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Microbiology > Prokaryotes > Flashcards

Prokaryotes Flashcards

1
Q

LO

A

Understand major theories on the origin of life
Appreciate the diversity of prokaryotic life
With reference to bacteria
With reference to archaea
Describe the key differences between bacteria and archaea

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2
Q

morphology

Selective forces may be involved in setting the morphology

A
  1. Optimization for nutrient uptake
  2. Swimming motility in viscous environments or near surfaces e.g. spiral-shaped cells
  3. Gliding motility e.g. filamentous bacteria
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3
Q

importance of cell size scaling

A

Surface area to volume ratio key for diffusion across membranes and within cytosol

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4
Q

Cell wall

2 points

A

rigid layer present outside the cytoplasmic membrane

confers structural strength on the cell and protection from osmotic lysis.

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5
Q

cell wall properties

4 points

A
  1. Relatively permeable and most microorganisms have one.
  2. Stronger than the membrane, give shape and rigidity to the cell.
  3. Prevents lysis due to osmotic pressure.
  4. Main discriminatory character between different groups of bacteria.
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6
Q

S-layer

3 points

A
  1. Crystalline cell-surface layer on some bacteria and most archaea
2. Comprised of glycoproteins
Protects the cell from the environment:
Bacteriophage
Low pH 
Lytic enzymes
Predatory bacteria
  1. Additional functions:
    Surface adhesion
    Biomineralisation
    Membrane stabilisation
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7
Q

bacteria colonies

A

bacteria grow on solid media as a distinct colony originating from a single mother cell;
therefore, all cells in a colony are ‘clones’

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8
Q

Descriptive characteristics of a colony:

A

Form
Elevation
Margin
Colour (substrate/aerial)

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9
Q

see desktop for colony / bacteria morphology

A

.

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10
Q

Motility

2 points

A
  1. Microbial locomotion is a differential characteristic within bacteria.
  2. Movement allows cells to reach different parts of their environment under their own power.
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11
Q

motility 2 main mechanisms

A

Flagella

Gliding motility

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12
Q

Flagellum/Flagella

3 points

A
  1. The flagellum is a thin, whip-like, motility structure in bacteria.
  2. Rotor driven by proton-motive force, or sodium gradient
    Unloaded speed up to 17,000 rpm, with flagellum up to 1000 rpm.
  3. Direction/speed can be changed in response to environmental conditions.
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13
Q

Gliding

4 points

A
  1. Movement across solid surfaces of some bacteria that lack flagella.
  2. Slower and smoother than flagellar motility
  3. Movement occurs along the long axis of the cell.
  4. Types:
    polysaccharide production
    twitching motility: type IV pili
    movement of cell’s proteins
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14
Q

Sporulation

3 points

A
  1. A dormant, tough, and temporarily non-reproductive structure produced by certain bacteria in response to adverse changes in the environment
  2. One spore can survive for thousands of years.
  3. Major medical issue:
    Closdridioides difficile
    Bacillus anthracis
    Clostridium botulinum
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15
Q

sporulation cycle (see picture on desktop)

A

.

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16
Q

Spore formation and morphology (see picture on desktop)

A

.

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17
Q

Reproduction
Asexual reproduction by
3 points

A

Binary fission
Budding
Fragmentation

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18
Q

Reproduction
Conjugation
2 points

A
  1. Most bacteria can conjugate
  2. Conjugation occurs via pili: there is a donor cell containing a conjugative plasmid and a recipient cell which does not. Only donor cells have pili.
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19
Q

Reproduction
Tranformation
3 points

A
  1. Uptake of ’naked’ extracellular DNA
  2. Induced by environmental stresses
  3. DNA uptake via competence pili
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20
Q

Reproduction

Transduction

A
  1. Transfer of DNA via bacteriophage infection
21
Q

Metabolism see desktop for diagram

A

.

22
Q

Compartmentalisation
(organelle-like structures)

Storage of carbon/ nitrogen/ phosphorus

3 points

A
  1. PHB, starch granules
  2. Polyphosphate
  3. Nitrate
23
Q

Compartmentalisation
(organelle-like structures)

Protection of the cell from toxic intermediates of metabolic pathways

3 points

A
  1. Encapsulin nanocages
  2. Ferritins
  3. Bacterial microcompartments
24
Q

Compartmentalisation
(organelle-like structures)

Enhancement of speed/efficiency of metabolic pathways

2 points

A
  1. Carboxysomes

2. Lumazine synthase

25
Q

Traditional bacterial classification

A

‘artificial’ based on arbitrary morphological and biochemical characteristics.

26
Q

recent molecular and structural work has revealed

A

as much diversity within Bacteria as within all eukaryotes.

27
Q

Molecular phylogenetics now reveals

A

underlying phylogenetic relationships between bacteria.

28
Q

Archaea the microorganisms of

A

the extreme environments

but they are present in much more common habitats too

29
Q

Archaea
Cell Morphology
6 points

A
  1. Coccus
  2. Bacillus
  3. Filamentous bacteria
  4. Triangular
  5. Square
  6. Irregular shaped
30
Q

Archaea

size

A
  1. most <1um
31
Q

Archaea
cell wall
3 points

A
  1. No peptidoglycan
  2. Typically no outer membrane
  3. s-layers, psuedomurein or other polysaccharides
32
Q

Archaea

cell wall - s layers

A
  1. Most common cell wall type among Archaea
  2. Formed by proteins or glycoproteins
  3. Paracrystalline structure
33
Q

Archaea

psuedomurein

A
  1. Found in cell walls of certain methanogenic Archaea
  2. Polysaccharide similar to peptidoglycan
  3. Composed of
    N-acetylglucosamine and
    N-acetylalosaminuronic acid
34
Q

Archaea
Colony morphology
2 points

A
  1. no difference in colony morphology between Bacteria and Archaea.
  2. At first all Archaea were considered Bacteria.
35
Q

Archaea
Motility
5 points

A
  1. The Archaellum: Archaeal flagella
  2. Thinner than bacterial flagella
  3. Make a rotation (but their motor is still unknown)
  4. Different composition (including some glycoproteins)
  5. Probably slower due to its size
36
Q

Archaea

Sporulation

A

No known archaeal species sporulates!

37
Q

Archaea

reproduction

A

similar to bacteria

38
Q

Archaea, rather than being the most primitive bacteria are a

A

highly diverse group of highly evolved prokaryotes

the sister clade to all Eukaryotes.

39
Q

Archaea

They are present in

A

many different habitats (and play key roles in extreme environments.)

40
Q

Ancestral eukaryote probably arose from

A

endosymbiosis of a bacterium within an archaeal cell!

41
Q

Main differences between bacteria and archaea
5 points bacteria
6 points archaea

A

Bacteria

  1. Peptidoglycan in cell wall
  2. Movement by gliding
  3. No histones
  4. Only one RNA polymerase
  5. Inhibited by streptomycin and chloramphenicol antibiotics

Archaea

  1. Psedopeptidoglycan in cell wall
  2. Can grow over 100 ºC
  3. Histones associated with DNA
  4. Several types of RNA polymerase
  5. Not inhibited by streptomycin and chloramphenicol antibiotics
  6. More eukaryotic-like proteins – additional organisation of cytosol
42
Q

similarities between bacteria and archaea

6 points

A
  1. Prokaryotic cells
  2. Circular chromosomes
  3. Lack nuclear envelopes
  4. No membrane-enclosed organelles
  5. Possess cell wall
  6. Presence of flagella
43
Q

the name given to the last universal common ancestor.

A

LUCA

44
Q

Classification of microorganism has changed through the time thanks to

A

newly developed technologies.

45
Q

Diversity among Bacteria and Archaea is

A

really high.

Some differences could be observed in morphology, size, structure, motility and resistance forms.

46
Q

Archaea have been studying as an independent domain for fewer years =

A

some of their systems are still less understood than in Bacteria.

47
Q

origin of life

A

look up miller urey experiment

look up panspermia

48
Q

bacterial morphology 1

A

desktop

Microbiology (13 decks)

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