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2a- Microbiology > Biology and classification of Bacteria > Flashcards

Biology and classification of Bacteria Flashcards

1
Q

What is a pathogen?

A

Organism that causes or is capable of causing disease

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2
Q

What is a commensal?

A

Organism which colonises the host but causes no disease in normal circumstances

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3
Q

What is an opportunist pathogen?

A

Microbe that only causes disease if host defences are compromised

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4
Q

What is virulence/pathogenicity?

A

The degree to which a given organism is pathogenic

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5
Q

What is asymptomatic carriage?

A

When a pathogen is carried harmlessly at a tissue site where it causes no disease

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6
Q

How does a commensal become an opportunist pathogen?

A

Commensals can cause disease when they escape areas where they normally reside and become opportunist pathogen

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7
Q

What colour stain do gram positive bacteria have?

A

Purple

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8
Q

What colour stain do gram negative bacteria have?

A

Pink

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9
Q

What does bacillus mean?

A

A rod

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10
Q

What does spirochaete mean?

A

Spiral rod

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11
Q

How many membranes do gram positive bacteria have?

A

1

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12
Q

How many membranes do gram negative bacteria have?

A

2

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13
Q

What is between the outer and inner membrane in gram negative bacteria?

A

lipoprotein, periplasmic space and peptidoglycan

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14
Q

What is an endotoxin?

A

component of the outer membrane of bacteria, e.g. lipopolysaccharide in gram negative bacteria only

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15
Q

What is an exotoxin?

A

secreted proteins of gram positive and gram negative bacteria
- can cause damage to host cell

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16
Q

What pH do bacteria grow between?

A

4-9

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17
Q

Which type of light can bacteria grow under?

A

UV
Can survive radiation

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18
Q

How long do viruses take to double?

A

<1 hr

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19
Q

How long does E.coli, S.aureus etc take to double?

A

20-30 mins

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20
Q

How long does fungi take to double?

A

30 mins

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21
Q

Are the actions of exotoxins specific or non-specific?

A

Specific

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22
Q

Are the actions of endotoxins specific or non-specific?

A

Non-specific

23
Q

What is the composition of exotoxins?

A

Protein

24
Q

What is the composition of endotoxins?

A

lipopolysacccharide

25
Q

What effect does heat have on exotoxins?

A

Liable to change

26
Q

What effect does heat have on endotoxins?

A

Stable

27
Q

What are exotoxins produced by?

A

Gram positive and negative bacteria

28
Q

What are endotoxins produced by?

A

Gram negative bacteria

29
Q

Can exotoxins be converted to toxoids?

A

Yes

30
Q

Can endotoxins be converted to toxoids?

A

No

31
Q

What are some examples of mutation?

A
  • Base substitution
  • Deletion
  • Insertion
  • Transfer
32
Q

What are 3 types of gene transfer?

A
  • Transformation eg via plasmid
  • Transduction eg via phage
  • Conjugation eg via sex pilus
33
Q

What are obligate intracellular bacteria?

A

grow inside cells, can’t culture normally

34
Q

What is an example of obligate intracellular bacteria?

A

Chlamydia

35
Q

What are the 2 types of bacteria that may be cultured on artificial media?

A

With and without a cell wall

36
Q

What are the 2 types of bacteria with a cell wall?

A
  1. Growing as single cells
  2. Growing as filaments
37
Q

What are the 3 groups of bacteria that grow as single cells?

A
  1. Rods
  2. Cocci
  3. Spirochaetes
38
Q

What are the 2 groups of cocci?

A
  1. Gram negative
  2. Gram positive
39
Q

What can gram negative and gram positive bacteria be further categorised into?

A

Aerobic and anaerobic

40
Q

What is N. meningitidis?

A

Aerobic gram negative cocci

41
Q

What are examples of aerobic gram negative cocci?

A

Neisseria
1. N. Meningitidis
2. N. Gonorrhoeae

42
Q

What are the 2 groups of aerobic gram positive cocci?

A

Staphylococcus
Streptococcus

43
Q

What is the main cause of lobar pneumonia?

A

S. pneumoniae

44
Q

What is s. pneumoniae?

A

Alpha-haemolytic streptococcus

45
Q

What are the 3 groups of rod bacteria?

A
  1. Gram positive
  2. Gram negative
  3. Ziehl-Neelsen stain positive
46
Q

What are an example of Ziehl-Neelsen stain positive bacteria?

A

Mycobacteria
eg. M. tuberculosis

47
Q

What is the main cause of food poisoning in the UK?

A

Campylobacter

48
Q

Describe the gram staining process

A
  1. Apply a primary stain such as crystal violet (purple) to heat fixed bacteria
  2. Add iodide which binds to crystal violet and helps fix it to the cell wall
  3. Decolourise with ethanol or acetone
  4. Counterstain with safranin (pink)
49
Q

What is the coagulase test?

A

Distinguishes S.aureus from other staphylococci – coagulase positive

50
Q

What are the 3 types of haemolysis?

A

Alpha
Beta
Gamma

51
Q

What is alpha haemolysis?

A

haemolysis causing by production of hydrogen peroxide oxidising haemoglobin –
the agar appears green

52
Q

What is beta haemolysis?

A

haemolysis results because of lysis of red blood cells by haemolysis such as Streptolysin O produced by S.pyogenes

53
Q

What is gamma haemolysis?

A

implies no haemolysis

54
Q

What is the oxidase test?

A

Tests if micro-organism contains a cytochrome oxidase – implies organism able to use
oxygen as the terminal electron acceptor

2a- Microbiology (14 decks)

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