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Microbiology > bacteria and disease/ bacterial DNA > Flashcards

bacteria and disease/ bacterial DNA Flashcards

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Biology 101 flashcards
1
Q

most microorganisms are

A

benign

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2
Q

normal microbial flora

A

microorganisms usually found associated with human body tissue

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3
Q

bacteria in the skin is usually found in

A

hair follicle and sweat gland–> majority gram positive step and staph.

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4
Q

many bacteria in oral cavity are

A

anaerobic due to the thickness of the plaque restricting oxygen

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5
Q

which microorganisms cause disease

A

virus’, bacteria, fungi, protozoa

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6
Q

viruses

A

influenze, lassa fever, aids

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7
Q

bacteria

A

diphtheria, TB , anthrax

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8
Q

fungi

A

candidiasis

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9
Q

protozoa

A

malaria, sleeping sickness

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10
Q

pathogenicity describes

A

the way in which the microorganism causes disease

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11
Q

virulence

A

severity of harmfulness of disease

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12
Q

example of low virulence

A

common cold, salmonella food poisoning

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13
Q

examples of high virulence

A

malaria, anthrax, plague, lassa fever

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14
Q

pathogen

A

a bacteria, virus, microorganism which causes disease

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15
Q

why can the definition of pathogen not be relied on too heavily

A

microbes cannot cause disease without a host- what actually kills people with diphtheria, for example, is the strong inflammatory response that the toxins trigger
- disease is one of the several outcomes between a host and pathogen

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16
Q

microbial pathogenicity

A

the biochemical mechanism whereby microorganisms cause disease

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17
Q

infection

A

a successful persistence or multiplication of pathogens on or within the host

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18
Q

disease

A

an interaction which causes significant overt damage to the host

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19
Q

there factors that influence severity of disease

A 
host
immunological status
physiological status
genetic makeup
route of infection (inhalation, skin, ingestion)
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20
Q

to cause disease a pathogen has to

A
  • colonize host tissue
  • grow within host cells
  • avoid host defence mechanisms
  • cause damage to the host
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21
Q

2 principle mechanisms that damage the host

A
  • they produce effectors which damage host tissues

- they produce immune responses which cause damage

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22
Q

toxins as effectors

A

exotoxins

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23
Q

neurotoxins

A

cause paralysis

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24
Q

enterotoxins

A

cause sickness and diarrhoea

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25
Q

cytotoxns

A

cause cell death

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26
Q

bacterial pathogens which produce toxins

A

diphtheria, anthrax, cholera, gangrene, tetanus

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27
Q

cytolytic toxins

A

damage cytoplasmic membrane

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28
Q

tentanus and tetanus toxins

A

mode of action: AB toxins- B portion binds to cell and facilitates translocation of A portion which possesses catalytic activity

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29
Q

dipheria and cholera toxins

A

toxins released extracellularly from growing bacteria and cause host cell damage. in diphtheria, bacteria releases toxins which inhibits protein synthesis, therefore killing the cell. in cholera, Vibrio cholera bacteria releases a toxin that enter the cell and activates the enzyme adenyl cyclase.

Both of these are AB toxins, which have two fragments, one with is responsible for cell entry and the other which is catalytically activated

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30
Q

which toxin is responsible for cell entry

A

B- binds tot he cell and facilities translocation of A

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31
Q

which toxin is catalytically active

A

A

32
Q

what is an infectious dose

A

differs between pathogens

33
Q

infectious dose

A

the infectious dose for 50% of the population

34
Q

infectious dose for bacillus anthracis

A

10,000 spores- inhaled

35
Q

infectious dose for cholera

A

10^6- ingested in water

36
Q

infectious dose for Mycobacterium tuberculosis

A

50- inhaled

37
Q

bacterial genomes structure

A

base pairs are H ended. Duplex forms a double helix. Ends are 5’ or 3’

38
Q

bacteria have relatively

A

small genomes in comparison to algae and vertebrates. smaller than some viruses and mitochondria and much smaller than eukaryotes

39
Q

genes are densely packed with no

A

introns

40
Q

operons

A

genes with related functions groups

41
Q

average gene approx

A

1kb

42
Q

protein approx

A

300 amin acids

43
Q

transcription and translation is

A

coupled and it occurs in the same compartment

44
Q

bacterial chromosomes typically

A

2000-8000 kph in size

45
Q

how many chromosomes per bacteria

A

1 per cell, can be 2

46
Q

plasmids

A

replicate independently and are not always present. 10-200kbp

47
Q

episome

A

plasmids can become integrated into the chromosomal DNA

48
Q

plasmids are less than 5% of the size of

A

the chromosome and vary in copy number

49
Q

plasmids are classed into

A

incompatibility groups based on replication control or partitioning functions

50
Q

examples of phenotypes conferred by plasmids in prokaryotes

A

antibiotic production, conjugation, metabolic functions, resistance, virulence

51
Q

conjugation (horizontal transmission)

A
  • cell to cell contact
  • plasmid encoded mechanism
  • conjugative plasmids
52
Q

process of conjugation

A
  • F plasmid in F+ donor cell
  • pilus forms with F- cell
  • pilus retracts
  • cell pair stabilised an F plasmid nicked in one strand
  • transfer of one strand from F+ cell to F- cell. F plasmid simultaneously replicated into F+ cell-synthesis of complement strand begins
  • completion of DNA transfer and synthesis
  • cells seperate
53
Q

what does conjugation require

A

DNA synthesis, rolling circle replication and initiated by the ‘nicking’ enzyme Tral

54
Q

integration of F and chromosome mobilization

A
  • recombination between similar sequences
  • cells with an integrated F plasmid are called Hfr
  • then conjugation occurs with an F- cell, therefore now F- cell has plasmid DNA too
55
Q

2 forms of bacterial replication

A

bi-directional and rolling circle replication

56
Q

Bi direction replication

A

occurs during cell division and during replication of some plasmids

57
Q

rolling circle replication

A

occurs during replication of some plasmid and during conjugation

58
Q

2 types of gene transfer in bacteria

A

horizontal and vertical

59
Q

natural transformation

A

1 Competence- extracellular binding
2 Uptake - conversion to single stranded DNA –stabilization
3 Integration- homologous recombination

60
Q

who did a key experiment on natural transformation

A

avery - involved mice

61
Q

transduction

A

1) Generalized: donor DNA from any part of the donor can be transferred
2) Specialized: specific DNA region of donor transferred. Can replicate in recipient cell

62
Q

theta- form replication

A

bi-direction–> forms two new circular DNAs

63
Q

DNA polymerise

A

copies DNA in the 5’ to 3’ direction. semi-conservative

64
Q

rate at which DNA polymerase copies DNA

A

1000 nucleotides /sec

65
Q

complete E.coli genome replicated

A

in 40 mins

66
Q

at the replication fork: leading strand

A
  • helicase separates the DNA strands.

- DNA polymerase attaches to a free 3-OH group and extends from an RNA primer in the 5’ to 3’ direction

67
Q

lagging strand

A
  • primase (syntheses RNA primers) attaches
  • DNA polymerase can then synthesise on from this RNA primer
  • then individual okazawki fragments are joined back together by DNA ligase
68
Q

natural transformation and competency

A

bacteria is competent if it can take if it can take up DNA

69
Q

what makes a bacteria competent and able to take up DNA

A

must have certain proteins on its cell surface

70
Q

integration of plasmid and chromosome occurs via

A

homologous recombination

71
Q

bidirectional replication occurs

A

during cell division

72
Q

bidirectional replication also known as

A

theta form

73
Q

nucleotides are alway addd not

A

3’ end

74
Q

when helicase unwinds DNA, pressure is put on the DNA further down, what relieves this

A

topoisomerase

75
Q

I.S. stands for

A

insertion sequence

76
Q

insertion sequence

A

where DNA has been integrated into the genome

Microbiology (25 decks)

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