MIIM - Introduction to Infectious Agents - Week 1 Flashcards

1
Q

How have microorganisms imapcted the world in the past? Describe what this process is known as, and why it is so important.

A

They allowed the process of nitrogen fixation into the soil. These bacteria can be found on the roots of some pants, such as legumes, and allow them to incorporate nitrogen. Herbivores eat these plants, who are then eaten by carnivores, or die naturally. As they decay, their nitrogen content is once again recycled into the soil, air, or water. This is the nitrogen cycle.

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2
Q

Describe nitrogen fixation.

A

When nitrogen in the air is is fixated into the soil by bacteria.

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3
Q

Describe ammonification.

A

When decaying organic compunds have their nitrogen content converted to ammonia by decomposers.

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4
Q

Describe nitrification.

A

The process by which ammonia in the soil is converted to nitrites and nitrates by nitrifying bacteria.

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5
Q

Describe denitrification.

A

When nitrates are converted to nitrogen gas by denitrifying bacteria.

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6
Q

Describe assimilation.

A

When nitrates are taken up by plant organisms.

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7
Q

Where do bacteria sit on the food chain, and how do they support it?

A

They sit at the bottom, and support the entire chain by providing essential nutrients.

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8
Q

How do bacteria support humans?

A

In the gut, by synthesising essential B vitamins such as thiamine (B1), riboflavin (B2), pantothenic acid (B5), biotin (B7), and folate (B9).

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9
Q

Are the majority of microbes good/neutral, or harmful?

A

Good/neutral. Only a handful are associated with infectious disease.

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10
Q

Name the 5 types of infectious agents. Note which are acellular.

A

Bacteria, fungi, parasites, viruses, and prions.
Viruses and prions are acellular.

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11
Q

What is characteristic of prokaryotic organelles vs eukaryotes?

A

They are free-floating in prokaryotes, and are not membrane-bound, as in eukaryotes.

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12
Q

Compare prokaryotic DNA with eukaryotic DNA (2).

A

Prokaryotic DNA is closed and circular.
Eukaryotic DNA is linear.

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13
Q

What ribosome density unit do prkaryotes and eukaryotes have?

A

Prokaryotes use 70S
Eukaryotes use 80S

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14
Q

How do prokaryotes and eukaryotes replicate?

A

Eukaryotes - mitosis/meiosis
Prokaryotes - binary fission

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15
Q

Which of the following are present in prokaryotes?
Endoplasmic reticulum
Peptidoglycan
Plasma membrane sterols

A

None except peptidoglycans.

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16
Q

Describe what is meant by site-specific pathogenicity.

A

Occurs when bacteria appear neutral or beneficial in one location, but when moved to another region, they are pathogenic.

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17
Q

Name 6 factors that can affect a microbiome composition.

A

Climate/geography
Age
Shared living (family/aged care)
Personal hygiene
Diet
Medical treatment/intervention/hospitalisation

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18
Q

What is the periplasmic space?

A

The space between the cell wall and the inner cell plasma membrane.

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19
Q

What confers shape to a bacteria?

A

Cell wall

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20
Q

What term is given to rod-shaped, spherical, and spiral forms of bacteria?

A

Rods - bacilli
Spherical - cocci
Spiral - spirilla

21
Q

Do all bacteria have cell walls?

A

No, such as mycoplasma

22
Q

Describe the cell wall layers of gram-positive (3), gram-negative (2), and acid fast bacteria (5).

A

Gram negative have:
Inner plasma membrane
Thinner peptidoglycan layer
Outer membrane

Gram positive have:
Inner plasma membrane
Thicker peptidoglycan layer

Acid fast have:
Outer lipid layer
Thick mycolic acid layer
Arabinogalactan layer
Thin peptidoglycan layer
Inner plasma membrane

23
Q

What is peptidoglycan also known as, and what 2 subunits are used to form bacterial cell walls?

A

Murein.
Subunits are N-acetyl muramic acid, and N-acetyl glucosamine.

24
Q

What structure joins chains of peptidoglycan in bacterial cell walls?

A

A chain of amino acids extending downwards (L-Ala, D-Glu, L-Lys, D-Ala), connected by a penta-glycine bridge (connecting one D-Ala to another L-Lys).

25
Q

What component of the immune system recognises bacterial cell wall components?

A

Toll-like receptor 2 TLR2

26
Q

Describe the procedure for a gram stain, and what happens to the bacteria in each step.

A

-A bacterial emulsion is placed on a slide, and allowed to air-dry if neccessary.
-The slide is heatfixed using a flame to fix and kill the bacteria.
-Crystal violet is applied. It stains everything purple.
Iiodine is added as a mordant, and complexes with the crystal violet to prevent it from being removed in the next step.
-Acetone/alcohol is used as a decolouriser to remove crystal violet.
-Dilute carbol fuchsin is used as a counterstain to stain everything pink.
-The slide is washed a final time with water and allowed to air-dry.

27
Q

Describe how gram-positive and negative bacteria stain with a gram stain, and why this is the case.

A

Positive - purple
Negative - pink
Iodine binds with crystal violet to prevent it from exiting a bacterial cell. This only applies to gram-positive bacteria due to their large peptidoglycan layer.
Gram-negative bacteria have a thinner peptidoglycan layer, and thus the crystal violet is removed with the decolouriser, and counterstained with catbol fuchsin.

28
Q

Describe a benefit of gram-positive bacteria having a thick peptidoglycan layer.

A

Resistance to drying and disinfectants.

29
Q

Describe a benefit of gram-positive bacteria having a thinner peptidoglycan layer and outer membrane.

A

The periplasmic space is the site for many specialised proteins, and the outer membrane allows resistance to antibiotics.

30
Q

What are plasmids?

A

Circular DNA that form extra genes and are transferrable.

31
Q

What are flagella?

A

Confers motility by rotating.

32
Q

What are pilli and fimbriae?

A

Pili allows conjugation
Fimbriae allows adhesion

33
Q

What is a bacterial capsule, what is it composed of, what does it aid in, and how does it affect recognition by the immune system?

A

Usually is a secretion of polysaccharides.
It can aid in adhesion, and masks immunogenic structures, evading the immune system.

34
Q

Describe a bioflim.

A

Biofilms result when capsule secretions are less structured, and can result in a slime or biofilm layer.
They are large hydrogel ECM in which bacteria replicate and signal to one another.

35
Q

How do bacteria signal within a biofilm?

A

Quorum sensing

36
Q

Describe endospores.

A

When environmental conditions become difficult, all the essential components of the bacteria such as the DNA and ribosomes are packaged into an endospore. The rest of the cell bursts open and releases the endospore, which is extremely resistant to sterilisation and heat.

37
Q

Name the 3 types of bacteria by their metabolism. Describe why they are so.

A

Obligate anaerobes - cannot tolerate oxygen gas. The end-products of aerobic metabolism is toxic to them, such as hydrogen peroxides and superoxides. They lack the enzymes to deal with these.

Aerotolerant anaerobes - can tolerate, but do not use oxygen gas, as they have the appropriate enzymes to deal with the peroxide/superoxides.

Facultative anaerobes - can grow aerobically or anaerobically.

38
Q

Describe the 4 phases of bacterial growth as seen in a lab.

A

Lag phase - flat line at the beginning in which the bacteria are preparing to grow in their medium. Their numbers are doubling every cycle.
Logarithmic phase - as bacterial numbers double per cycle, their numbers grow rapidly, and on a log-curve, this appears as a linear line.
Plateau - bacterial numbers slow and eventually plateau due to the low availability of nutrients or space.
Decline - bacterial numbers begin to decrease due to depleted nutrients, space, or accumulation of toxic metabolic end-products.

39
Q

Describe briefly how a MALDI-TOF can be used as an automated identification system for bacteria.

A

A series of 96 wells are placed underneath a mass-spectrometer. Each well is sequentially ionised, which is then read by the spectrometer.
Each species of bacteria will have its unique pattern on the readout, which can be compared to a central database for quick identification.
Building this central database in the first place will require manual purification of bacterial colonies in order to obtain individual unique patterns.

40
Q

Are viruses considered living?

A

No

41
Q

What kind of genetic material can viruses contain (4)?

A

dd or ss DNA/RNA

42
Q

Are viral nucleic acids linear or circular?

A

Can be linear or circular.

43
Q

Do viruses always have a capsid or envelope?

A

Not always, they can be a naked piece of nucleic acid

44
Q

What can persistent viral infections cause?

A

Cancer

45
Q

Whar do enveloped viruses do to tner a membrane?

A

They first fuse with the target membrane.
Once theyve replicated, new viruses bud off the infected cell.

46
Q

Do fungi reproduce sexually or asexually?

A

Both

47
Q

What are fungal infections typically associated with?

A

Contact lens wear.

48
Q

How can prion diseases spread in an ophthalmic context?

A

Very rarely through conreal transplant