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IPM > Paul Wade: Medical Microbiology > Flashcards

Paul Wade: Medical Microbiology Flashcards

(49 cards)

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1
Q

What is archae?

A

Type of prokaryote, found in extreme environments.

They have different cell wall and lipid components and ribosomal RNA sequences to bacteria

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2
Q

What is the difference between eukayrotic and prokaryotic cells?

A

Prokaryotic cells do not have an ER, golgi apparatus, mitochondria, nucelus or lysosome

Prokaryotic cells only possess a single circular chromosome.

Prokaryotic ribosomes are 70s (their units are 50s and 30s) whereas eukaryotic ribosomes are 80s (their units are 40s and 60s)

Prokaryotic membranes do not contain sterols e.g. cholesterol

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3
Q

In what ways can you classify and identify bacteria?

A
  • Biochemical classification- statistical analysis of ~ 50 physical and chemical characteristics
  • DNA composition- calculating mol % of DNA bases
  • DNA homology- extent to which DNA sequences vary, measured by genome sequence and sequence typing
  • 16s RNA sequencing
  • Chemical composition- MALDI-TOF for rapid diagnostics:
    Matrix Assisted Laser Desorption Ionisation Time- Time of Flight
    Applies mass spec and see how long it takes for sample to hit the signal which is a quicker method than growing the organism
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4
Q

What is the difference between gram -ve and gram +ve bacteria?

A

Gram +ve:

  • Thick cell wall
  • More peptidoglycan that retains the stain
  • Lipoteichoic acids transversing wall and anchored in membrane

Gram -ve:

  • Tiny amount of bacterial cell wall
  • Thin peptidoglycan layer
  • Contains porins and lipid A
  • Pores allow certain molecules through
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5
Q

What are ribosomes made from?

A

rRNA and protein

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6
Q

What does the ribosome consist of?

A

Small 30s subunit binds mRNA

Large 50s subunit has binding sites for two tRNAs

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7
Q

What is transcription?

A
  • Genetic code from DNA to mRNA via RNA polymerase
  • Correct sequence of bases for polypeptide is found on + DNA
  • mRNA copy is taken from -DNA strand to form + RNA
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8
Q

How is a mutation induced?

A
  • UV radiation which causes covalent cross-links between adjacent pyrimidines (causing deletions)
  • Ionising radiation causes hydrolysis of phosphodiester backbone and cannot repair itself causing deletions or insertions
  • Nitrous acid deaminates A and C forming uracil and hypoxanthine from adenine). Will carry substitution mutations as hypoxanthine will pair with C and not T

GC to AT and AT to GC

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9
Q

Are bacteria haploid or diploid?

A

Haploid so have no homologous chromosome to mask the effect of mutation

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10
Q

How can drug resistance occur other than mutations?

A

Genetic recombination via horizontal gene transfer via transduction/conjugation/transformation

Cannot occur through sexual production as bacteria progeny are clones

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11
Q

What are T-phages?

A

Infect host bacteria via injectin of their DNA through their baseplate and contractile tail

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12
Q

What are bacteriophages?

A

Viruses that infect bacteria

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13
Q

What are the two types of phage injection?

A
  1. Virulent (lysis of host cell)

2. Temperate (lysogeny)

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14
Q

what is the bacteriophage lytic cycle?

A
  1. Mature virion injects onto the host cell and its viral coded enzymes degrade host DNA.
  2. Replication of viral DNA and protein takes place
  3. New virions are assembled within the host cell
  4. Host cell is lysed and virions are released
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15
Q

What is the bacteriophage lysogenic cycle?

A
  1. Mature virion injects onto the host cell, penetrates and injects DNA
  2. Viral DNA circularises and is incorporated into the host genome
  3. Viral genome produces an inhibitor cI which inhibits lytic cycle
  4. Under stress, cro protein induces lytic cycle and new virions are assembled
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16
Q

Summarise lysogenic conversion

A
  1. Incorporation of lysogenic
    (temperate) phages into bacterial chromosomes sometimes results in
    expression of phage genes.
  2. These may act as toxins when expressed

Examples:

  • Infection of E. coli by phage
    λ leads to production of a toxin causing haemorrhagic diarrhoea
  • Infection of Vibrio cholerae by CTX phage, results in cholera toxin secretion.
  • Infection of C. botulinum by
    clostridial phages cause botox
    secretion
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17
Q

Summarise conjugation

A
  • Occurs between opposite mating types (F+ forms attachment pilus and a conjugation tube to join with F-)
  • Plasmids are transferred in this way and they both become F+
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18
Q

Summarise transformation

A
  • Exogenous DNA uptake
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19
Q

What is the difference between autotrophs and heterotrophs

A

Autotroph - organism that needs hydrogen to reduced CO2 to CH2O

Heterotroph- organism that obtains hydrogen from organic molecules

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20
Q

Is oxygen toxic to anaerobes?

21
Q

What are sources of macronutrients?

Study These Flashcards
A
  • carbon (backbone for molecules)
  • Hydrogen
  • Nitrogen (amino acids)
  • Sulphur
  • Phosphorus (production of ATP)
  • Oxygen (synthesis of organic molecules and a terminal electron acceptor in aerobes)
22
Q

What is an oligate aerobe?

Study These Flashcards
A

dependent on oxygen for growth e.g.) TB. Migrates to top of test tube

23
Q

What is an obligate anaerobe?

Study These Flashcards
A

dies in oxygen presence (clostridium). At the bottom of the test tube

24
Q

What is a facultative anaerobe?

Study These Flashcards
A

does not require oxygen for growth but grows better in its presence (E.coli) More at the top but spread throughout test tube

25
What is an aerotolerant anaerobe?
Grows equally well in presence and absence of oxygen (streptococcus pyogenes) Equal amounts throughout test tube
26
What is a microaerophile?
requires small amount of oxygen but damaged by atmospheric oxygen. Is more towards the top but not at the very top of the test tube
27
What are micronutrients?
``` Potassium Sodium Magnesium Iron Colbat (constituent of vitamin B12) ```
28
When is facilitated diffusion not ideal for bacteria?
Bacteria in environments with low concentration of nutrients
29
Outline active transport in bacteria
ATP hydrolysis facilitates entry Proton gradient across membrane provides energy for transport (PROTON MOTIVE FORCE)
30
What is the lag phase of bacterial growth?
``` • Adaptation to medium. • Little increase in cell numbers. • Cells are metabolically active. • Increase in production of ATP. • Increased biosynthesis. ```
31
What is the log phase of bacterial growth?
``` • After cells have adapted to medium, they undergo rapid cell division at regular rates, (generation time). • Population doubling each generation time. • Exponential/logarithmic growth. • Antibiotics are active against these highly metabolically active cells. ```
32
What is the stationary phase of bacterial growth?
``` • Nutrients limited. • Certain required inorganics, such as O2, decrease. • Toxic waste concentrations increase. • Cell metabolism decreases. • Population static. • Some cells may become metabolically inactive (quiescence). • Some antibiotics become ineffective. ```
33
What is the death phase of bacterial growth?
• Medium becoming less supportive. • More cells die than are being produced
34
What is the difference between primary and secondary metabolites?
``` Primary metabolites: Produced during log phase growth, products essential for cell growth; amino acids, nucleotides, lipids, CHO, proteins etc. ``` ``` Secondary metabolites: Produced at onset of stationary phase or as a result of quorum sensing; alkaloids, antibiotics, pigments, toxins, pheromones, virulence factors etc. ```
35
What is contamination?
- Transient presence of microbes - May be pathogenic/ non-pathogenic - On skin or other body surfaces - Does not lead to injury or invasion of tissues
36
What is colonisation? What is the difference between contamination and colonisation?
- Continuing presence of microbes for weeks- years - Doesn't cause injury or invasion of tissues Difference is time course
37
Microbes can fall into 3 groups - what are they?
1. Normal flora 2. Aggressive pathogens (cause disease in normal host) 3. Opportunistic pathogen (cause disease in hosts with impaired defences)
38
What is a fever?
37.4 degrees or higher
39
What is shock?
- Life-threatening condition - Hypotension and decreased tissue perfusion - Can be a consequence of sepsis - Most common in bacterial infections - Low BP, rapid HR
40
What metabolic changes are found in infection?
- Increased energy/carbohydrate metabolism - Altered metabolism of protein, fat, minerals - Changes in cytokine production IL-1, IL-6, TNF
41
Outline malnutrition in infection
- Induced by TNF production - Infection leads to malnutrition which leads to impaired host defences and further infection - Can impair host defences - skin diseases, decreased immune defences and decreased gut function
42
What role does C- reactive protein have in infection?
- Acute phase protein - Binds to protein and activates the complement pathway - Causes opsonisation and phagocytosis - Can also be raised in post op/after trauma REDUCED IN VIRAL INFECTION
43
What role does erythrocyte sedimentation rate have in infection? (ESR)
- Chronic phase response - Due to plasma protein changes - Raised in infection, and other conditions such as anaemia - Extent determines significance >100
44
What is Clostridia difficile?
Positive rod
45
What is neisseria gonorrhea and meningitidis?
Negative cocci
46
What is pseudomonas aeruginosa?
Negative rod
47
What is Escherichia Coli?
Negative rod
48
What is salmonella?
Negative rod
49
What is helicobacter?
Negative rod

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