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CELS 191 > Microbiology > Flashcards

Microbiology Flashcards

1
Q

What is the approximate size of a bacteria?

A

1 μm

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2
Q

What are the two types of cells?

A

Eukaryote and Prokaryote cells

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3
Q

What are the two kingdoms that make up Prokaryote cells?

A

Archaea

Eubacteria (bacteria)

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4
Q

Do bacteria have a nuclear envelope?

A

No

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5
Q

Do bacteria have membrane-enclosed organelles?

A

No

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6
Q

What sort of chromosomes do bacteria have?

A

A single circular chromosome

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7
Q

What are some key features of a bacterial cell? (8)

A
  • chromosomes
  • fimbriae/pili
  • nucleoid
  • ribosomes
  • plasma membrane
  • cell wall
  • capsule
  • flagella
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8
Q

What is the cell wall of a bacteria made of?

A

Peptidoglycan

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9
Q

Describe peptidoglycan and include its function

A

Rigid macromolecular layer that provides strength to the cell.
It protects the cell from the osmotic lysis (ie. water entering from the environment) and confers cells shape

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10
Q

Bacteria without a cell wall are called

A

mycoplasmas

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11
Q

Describe the structure of peptidoglycan

A

Links of alternating NAMs and NAGs attached by side-chain amino acids and cross-link amino acids

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12
Q

What is the name of the enzyme that cross-links the peptidoglycan chains to form rigid cell walls?

A

Transpeptidase

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13
Q

What is the role of transpeptidase?

A

It is the enzyme that catalyses the cross-link between the peptidoglycan chains to form rigid cell walls

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14
Q

Describe how penicillin acts to kill bacteria

A

Penicillin bonds to transpeptidase to prevent it from catalysing the cross-link between the peptidoglycan chains to form rigid cell walls. Without the cell wall, the bacteria dies very quickly

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15
Q

Describe the Gram stain procedure

A
  • acquire a mixture of two different bacteria (eg. Staphylococcus aureus and Escherichia coli) and place on a slide
  • apply crystal violet dye to stain the mixture
  • apply iodine to set the dye
  • wash with ethanol (some of the bacteria will remain purple)
  • apply safranin as a counterstain (some will be purple and some will be pink)
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16
Q

What type of bacteria remains purple after washed with the ethanol?

A

Gram-positive bacteria

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17
Q

What type of bacteria decolourises after being washed with the ethanol?

A

Gram-negative bacteria

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18
Q

Describe Gram-positive bacteria

A
  • the peptidoglycan layer is very thick

- this layer encloses the plasma membrane

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19
Q

Why does Gram-postive bacteria remain purple after being washed with the ethanol?

A

Because it has a very thick peptidoglycan layer which traps the crystal violet which masks the red dye

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20
Q

How thick is the peptidoglycan layer in a Gram-positive bacteria?

A

20 - 80 nm

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21
Q

Describe Gram-negative bacteria

A
  • the peptidoglycan layer is very thin
  • this layer encloses the plasma membrane but another layer of membrane encloses it (ie. there is the inner plasma membrane and then the cell wall which consists of the thin layer of peptidoglycan and an outer layer of plasma membrane)
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22
Q

Why does Gram-negative bacteria decolourise after being washed with the ethanol?

A

Because the layer of peptidoglycan is so thin, the crystal violet is easily rinsed away, revealing the red safranin dye.

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23
Q

How thick is the peptidoglycan layer in a Gram-negative bacteria?

A

5 - 10 nm

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24
Q

What is the function of bacterial flagella?

A

to allow some bacteria movement in a liquid medium

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25
Q

What is the diameter of a flagella?

A

10 - 20 nm

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26
Q

How many flagella, on average, are there on a bacterial cell?

A

5 - 10 per cell

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27
Q

How do flagella work?

A

They act as a propeller (the cell rotates them to move through a liquid medium)

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28
Q

What are the three major sections of a flagella?

A
  1. long filament
  2. hook
  3. basal body/basal motor
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29
Q

Describe the long filament of the flagella

A
  • it extends into the surrounding medium

- composed of subunits of a protein (flagellin)

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30
Q

Describe the hook of the flagella

A

a curved section connecting the filament to the cell surface (connect the motor)

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31
Q

Describe the basal body/basal motor of the flagella

A
  • it anchors the flagellum into the cell membrane of the bacterium by disc-shaped structures (plates/rings)
  • it sits in the cell membrane
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32
Q

What is flagella used for?

A

Chemotaxis

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33
Q

Describe the process of chemotaxis

A

the movement of bacteria along a concentration gradient towards a chemical attractant or away from a chemical repellent

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34
Q

Describe the mechanisms of chemotaxis

A
  • bacterium can’t sense the difference between the concentration at the front of the cell versus the back of the cell because they are too small
  • instead it senses the changes with time (temporal gradient)
  • the bacteria uses its sophisticated chemoreceptors to sense what the concentration is
  • then the bacteria swims off again and remeasures the gradient
  • if the concentration is going up, it keeps swimming in that direction
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35
Q

What are fimbriae?

A

hairlike structures on the outside of the bacteria

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36
Q

What is the purpose of fimbriae?

A

they have adhesive properties that cause the bacteria to stick to other surfaces

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37
Q

Fimbriae are an example of an

A

inherited trait (ie. not all bacteria have fimbriae)

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38
Q

What are other methods of gripping, apart from the fimbriae?

A

capsules and slime layers

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39
Q

Describe a capsule

A

Glycocalyx organised into a defined structure attached firmly to a cell wall

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40
Q

Describe a slime layer

A

Glycocalyx disorganised without cell shape, attached loosely to cell wall

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41
Q

What is glycocalyx?

A

A gelatinous polysaccharide outer covering. It forms a sticky meshwork of fibres.

  • if organised into a defined structure attached firmly to a cell wall, it forms a capsule.
  • if disorganised without cell shape, attached loosely to cell wall then it is a slime layer
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42
Q

What are the functions of a capsule?

A
  • virulence factors
  • adherence to cell surfaces and structures
  • prevents the cell from drying out
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43
Q

What is meant by virulence factors?

A

Protecting the bacteria from phagocytosis and engulfment by immune cells

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44
Q

When does the bacteria form endospores?

A

Under unfavourable conditions (under stress such as nutrient starvation, overcrowding)

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45
Q

What are the two bacteria that make endospores?

A

Bacillus and Clostridium

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46
Q

Bacteria reproduce by

A

asexual reproduction (ie. grow and divide into two identical daughter cells)

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47
Q

What is binary fission?

A

Asexual reproduction by a separation of the body into two new bodies.

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48
Q

Bacterial cells that form endospores divide

A

asymmetrically

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49
Q

Describe asymmetric cell division

A

When bacteria grows, one end forms a spore and the other doesn’t so a spore is growing inside the mother cell. The cells actually don’t divide, it is purely altruistic behaviour of the mother (a mature spore is just formed)

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50
Q

When the conditions are favourable, the spore will

A

germinate into a bacteria and give rise to a vegetative cell

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51
Q

What 5 things are endospores resistant to?

A

heat, harsh chemicals, antibiotics, disinfectants, radiation

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52
Q

Endospores are formed during _________ and germinate under _________

A

unfavourable conditions

favourable conditions

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53
Q

Why are prokaryotes so dominant?

A

Because they are so small and have a very fasting doubling rate which means they can evolve/adapt extremely quickly.

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54
Q

What is binary fission?

A

A type of asexual reproduction where once cell spilts into two

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55
Q

Describe the process of binary fission:

A
  • the cell replicates its chromosome
  • the parent cell now has two copies of the DNA
  • one copy goes to each end of the cell
  • the cell splits in half
  • two identical daughter cells result
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56
Q

Prokaryotes reproduce ________ by cell division through the process of ______ ________

A

asexually

binary fission

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57
Q

Because prokaryotes have been around for so long, they have extreme

A

ecological and metabolic diversity

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58
Q

What is a closed batch culture?

A
  • a form of cell culturing
  • there is limited amount of nutrients provided
  • once the nutrients has been used, the cells can not proliferate
  • growing in a closed system eg. no inflow or outflow
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59
Q

What is the purpose of closed batch culture?

A

You can see how an organism behaves under nutrient rich and nutrient poor conditions

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60
Q

What do we see in a closed batch culture?

A

A growth curve

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61
Q

What are the advantages and disadvantages of using closed batch culture?

A

Advantages:
Easy to do
Disadvantages:
Biased towards fast growing organisms like pathogens

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62
Q

What are the four stages of the growth curve?

A
  1. lag phase
  2. exponential/log phase
  3. stationary phase
  4. death phase
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63
Q

Describe what the lag phase is including what it looks like on a growth curve

A

There is a lag between adding a cell to the media and when it actually starts growing.
On the curve, this looks like a flat(ish) start to an exponential graph (positive)

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64
Q

What does the length of the lag phase depend on?

A

The history of the cell:

  • those that have been starved previously have to turn on genes and make machinery before they can grow. The longer it takes them to make this machinery, the longer the lag phase.
  • for a cell that is actively growing, the lab phase is short because it is already used to those conditions and and it knows how to take advantage of them
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65
Q

Describe what the exponential/log phase is including what it looks like on a growth curve

A
  • there is plenty of nutrients for the cell
  • they are growing and dividing at maximum capacity
  • the population is doubling in a constant time interval
  • seen as a steep increase in log of viable organisms
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66
Q

Describe the stationary phase including what it looks like on a growth curve

A
  • the organisms have started running out of nutrients
  • some of the cells in the culture have started to die
  • cells stop growing and cryptic growth is observed
  • there is a dynamic population
  • the curve flattens
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67
Q

What is cryptic growth?

A

When organisms survive by consuming the lysed cell contents of other dead cells within the culture. When a cell dies, all its nutrients gets released into the media and all the growing cells can scavenge and grow again.

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68
Q

What is a dynamic population?

A

When there is an equilibrium between growing and dying cells

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69
Q

Describe the death phase including what it looks like on a growth curve

A
  • cells die
  • the viable count declines
  • the equilibrium between growing and dying cells is skewed towards death
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70
Q

“No growth” actually means

A

death rate and growth are in balance (ie. no net growth)

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71
Q

Penicillin is an

A

antibtiotic

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72
Q

What are the only cells that penicillin and other inhibitors/antibiotics act on?

A

growing/replicating cells

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73
Q

What are persiters?

A

Cells that are not growing or replicating and are not dividing so they are insensitive to penicillin

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74
Q

Describe how persisters can lead to persistent infections without antibacterial resistance

A
  • a culture can include both actively growing (sensitive) population and not growing (insensitive) bacteria.
  • after an antibacterial treatment, the growing bacteria are killed but the insensitive bacteria remain
  • after the antibiotic is removed, there is persistent infection as the pathogen is resuscitated
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75
Q

What do prokaryotes need in order to multiply?

A
  • a carbon source
  • an energy source
  • a reducing power
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76
Q

Describe what is meant by a carbon source that prokaryotes require

A

a building block for macromolecular synthesis

ie. the bulk of the cell is made up of carbon so we need a source of carbon in order to grow a cell

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77
Q

Describe what is meant by an energy source that prokaryotes require

A

energy in the form of electrons (electricity) to drive anabolic and catabolic reactions inside the cell

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78
Q

Describe what is meant by a reducing power that prokaryotes require

A

a way to carry the electrical energy/electricity

this is usually with intermediates (such as NAD+ and NADP+) that carry electricity from one side of the cell to the other side of the cell

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79
Q

Chemical energy is stored in

A

bonds

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80
Q

Broken bonds releases _______ that can be captured in _____ _____

A

energy

new bonds

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81
Q

What is the most common energy currency?

A

ATP

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82
Q

Describe how microbes can access energy

A

Breaking bonds in glucose to release energy.
This energy has to be used to go somewhere else.
In this case, the energy is used to add a P to an ADP to form ATP.
When energy is released, you also release H which needs to be captured (by NAD+ to form NADH) and this energy can be taken to the membrane to make more energy

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83
Q

The idea of breaking and making bonds is the basis of

A

redox reactions

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84
Q

How do microbes harvest their energy?

A
  • they break down substrates into products and extract energy
  • this is a catabolic reaction
  • energy is produced in the form of ATP
  • the ATP is used to build macromolecules and other cellular constituents from monomers in a process of biosynthesis.
  • this is an anabolic reaction
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85
Q

Where are the two places that microbes can get their energy from?

A
  • light (photo)

- chemical compounds (chemo)

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86
Q

Where are the two places that microbes can get their carbon source from?

A
  • carbon dioxide (auto)

- organic compounds (hetero)

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87
Q

A compound that uses light energy to fix carbon is called?

A

Photoautotrophs

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88
Q

What is carbon fixation?

A

Producing complex carbohydrates from inorganic CO2

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89
Q

A compound that uses light energy but carbon has to be provided to them from organic compounds is called?

A

Photoheterotrophs

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90
Q

A compound that uses chemical compounds as energy to fix carbon is called?

A

Chemoautotrophs

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91
Q

A compound that uses chemical compounds as energy but carbon has to be provided to them from organic compounds is called?

A

Chemoheterotrophs

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92
Q

Why can most organisms not be isolated in pure culture?

A

Most organisms depend on other members of the community and so we can’t recreate the environment with pure cultures.

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93
Q

What is a population?

A

Groups of organisms of the same type

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94
Q

Individual microbial cells of a species proliferate and form a

A

population

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95
Q

What is a community?

A

When populations interact and communicate

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96
Q

What is the microbiome?

A

All organisms, and their genes, within a particular environment

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97
Q

What is enrichment culture?

A

Providing the temperature and chemical conditions in the laboratory that encourage the growth of specific groups of microbes.

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98
Q

Explain how an enrichment culture works

A

If you have a very diverse group of microorganisms living together, you want to get information about a specific subset of them, you can change the conditions in the lab so that only a portion of those start growing into higher numbers.

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99
Q

Enrichment cultures are an example of

A

mesocosms

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100
Q

What are mesocosms?

A

an experimental system that stimulates real-life conditions as closely as possible

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101
Q

What are the two outcomes from breaking bonds in a carbon based molecule?

A
  • harvesting energy

- harvesting building blocks

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102
Q

Energy from oxidation is shuffled through

A

an intermediate (NADH/NADPH)

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103
Q

Explain the process of ReDox reactions in bacteria

A
  • H2S is oxidised to form S
  • this releases energy and H
  • as an opposite reaction, NADP+ is reduced to form NADPH2 (capturing the H from H2S)
  • When NADPH2 is oxidised to form NADP+, H is released and energy is released
  • in an opposite reaction, the energy released is used to fix carbon (reduce CO2 to CH2O)
104
Q

ReDox in bacteria is the basis of

A

energy transfer in cells

105
Q

Autotrophs are

A

primary producers

106
Q

Heterotrophs are

A

decomposers

107
Q

Describe autotrophs

A
  • primary producers
  • fix CO2
  • self sufficient, do not require carbon
108
Q

Describe heterotrophs

A
  • decomposers
  • need fixed carbon, cannot use CO2 directly
  • dependent on primary producers
109
Q

Where can the chemical energy come from for chemotrophs?

A
  • carbon compounds (organic eg. glucose)

- non-carbon compounds (inorganic eg. H2S)

110
Q

Where does the solar energy come from for phototrophs?

A

energy from the sun

111
Q

Describe how autotrophs and heterotrophs work together to access carbon

A
  • autotrophs are primary producers which means that they can take CO2 and convert in into a complicated substrate
  • heterotrophs are decomposers which means they consume this fixed carbon and break it down back into CO2 to start the process again
112
Q

What are the two types of photosynthesis?

A

Cyclic and non-cyclic

113
Q

Describe non-cyclic photosynthesis/photophosphorylation

A
  • e- flow in one directional pathway
  • e- flow from the split of H2O into PS || and then through PS | and then to NADPH
  • once in the NADPH (the final acceptor), they can be transported around the cell to generate ATP or another source of energy
  • generates O2, ATP, NADPH
114
Q

Describe cyclic photosynthesis/photophosphorylation

A
  • e- flow in a continuous cycle
  • the source of e- is not from H2O and they flow straight to PS | and ATP is generated
  • no oxygen is produced
115
Q

What are some similarities between cyclic photosynthesis and non-cyclic photosynthesis?

A
  • Both are processes that use light for energy (ATP)
  • Both processes produce NADPH
  • Both processes fix carbon
116
Q

Between cyclic photosynthesis and non-cyclic photosynthesis, which one generates oxygen?

A

Non-cyclic photosynthesis

117
Q

Give an example of how microorganisms exploit their environment (light)

A
  • light is a common resource
  • rather than competing for the light, microorganisms tune their antenna to different wavelengths
    eg.
    The light pigments of algae and cyanobacteria are absorbing light at a narrow wavelength. The other light can pass through to lower layers without being harvested
    Purple bacteria have different pigment (purple chlorophyll) which is tuned to a different wavelength so they can harvest different light to the algae
    The pigment of the bottom microorganism has a wide spectrum so it is mopping up anything that is not being absorbed in the previous layer (not a specialist, a generalist)
118
Q

Give an example of how microorganisms exploit their environment (oxygen)

A
  • bacteria live in anoxic environments
  • they can create cables to shuttle e- from the anoxic zone to the oxic zone
  • this allows them to breathe in oxygen while living in anoxic environments
119
Q

What is the microbiota?

A

Individual microbial species in a biome - bacteria, fungi, archaea and viruses

120
Q

What were the human microbiome goals?

  1. To develop a _______ __________ of microbial genome ________ and to perform ___________ characterisation of the ______ ________
  2. to explore the relationship between _________ and changes in the _______ ________
  3. to develop new __________ and _________ for __________ _____________
  4. to establish a __________ _________
  5. to study the __________, __________ and ________ ___________ of the human microbiome research
A
  1. to develop a reference set of microbial genome sequences and to perform preliminary characterisation of the human microbiome
  2. to explore the relationship between diseases and changes in the human microbiome
  3. to develop new technologies and tools for computational analysis
  4. to establish a resource repository
  5. to study the ethical, legal and social implications of human microbiome research
121
Q

What is the phyla?

A

Types of organisms

122
Q

What is meant by the metabolic pathways?

A

the functions of genes and enzymes in the microbiome

123
Q

It is more important to keep the function than to keep the

A

specific organism

124
Q

Every person had the same collection of

A

enzymes within the same site and only slight variation from site to site

125
Q

What are the 4 bacterial groups?

A
  • firmicutes
  • bacteroidetes
  • actinobacteria
  • proteobacteria
126
Q

Which part of the body has the highest density of microbes in the human body?

A

the gut

127
Q

Where in our gut are there the most microbes?

A

the colon

128
Q

What are functional foods?

A

foods claimed to have a health promoting or disease preventing property beyond the basic function of supplying nutrients

129
Q

What are the probiotics that are often sold, and why?

A

Lactic acid bacteria and bifidobacteria because they can both survive in an acidic environment and so can pass through the stomach into the intestine

130
Q

What is the difference between probiotics and prebiotics?

A

Probiotics are alive and are usually bacteria or yeast whereas prebiotics are an ingredient that beneficially nourishes the good bacteria already in the large intestine to stimulate the growth of probiotics

131
Q

What is a fecal microbiota transplantation used for?

A

to treat Clostridium difficile infections (CDI)

132
Q

How does a fecal matter transplant work?

A
  • shit from a healthy donor is used to replace a patient’s gut microbial flora
  • the shit is blended with saline and put through a stainer and can be frozen before use
  • the shit can be applied to the small intestine:
    1. via a tube through the nose or mouth
    2. deep into the large intestine using a colonoscopy
    3. shoving the shit up your arse to reach the large intestine
133
Q

What are some risks of a FMT?

A
  • diseases
  • complications due to procedures
  • identification of correct donors
134
Q

What are some solutions of a FMT?

A
  • synthetic communities

- stool banks (a collection of donors wit the best microbiome to treat the disease)

135
Q

What are viruses?

A

A cellular microorganisms that cannot survive without a host because they have no metabolic abilities of their own

136
Q

What is meant by viruses having no metabolic activity?

A

They cannot make DNA or proteins and cannot carry out metabolism

137
Q

Viruses are

A

obligate intracellular parasites

138
Q

What are obligate intracellular parasites?

A

parasitic entities that hijack the molecular resources of the host and the host can be any type of cells

139
Q

What is the size range of a virus?

A

10 - 400 nm

140
Q

What is the composition of the virus?

A
  1. genetic material
  2. capsid
  3. (in some cases) an envelope of lipids
141
Q

Describe the genetic material of a virus

A

could be double stranded or single stranded DNA or RNA

142
Q

Describe the capsid of a virus

A

A protein coast that surrounds and protects the genetic material

143
Q

What are capsids made out of?

A

Multiple units of the same protein building block known as capsomers

144
Q

What are capsomers?

A

they are subunits of the capsid arranged in a precise and highly repetitive pattern around the nucleic acid

145
Q

In how many types of symmetry can capsomers be arranged in?

A

3

146
Q

What are the 3 types of symmetry that capsomers can be arranged in?

A

helical
icosahedral
complex

147
Q

Describe a helical capsid

A

the capsomere of the capsid is wound around the RNA or DNA in a helical fashion

148
Q

Describe an icosahedral capsid

A

The capsomere of the capsid is arranged in a 20 face icosahedron where each face is an equilateral triangle

149
Q

Describe a complex capsid

A

The head has icosahedral symmetry and the tail is helical

150
Q

Describe the envelope of lipids

A

it surrounds the protein coat of the cell

151
Q

What is a naked virus?

A

One which does not have an envelope of lipids

152
Q

The genome of viruses could be

A

linear
circular
segmented

153
Q

Briefly explain how viruses affect a cell

A

They find a cell, infect it, replicate its genome using the cells machinery, make more virus and go on and infect more

154
Q

What is a host organism?

A

An organism that a virus infects

155
Q

Give an example of a host organism

A

a human

156
Q

What is a host cell?

A

A cell in which a virus multiplies

157
Q

Give an example of a host cell?

A

the CD4+ T cells

158
Q

What is a bacteriophage?

A

a virus that infects and replicates inside a bacteria

159
Q

Bacteriophages can cause two types of infections. What are they?

A

a lytic infection

a lysogenic infection

160
Q

What is the key difference between a lytic infection and a lysogenic infection?

A

In a lytic infection, the host cell dies whereas in a lysogenic infection, the host cell survives

161
Q

Describe a lytic infection in 7 steps

A
  1. the bacteriophage (BPH) attaches to the host cell
  2. its tail fibre recognises specific receptors on the bacterial cell surface
  3. the BPH injects its DNA into the host cell
  4. the BPH uses the host machinery to transcribe its own DNA which encodes for proteins that degrade the bacterial protein
  5. the virus takes over all the cell’s machinery to replicate its own genome
  6. viral particles are made and the virus is assembled
  7. the bacteria bursts when 100-200 viruses have been formed
162
Q

Describe a lysogenic infection in 6 steps

A
  1. the bacteriophage (BPH) attaches to the host cell
  2. its tail fibre recognises specific receptors on the bacterial cell surface
  3. the BPH injects its DNA into the host cell
  4. the viral DNA gets integrated into the host genome
  5. this lysogen does not replicate the viral DNA
  6. the bacteria doesn’t die but the viral DNA remains in the daughter cells
163
Q

What is prophage?

A

viral DNA that is part of the bacterial chromosome

164
Q

What is a lysogen/lysogenic bacterium?

A

a host bacteria with a prophage

165
Q

What can HIV lead to?

A

Acquired immunodeficiency syndrome (AIDS)

166
Q

What are 6 examples of pathogens?

A
  1. viruses
  2. fungi
  3. prions
  4. protozoa
  5. helminths
  6. bacteria
167
Q

What is the significance of the proteins on the envelope?

A

The proteins are how we can determine what sort of influenza virus it is.
For example, it could be H1N1 or H5N1

168
Q

Why do we need vaccines for influenza every year?

A

Because if the two viral cells infects the host cell from two different areas, they can mix and match RNA and there is a constant recalibration of what proteins are on the envelope

169
Q

Give an example of a pathogenic fungi

A

Trichophyton spp. causing ringworm

170
Q

What are prions?

A

mis-folded proteins

171
Q

How do prions multiply so quickly?

A

Because when they interact with healthy proteins, it causes a chain reaction and copies itself (like a zombie)

172
Q

Give an example of a pathogenic bacteria

A

Bacillus anthracis (causing anthrax)

173
Q

What are Koch’s postulates?

A

Guidelines used to demonstrate that a specific pathogen causes disease symptoms

174
Q

How did Koch determine that a specific pathogen causes disease symptoms?

A

He took a mouse that had died from a disease, took a colony of the pathogen and injected it into more mouse and saw that all the mouse had the same symptoms

175
Q

What are the 4 fine prints of Koch’s postulates?

  • where must the pathogen be present?
  • a sample of the microorganism taken from the diseased host can be grown where?
  • a sample of the culture causes what when injected into a healthy host?
  • the microorganism can be recovered from what?
A
  1. the pathogen must be present in every individual with the disease
  2. a sample of the microorganism taken from the diseased host can be grown in pure culture
  3. a sample of the culture causes the same disease when injected into a healthy host
  4. the microorganism can be recovered from the experimentally infected host
176
Q

What are the 4 key stages of microbial pathogenesis?

A
  1. adherence to host cells
  2. invasion of host tissue
  3. replication within host tissues
  4. disease causing damage to host tissue
177
Q

What are bacterial virulence factors (BVF)?

A

things that the bacteria have that allow it to carry out the 4 stages of microbial pathogenesis

178
Q

What is a BVF that allow bacteria to adhere to host cells?

A

fimbriae

179
Q

What are some BVFs that allow bacteria to invade host tissue?

A

it needs motility so it needs

  • flagella
  • surface proteins such as Internalin- related proteins
180
Q

What are some BVFs that allow bacteria to replicate within host tissue?

A

Bacteria need to food to replicate. They get this from iron in RBC. Therefore they have Soderophores which is a protein which rips iron away from the RBC.
They also have capsules to stop the WBC phagocytosing them

181
Q

What are some BVFs that allow bacteria to cause disease to host tissue?

A

Endotoxins

exotoxins

182
Q

What are endotoxins?

A

Lipopolysaccharides (LPS) that are found on the outer-membrane of Gram-negative bacteria

183
Q

When are endotoxins released?

A

When the bacteria are destroyed (either by antibiotics or WBC)

184
Q

What do endotoxins cause?

A

inflammation

185
Q

What are exotoxins?

A

Potentially deadly toxins produced within living bacteria, and then released into the surrounding medium when the bacteria is still alive

186
Q

What are the three types of exotoxins

A
  1. cytotoxins
  2. neurotoxins
  3. enterotoxins
187
Q

Give an example of a cytotoxin to explain its function

A

Streptolysin which causes the complete lysis of red blood cells

188
Q

Give an example of a neurotoxin to explain its function

A

Botulinium causes paralysis by preventing the release of ACh in the synapse between the axon terminal and the skeletal muscle

189
Q

Which is the most deadly exotoxin?

A

Neurotoxins

190
Q

Give an example of a enterotoxins to explain its function

A

Shiga toxin causes bloody diarrhoea

191
Q

What is meant by the term “selective toxicity”?

A

Drugs (ie. antibiotics) that target the microbial cell but not the host cells

192
Q

What is penicillin?

A

The secondary metabolite excreted by the fungi penicillium which causes a zone of inhibition

193
Q

What is a zone of inhibition?

A

the zone where the bacterial growth is inhibited

194
Q

What are six bacterial cell components which antibiotics target?

A
  1. inhibition of cell wall synthesis
  2. inhibition of protein synthesis
  3. distribution of the cytoplasmic membrane
  4. inhibition of the general metabolic pathway
  5. inhibition of DNA or RNA synthesis
  6. inhibition of pathogen’s attachment or entry into a host cell
195
Q

How can bacteria become resistant to antibiotics?

A

There is diversity within the population of bacteria and if there is a mutation in a bacteria that gives it a survival advantage (eg it is resistant to antibiotics), it will survive and be able to asexually reproduce.
Overtime, all the bacteria in a population will become resistant (natural selection)

196
Q

Why can antibiotics not kill resistant bacteria?

A

Antibiotic resistant bacteria produce an enzyme which destroys penicillin

197
Q

What is the enzyme which destroys penicillin?

A

beta lactamase

198
Q

What two ways can genes be transferred between bacteria?

A

vertical gene transfer

horizontal gene transfer

199
Q

What is vertical gene transfer?

A

Transferring genes from the parent to the offspring

200
Q

What are four ways to reduce the development of antibiotic resistance?

A
  1. decrease antibiotic utilisation
  2. improve diagnostics
  3. identify new targets
  4. combination therapies
201
Q

Explain what is meant by “decrease antibiotic utilisation”

A

Reduce infections and outbreaks through improved hygiene and infrastructure and restrict use in agriculture

202
Q

Explain what is meant by “improve diagnostics”

A

Improve the accuracy of the diagnosis so that people can be accurately treated

203
Q

Explain what is meant by “identify new targets”

A

Make new antibiotics with cellular pathways which are harder for bacteria to bypass

204
Q

Explain what is meant by “combination therapies”

A

give two drugs at once ie. give traditional antibiotics that can be combined with molecules that block resistance mechanisms

205
Q

What are three properties of a bacterial genome?

A
  1. typically a single circular chromosome
  2. there is no nuclear membrane
  3. presence of plasmids
206
Q

Instead of having a nuclear membrane, the bacterial DNA is restricted to a defined region of the bacterial cell known as the _________

A

nucleoid

207
Q

What are plasmids?

A

Small circular self replicating DNA molecules found in the cytosol

208
Q

What is horizontal gene transfer?

A

the transfer of genes directly from one organism to another (not parent to offspring)

209
Q

What are the three strategies of horizontal gene transfer?

A
  1. transmission
  2. conjugation
  3. transduction
210
Q

Describe the process of horizontal gene transfer via transmission

A

When a bacteria dies (killed or naturally) and they spill their chromosomal DNA.
This naked DNA from the dead bacteria enters live bacteria and transforms it

211
Q

Describe the process of horizontal gene transfer via conjugation

A

The sex pilus of one bacteria makes contact with another bacteria and the plasmids can be fed through the sex pilus into the next bacteria

212
Q

What is a sex pilus?

A

A gene transfer tool used by bacteria for conjugation

213
Q

Describe the process of horizontal gene transfer via transduction

A

A bacteriophage injects its DNA into a bacteria and takes over the bacteria
The bacteria DNA breaks up
The viral DNA instructs the bacteria to make more phages.
When they are being put together, instead of using their own DNA, the phages take up bacterial DNA.
When the phages leave the cells and inject DNA into another cell, they inject bacterial DNA

214
Q

Phage virus can turn bacteria into

A

toxin producing bacteria through lysogenic combination

215
Q

Give an example of a bacteria that becomes pathogenic due to lysogenic combination

A

Cholera

216
Q

What is lysogenic transduction?

A

when a bacteria in the lysogenic cycle ejects the viral DNA and the lytic cycle can occur

217
Q

What are the five stages of infectious disease?

A
  1. incubation
  2. the prodromal period
  3. illness
  4. decline
  5. convalescence
218
Q

What happens during the incubation period?

A

The pathogen has invaded the tissue and begins to multiply but there are no signs or symptoms

219
Q

What happens during the prodromal period?

A

The pathogen has reached a certain level so there are vague signs and symptoms

220
Q

What happens during the illness period?

A

There are the most severe signs and symptoms

221
Q

What happens during the decline period?

A

There is a decline in the signs and symptoms and the immune system is working (often with drugs) so kill the pathogens

222
Q

What happens during the convalescence period?

A

There are no signs or symptoms, even though the pathogen could still be there

223
Q

What causes the common cold?

A

A virus called the rhinovirus

224
Q

Describe the rhinovirus:

  • Does it have single or double stranded RNA or DNA?
  • Does it have an envelope?
  • What temperature does it like to grow at?
A
  • ssRNA
  • non-encapsulated (ie. no envelope)
  • grows at 32 degrees
225
Q

The capsid of the rhinovirus has proteins which bind to the

A

respiratory epithelia

226
Q

What is epidemiology?

A

The study of disease transmission

227
Q

What are the six components of the “chain of infection”?

A
  1. causative agent
  2. reservoir/source
  3. means of exit; way out of the body
  4. mode of transmission/method of spread
  5. portal of entry/way into the body
  6. person at risk
228
Q

What are the possible causative agents according to the “chain of infection”?

A

virus
bacteria
parasite

229
Q

What are the possible reservoir/sources according to the “chain of infection”?

A 
human
animal
fomite
food
water
230
Q

What are the possible modes of means of exit; ways out of the body according to the “chain of infection”?

A

excretions
secretions
droplets

231
Q

What are the possible modes of transmission/methods of spread according to the “chain of infection”?

A

contact
airborne
vector

232
Q

What are the possible portal of entry/ways into the body according to the “chain of infection”?

A

Respiratory
Gastrointestinal system
Mucous
Skin

233
Q

Who are the people at risk according to the “chain of infection”?

A

Young
Immunocompromised
Elderly

234
Q

What are some ways to break the chain of infection in terms of the causative agent?

A

Rapid detection and treatment

235
Q

What are some ways to break the chain of infection in terms of the reservoir/source?

A

good hygiene
sterilisation
disinfectant

236
Q

What are some ways to break the chain of infection in terms of the means of exit; way out of the body?

A

waste removal

disinfectant

237
Q

What are some ways to break the chain of infection in terms of the mode of transmission/method of spread?

A

airflow control

bed spacing

238
Q

What are some ways to break the chain of infection in terms of the mode of the portal of entry/way into the body?

A 
Aseptic technique (keeping things clean)
Wound care
239
Q

What are some ways to break the chain of infection in terms of the mode of the people at risk?

A

Identifying those at risk and targeting them for special care, vaccination and education

240
Q

Define mortality

A

the occurrence of death in a population

241
Q

Define morbidity

A

the occurrence of a disease, including fatal and non-fatal diseases

242
Q

Define incidence

A

the number of new cases of the disease at a given time

243
Q

define prevalence

A

the total new and existing cases in a population at a given time

244
Q

Define endemic

A

the amount of that particular disease that is usually present in a community

245
Q

Define sporadic

A

a disease that occurs infrequently and irregularly

246
Q

Define epidemic

A

a sudden increase in the number cases of a disease above what is normally expected in that area

247
Q

Define pandemic

A

an epidemic that has spread over several countries or continents, usually affecting a large number of people

248
Q

Outline the selective pressures that HIV is under

A

Selective pressures:

  1. the immune system and changes in the receptor: viruses with the ability to bind to the CD4 receptors can survive
  2. drugs: viruses with mutations that stop drugs from killing them can survive
  3. the tissues: some viruses have variants that will allow the viruses to survive better in some tissue than others
249
Q

Explain how patterns of relationships between sequences might provide evidence for evolution

A

HIV viruses within a patient are more similar than between patients. This, along with the pattern of the phylogenetic tree suggests a single point of entry and then diversification.
We also have all the requirements for natural selection:
1. variation
2. inheritance
3. selection
4. time

250
Q

Explain how the HIV virus accumulates a lot of variation:

A

The reverse transcriptase is very error prone when turning RNA into DNA which means that there are many mutations and therefore variants formed even within one individual

251
Q

Explain how the HIV virus is inherited

A

The HIV virus passes on their RNA after being inserted into the genome

252
Q

Explain how the HIV virus can accumulate variations over. a number of generations

A

The HIV lifecycle is very fast (20 mins) so there is plenty of time to accumulate many variations

253
Q

Outline the role of evolutionary change in the virulence of pathogens

A

HIV evolves so quickly that there could be up to 5 x 10^10 different variants of the virus in one individual. This means that it is very hard to make effective vaccines very hard.

254
Q

Describe the importance of evolutionary thought to our understanding of disease

A

evolution is a key way that pathogens respond to hosts and therapy so understanding evolution can help us respond better to pathogens

255
Q

Explain that by comparing DNA sequences, we can help understand their relationship

A

By sequencing DNA of HIV, we can see what is different and we can use this to see how there can be variation in patients and between patients.

CELS 191 (5 decks)

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