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Microbiology > Week 1 > Flashcards

Week 1 Flashcards

1
Q

When did microbial cells evolve?

A

Around 3.5 bya

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2
Q

Who suggested the existence of microorganisms?

A

Lucretious (98-55BC) and Fracastoro (1478-1553)

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3
Q

What did Stelluti (1625-1630) do?

A

Used microscope to see microorganism

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4
Q

Who published drawing of microorganism?

A

Hooke (1655)

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5
Q

What did Antony Van Leeuwenhoek (1670’s) do?

A

Used microscope inspired by lens from fabric inspection to observe and draw bacteria from dental plaque

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6
Q

What cell theory was believed in until 18th century?

A

The pre-cell theory of spontaneous generation from non-living matter.

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7
Q

Who proved spontaneous generation theory wrong and how?

A

Louis Pasteur (1822-1895) filtered air through cotton wool and found spore-like things in it which grew when placed in sterile medium. Then he conducted an experiment called Pasteur’s Flask (1861).

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8
Q

What else did Pasteur do?

A

Experimented with wine and laid the basis of germ theory of disease.

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9
Q

What two other theories were there early on?

A
  • Miasmas (poisonous vapours)

- Imbalance of the 4 humors (blood, phlegm, yellow bile and black bile).

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10
Q

What did Ignaz Semmelweiss do?

A

Noted more deaths when physicians delivered babies then midwives.

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11
Q

Who noted drinking certain sources of water caused cholera?

A

John Snow (1849)

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12
Q

What did Joseph Lister (1867) do?

A

Used heat and phenol to reduce surgical infections.

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13
Q

What did Robert Koch (1843-1910) discover?

A
  • Showed specific organism caused specific disease (bacillus anthracis caused anthrax)
  • Developed agar and petri dishes, methods of sterilisation, disinfection and filtration
  • Discovered causative agent of tuberculosis and other diseases.
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14
Q

Who and when verified the germ theory of disease?

A

Robert Koch in 1876.

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15
Q

What were some limitations of Koch’s original postulates?

A
  • Some pathogens are part of normal microbiota
  • cannot always be grown
  • some grow/cause disease only in humans
  • more than one pathogen may be involved
  • variety in immune status
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16
Q

List Koch’s original postulates.

A
  1. The microorganism must be present in every case of the disease but absent from healthy organism.
  2. The suspected microorganisms must be isolated and grown in pure culture.
  3. The same disease must result when the isolated microorganism is inoculated into healthy host.
  4. The same microorganisms must be isolated again from the diseased host.
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17
Q

What was different in Koch’s molecular postulates?

A
  • Emphasised virulence genes (VG) rather then microorganism itself.
    Stated that:
  • VG must be found in pathogenic strains of microbes
  • VG must be expressed during infection/disease
  • Mutation (or deletion) of VG decreases pathogenicity
  • Replacement/restoration of VG mutation/deletion restores pathogenicity
18
Q

What is virulence gene?

A

Genes within microbes that encodes characteristic allowing microbes to cause disease.

19
Q

What is the current microbial taxonomy?

A
  • Based on phylogenetic system comparing organisms on the basis of evolutionary relationships.
  • compared using small subunit (SSU) rRNA nucleotide sequences between microbes (16S and 18S).
20
Q

What is a species?

A

Strains that share stable properties and differ significantly from other strains.

21
Q

What is a strain?

A

Genetically identical and grown from one parent.

22
Q

What is a pure culture?

A

Genetically identical because they arise from single cell.

23
Q

What are some similarities between archaea and bacteria?

A

Cell shapes and size (cocci and rods)

24
Q

What are some differences between archaea and bacteria?

A
  • Cell wall composition (archaea made of glycoprotein/protein/polysaccharide not peptidoglycan)
  • Archaea’s membrane lipids are ether-linked (more stable)
25
Q

What ribosomes do bacteria have?

A

70S

26
Q

What arrangements can bacteria be found in?

A

Chains (streptococcus agalactiae), clusters (staphylococcus aureus) or both

27
Q

What structures make up the bacterial cell envelope?

A
  • Plasma membrane
  • Cell wall
  • SOME have optional extracellular layer
28
Q

What do bacteria have instead of cholesterol in its PM?

A

Hopanoids

29
Q

What is the role of a bacterial cell wall?

A
  • Determine shape and assist cell strength due to peptidoglycan
  • Protects against osmotic lysis and toxins
  • Some components may contribute to pathogenicity such as LPS in gram- bacteria.
  • Site for several antibiotics
30
Q

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

A
  • Higher number of X-linking in PG= gram+
  • Lower number of X-linking in PG= gram- (more porous/thinner PG layer)
  • Gram+: no outer membrane, thicker PG layer, periplasmic space is smaller
  • Gram-: has outer membrane, larger periplasmic space
31
Q

Describe a capsule.

A
  • organised polysaccharide, not easily washed off
  • aids in cell adhesion, pathogenesis
  • protects against dehydration, phagocytosis, bacteriophage
  • visualised by negative staining (mounted in India ink)
32
Q

Describe slime layer.

A
  • unorganised polysaccharides, easily washed off

- not easily visualised

33
Q

What is an S-layer?

A
  • arrays of protein or glycoprotein
  • Found in many GP, GN and the archaea
  • Aid in cell shape and rigidity, adhesion, pathogenesis
34
Q

What are inclusions?

A
  • Common in all cells
  • Aggregates of organic or inorganic material (free-floating in cytoplasm or surrounded by single-layered membrane)
  • Mainly used for storage
35
Q

What is included in the bacterial genome?

A

Nucleoid and plasmids

36
Q

What triggers sporulation?

A

When growth ceases, can be due to environmental stress (lack of nutrients)

37
Q

What three components make up the flagella?

A
  • Filament: composed of helical array of flagellin
  • Hook: gives ability to turn, rotate and spin
  • Basal body: located within cell envelope layers
38
Q

Describe structure and function of pili.

A
  • Short, hair-like appendages composed of helicalled arranged pilin.
  • Functions include attachment to surfaces, type IV assist in motility and uptake of DNA from external environment, sex pili transfer plasmids (conjugation)
39
Q

What are the 3 types of ‘bacterial motility’?

A
  • Flagellar motility (only true bacterial motility)
  • Twitching motility: short intermittent jerks
  • Glidong motility: smooth motility
40
Q

What is chemotaxis?

A
  • Moving in a series of runs (straight) and/or tumbles.

- Can be along concentration gradient towards nutrients or down a concentration gradient away from wastes/toxins.

41
Q

What is growth rate?

A

Number of generations per unit time

42
Q

What phases are part of the bacterial growth curve?

A
  • Lag phase: Cells are metabolically active but not increasing in number.
  • Exponential phase: Adaptation is complete
  • Stationary phase: Total number of living (viable) cells remain constant.
  • Death phase: Conditions are less supportive of cell division.

Microbiology (8 decks)

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