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Unit 3 Biology > Microbiology 3.4 > Flashcards

Microbiology 3.4 Flashcards

1
Q

what are the 4 steps of gram staining?

A
  1. Crystal violet
  2. Treatment with iodine
  3. Decolorisation with alcohol
  4. Counter stain with safranin
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2
Q

What determines the difference in a gram positive and gram negative stain

A

the structure of the cell wall

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3
Q

what are the three layers of a gram positive bacteria

A
  1. cytoplasm
  2. cell membrane
  3. peptidoglycan
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4
Q

How would you describe the peptidoglycan layer in a gram positive bacteria

A

thick

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5
Q

give 3 ways that you could distinguish between types of bacteria

A
  1. size
  2. shape
  3. staining characteristics
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6
Q

what is a metabolic feature

A

chemical reactions

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7
Q

what is an antigenic feature

A

surface markers

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8
Q

what is genetic features

A

different genetic features by classification

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9
Q

what determines the shape of a bacteria

A

cell wall

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10
Q

what makes up the cell wall

A

DNA

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11
Q

what 2 names can be given to the chemical whose rigid 3D mesh gives the bacterial cell wall its structure

A

peptidoglycan/ murein

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12
Q

why does gram positive bacteria stay purple through gram stain

A

because of the thick peptidoglycan layer

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13
Q

why is it medically important to know if a bacterium is gram positive or gram negative

A

to know how to treat it, they are treated differently

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14
Q

what does the stage of decolorisation with alcohol do to gram negative

A

dissolves lippopolysaccharide layer, goes colourless

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15
Q

what does counter stain with safranin do to gram negative

A

stains thin peptidoglycan layer red

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16
Q

what are the 3 shapes of bacteria

A
  1. cocci
  2. bacilli
  3. spirilli
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17
Q

what shape is cocci bacteria

A

spherical

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18
Q

what shape is bacilli bacteria

A

rod shaped

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19
Q

what shape is spirilli bacteria

A

spiral shaped

20
Q

what are the 5 necessary conditions for bacterial growth

A
  1. nutrients
  2. water
  3. oxygen
  4. temperature
  5. pH
21
Q

what are the 3 nutrients for bacterial growth

A
  1. nitrogen
  2. glucose
  3. carbon compounds
22
Q

why is nitrogen so important for bacterial growth

A

nitrogen- amino acids - proteins - growth

23
Q

what is an obligate aerobe

A

bacteria that grows only when oxygen is present

24
Q

what is an obligate anaerobe

A

bacteria that only grows without oxygen present

25
what is a facultative anaerobe
bacteria that grows with or without oxygen but prefers with
26
what does the term ‘aseptic’ mean
without bacteria
27
give 2 reasons why aseptic techniques are used during microbiology experiments
1. avoid pathogenic bacteria growing 2. avoid infection
28
give 3 ways in which equipment can be sterilised prior to experiments
1. bunsen burner 2. sterile wipes 3. autoclave
29
what pH does pathogenic bacteria grow at
pH 7 or lower
30
what pH does bacteria grow best at
pH5 - pH7.5
31
what is an example of an obligate anaerobe
E.coli because there is no oxygen in the gut
32
why is bacteria kept at 25 degrees in experiments
pathogenic bacteria cannot grow at this temperature
33
what is variable count
only counts living things
34
what is the total count
counts living and dead
35
what assumptions are made when using viable count
that each colony is 1 bacterium
36
how is total count measured
haemocytometry
37
what’s a disadvantage of total count
numbers may be overestimated
38
how do you measure viable count
dilution plating
39
what’s a disadvantage of viable count
numbers may be underestimated
40
what is serial dilution
progressively diluting something down by a known amount
41
what are 3 things you need to know in order to know how many bacteria are present
1. colony number 2. dilution factor 3. volume of sample
42
what is the equation for dilution factor
total vol in tube divided by vol added to tube
43
what is the lag phase
- protein synthesis - DNA replication - steady growth - death same as produced
44
what is log phase
- max cell division - growth doubles - cells produced= more than deaths
45
what is stationary phase
- carrying capacity phase - cells dying and produced are equal
46
what is death phase
- more cells die than produced - carrying capacity exceeded
47
what are the 3 differences that gram negative have in their cell walls that gram positive don’t
1. thin peptidoglycan layer 2. absence of proteins 3. lippopolysaccharide layer

Unit 3 Biology (4 decks)

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