What is colony morphology used for?

A

an aid in identification as the colony morphology varies according to species

49
Q

What are the different kind of shape forms?

A

round, spindle shaped, irregular, pin point, filamentous

50
Q

What arethe different types of elevation?

A

convex, raised, dome shaped, flat, umbonate

51
Q

What are the different types of margins?

A

filamentous, lobed, erose, entire

52
Q

What other categories of colony morphology are there?

A

colour, texture, odour

Nancymedsci202 (10 decks)

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