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Z MD1 Foundation block > foundation microbiology > Flashcards

foundation microbiology Flashcards

0
Q

explain the nucleoid of bacteria

A
  • no nuclear membrane
  • mostly DNA
  • single, circular closed dsDNA looped and supercoiled
  • no introns or exons
  • “core” and “accessory” genome for each species
  • can acquire genes horizontally
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1
Q

what are the key components of bacteria

A
  • cytoplasmic membrane
  • matrix
  • ribosomes
  • genome
  • cell wall
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2
Q

what colour are gram positive and negative bacteria

A

positive - blue

negative - pink

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4
Q

what makes a bacteria gram positive

A

thick layer of peptidoglycan

- also contains teichoic acids (only found in Gram +ve)

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5
Q

explain the structure of peptidoglycan

A

disaccharide backbone - N-acetyl glucosamine (G) alternating with N-acetyl muramic acid (M) with its peptide chain
- linked together by pentapeptide bridge

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6
Q

what makes a bacteria gram negative

A
  • outer membrane with lipopolysacchardies

- only thin layer of peptidoglycan

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7
Q

what is the major advantage of being a gram negative bacteria

A

the outer membrane prevents entry of bile salts, and some antibiotics

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8
Q

what is the significance of the LPS in gram negative bacteria

A

acts as an endotoxin (PAMP) - potent stimulator of innate immune system

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9
Q

explain the structure of the layers of a gram negative wall

A

from inner to outer:

  • plasma membrane
  • periplasmic SPACE with peptidoglycan
  • outer membrane with LPS
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10
Q

explain the structure of LPS

A
  • lipid head
  • core polysacchardie
  • chains of repeating peptide (O-ANTIGEN)
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11
Q

explain the wall of an Acid fast bacteria

A
  • has peptidoglycan base layer

- then additional layers of arabinogalactan, mycolic acid and lipid

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12
Q

what is the advantage of having an acid-fast wall

A

confers resistance to drying and many harsh chemicals and antibiotics

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13
Q

what is the disadvantage of having an acid-fast wall

A

slow rate of nutrient uptake = slow growth

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14
Q

function of flagella

A

motility

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15
Q

how do we serotype E coli

A

using their O and H antigens
O antigen - LPS
H antigen - on flagellum

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16
Q

function of pili (fimbriae)

A

attachment to other cells and each other

- sex pili involved in the transfer of plasmids between bacteria

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17
Q

where are pili found

A
  • on most gram -ve and only some gram +ve
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18
Q

what is a bacterial capsule made of

A

polysacchardie

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19
Q

functions of bacterial capsules

A
  • protection against dehydration
  • contribute to its virulence
  • protects against phagocytosis
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20
Q

spores are resistant to what

A
  • heat
  • desiccation
  • UV
  • many chemicals
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21
Q

bacteria replicate by..

A

binary fission

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22
Q

what are the 3 phases of the bacterial growth curve

A
  • lag phase - getting used to the environment
  • exponential phase - exponential growth
  • stationary phase - used up the nutrients and growth slows down
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23
Q

what is a facultative anaerobe

A

grows with or without air

24
Q

what is an aerotolerant anaerobe

A

survives in oxygen (not killed, but cannot grow)

25
Q

what is a microaerophile

A

grows best in low concs of oxygen

26
Q

what are the current techniques used to identify medically important bacteria (8)

A
  • microscopy
  • culture
  • proteomics
  • genomics
  • detection of structural antigens
  • susceptibility to bacteriophages and bacteriocins
  • production of toxins and other virulence determinants
  • pathogenicity for animals
27
Q

what are the 4 major components of viruses

A

genome
matrix
capsule
envelope

28
Q

how does a virus acquire an envelope

A

acquired from budding from the host cell

29
Q

what is a viral capusle

A

a protein shell

30
Q

what are the two major structures of viral capsids

A

icosahedral

helical (associated with envelope for support)

31
Q

which virus does not have a helical or icosahedral capsule

A

poxvirus - has complex symmetry

32
Q

what is the function of a viral capsule

A

protects from breakdown by nucleases

33
Q

which virus has multiple capsules

A

rotavirus - makes it very hardy

34
Q

all helical viruses are DNA or RNA

A

RNA

35
Q

all RNA viruses have …

A

an envelope

36
Q

what are the methods of viral detection

A
  • direct visualisation by electron microscopy
  • viral gene detection
  • host serological responses
  • viral antigen detection
  • viral cultivation (gold standard)
37
Q

what is the virus that caused SARS

A

coronavirus

38
Q

where did the virus come from that caused SARS

A

civil cats

39
Q

what is a virus

A

subcellular genetic elements that are obligate parasites

40
Q

what is a viral envelope composed of

A

lipid with glycoproteins embedded

41
Q

what are the 3 steps to make a specific diagnosis of infection

A
  1. demonstrate organism, compound or product
  2. isolate organism
  3. demonstrate a serological response
42
Q

what are the 4 techniques in which you can demonstrate an organism

A
  • microscopy
  • antigen detection
  • nucleic acid detection
  • mass spec
43
Q

what techniques are used for antigen detection

A
  • latex agglutination
  • solid phase assay
  • capture assay
44
Q

explain how latex agglutination works

A
  • antigen is in solution
  • latex particles are coated with known antibody
  • cross linking of the latex particles when antibody bound to antigen = agglutination
45
Q

explain how solid phase assay works

A
  • antigen in solid phase

- known labelled Ab binds and gives result

46
Q

explain how capture assay works

A
  • 1st Ab on the solid phase
  • antigen introduced and binds
  • 2nd antigen (labelled) introduced and binds to antigen –> result
47
Q

what are the two types of nucleic acid detection

A

hybridisation

PCR

48
Q

what are the 4 ways you can demonstrate a serological response to an organism

A
  • Tube agglutination test
  • solid phase assay
  • Western blot
  • rising titre/specific IgM
49
Q

for bacteria to cause infection of mucosal surfaces.. what does it have to do

A
  • overcome competition by commensals
  • move through mucus
  • resist mucosal defences
  • adhere to epithelial cells
50
Q

what are the attributes of a bacterial pathogen

A
  • adhesion
  • colonisation
  • penetration
  • multiplication
  • tissue damage
51
Q

how do bacteria penetrate epithelial cells

A

via pathogen-mediated endocytosis

52
Q

what two things must bacteria do to evade immune system removal

A
  • evade phagocytosis (EC)

- resist killing (IC)

53
Q

how can bacteria evade phagocytosis

A 
direct effects on phagocytes
- production of leukocidins
- anti inflammatory toxins and enzymes
- surface anti-phagocytic structures
interfering with opsonins
- C'
- Ab
54
Q

how can bacteria resist IC killing

A
  • inhibit respiratory burst
  • prevent phagolysosome formation
  • escape from the phagocytic vacuole
  • resist bactericidal systems
55
Q

how do capsules enhance virulence

A
  • electrostatic repulsion
  • resemble host components
  • mask underlying structures
  • -> unable to be opsonized by C’
  • -> can be opsonized by Ab
56
Q

what techniques do bacteria have to evade adaptive immunity

A
  • direct immunosupression
  • expression of weak antigens
  • antigenic diversity
  • antigen modification
57
Q

which bacteria modifies its antigen to evade the immune system

A

salmonella

Z MD1 Foundation block (7 decks)

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