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Microbiology > bacteria and disease/ bacterial DNA > Flashcards

bacteria and disease/ bacterial DNA 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
cytotoxns
cause cell death
26
bacterial pathogens which produce toxins
diphtheria, anthrax, cholera, gangrene, tetanus
27
cytolytic toxins
damage cytoplasmic membrane
28
tentanus and tetanus toxins
mode of action: AB toxins- B portion binds to cell and facilitates translocation of A portion which possesses catalytic activity
29
dipheria and cholera toxins
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
30
which toxin is responsible for cell entry
B- binds tot he cell and facilities translocation of A
31
which toxin is catalytically active
A
32
what is an infectious dose
differs between pathogens
33
infectious dose
the infectious dose for 50% of the population
34
infectious dose for bacillus anthracis
10,000 spores- inhaled
35
infectious dose for cholera
10^6- ingested in water
36
infectious dose for Mycobacterium tuberculosis
50- inhaled
37
bacterial genomes structure
base pairs are H ended. Duplex forms a double helix. Ends are 5' or 3'
38
bacteria have relatively
small genomes in comparison to algae and vertebrates. smaller than some viruses and mitochondria and much smaller than eukaryotes
39
genes are densely packed with no
introns
40
operons
genes with related functions groups
41
average gene approx
1kb
42
protein approx
300 amin acids
43
transcription and translation is
coupled and it occurs in the same compartment
44
bacterial chromosomes typically
2000-8000 kph in size
45
how many chromosomes per bacteria
1 per cell, can be 2
46
plasmids
replicate independently and are not always present. 10-200kbp
47
episome
plasmids can become integrated into the chromosomal DNA
48
plasmids are less than 5% of the size of
the chromosome and vary in copy number
49
plasmids are classed into
incompatibility groups based on replication control or partitioning functions
50
examples of phenotypes conferred by plasmids in prokaryotes
antibiotic production, conjugation, metabolic functions, resistance, virulence
51
conjugation (horizontal transmission)
- cell to cell contact - plasmid encoded mechanism - conjugative plasmids
52
process of conjugation
- 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
what does conjugation require
DNA synthesis, rolling circle replication and initiated by the 'nicking' enzyme Tral
54
integration of F and chromosome mobilization
- 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
2 forms of bacterial replication
bi-directional and rolling circle replication
56
Bi direction replication
occurs during cell division and during replication of some plasmids
57
rolling circle replication
occurs during replication of some plasmid and during conjugation
58
2 types of gene transfer in bacteria
horizontal and vertical
59
natural transformation
1 Competence- extracellular binding 2 Uptake - conversion to single stranded DNA –stabilization 3 Integration- homologous recombination
60
who did a key experiment on natural transformation
avery - involved mice
61
transduction
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
theta- form replication
bi-direction--> forms two new circular DNAs
63
DNA polymerise
copies DNA in the 5' to 3' direction. semi-conservative
64
rate at which DNA polymerase copies DNA
1000 nucleotides /sec
65
complete E.coli genome replicated
in 40 mins
66
at the replication fork: leading strand
- 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
lagging strand
- 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
natural transformation and competency
bacteria is competent if it can take if it can take up DNA
69
what makes a bacteria competent and able to take up DNA
must have certain proteins on its cell surface
70
integration of plasmid and chromosome occurs via
homologous recombination
71
bidirectional replication occurs
during cell division
72
bidirectional replication also known as
theta form
73
nucleotides are alway addd not
3' end
74
when helicase unwinds DNA, pressure is put on the DNA further down, what relieves this
topoisomerase
75
I.S. stands for
insertion sequence
76
insertion sequence
where DNA has been integrated into the genome

Microbiology (25 decks)

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