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LSCI 230 > Structure and function of prokaryotes > Flashcards

Structure and function of prokaryotes Flashcards

1
Q

Name the 6 Shapes of Bacteria and Archaea

A 
coccus
rod
spirilles
spirochete
stalk/hypha
filamentous bacteria
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2
Q

What does the shape depend on?

A

mostly on the cell wall

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3
Q

Function of the cells wall (2)

A

the cell wall allows bacteria to withstand the intracellular osmotic pressure (about the same as a car tire!) and is responsible for the shape and rigidity of the bacteria.

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4
Q

Name the 2 group of bacteria and according to what are they classified?

A

Gram + and Gram -

depends on their Gram stain

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5
Q

Why do bacteria stain differently?

A

Bacteria stain differently because they have different kinds of cell walls

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6
Q

Describe the 4 steps to do a gram stain

A
  1. flood the heat-fixed smear with crystal violet for 1 min=>all cells are purple
  2. add iodine solution for 1 min=>all cells remain purple
  3. decolorization with alcohol briefly-about 20 sec=> gram +cells are purple, gram - cells are colourless
  4. counterstain with safranin for 1-2 min=> gram + cells are purple, gram - cells are pink/red
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7
Q

give an example of gram +

A

+ staphylococcus aureus

- E coli

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8
Q

explain the difference in the cell wall structure of a bacteria gram + and gram -

A

+: thick peptidoglycan, cytoplasmic membrane, protein

-: outer membrane, thin peptidoglycan, protein

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9
Q

what is a peptidoglycan?

how many variants are there?

A

Peptidoglycan is a polymer (murein). There are many variants of peptidoglycan (>100).

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10
Q

Subunit of peptidoglycan?
What are they
Can you find them in Archaea or Eukarya?

A

• 2 sugars: NAG and NAM
• Short peptide side chain containing unusual amino acids: D‐amino acids, instead of the L‐amino acids found in proteins.
• NAM and DAP (diaminopimelic acid) have never been found in Archaea or Eukarya.
- have l-alanine and d alanine, d-glutamic acid (a peptide)

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11
Q

Polymerization of the sugar backbone:

A

NAG‐NAM‐NAG‐NAM…

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12
Q

what is the target of lysozyme?

where is lysozyme secrete and why?

A

The link between NAM and NAG (beta 1-4) is the target of lysozyme. Lysozyme is secreted in tears, saliva and other body fluids to protect against bacterial pathogens.

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13
Q

why does the sugar backbone polymerize?

A

The polymerisation of the sugar backbone provides rigidity to the structure in only one direction.
GMG—-GMG

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14
Q

how is rigidity provided in the other direction?

A

Anotherbond,between the peptides of two adjacent peptidoglycan chains, provides rigidity in the other direction
• Gram‐negative: direct cross‐linking. DAP—D-Ala
• Gram‐positive: interbridge cross‐linking. L-Lys——Gly

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15
Q

Cross‐linking is called

A

transpeptidation.

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16
Q

Cell wall of Gram‐positive bacteria

1) how much of it is made of peptidoglycan?
2) what is covalently bounded to the peptidoglycan?
3) how are they covalently bound?

A
  • Upto90%ofthewallispeptidoglycan.
  • TA/LTAcomposedofglycerol‐P(3C)orribitol‐ P (5C), and decorated with amino acids and sugars. They are covalently bonded to the peptidoglycan.
  • Wall‐associatedproteinsareattached covalently to the peptidoglycan by an enzyme called sortase.
  • TA: teichoic acid
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17
Q

what is lipoteichoic acid made of ?

A 
DAG (diacylglycerol)
glycerol
long, non polar, hydrophobic fatty acid chains
C=O bonds =>ester linkage
phosphate=>2carbons etc
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18
Q

Cell wall of Gram‐negative bacteria

1) how are the surface proteins anchored to the outer membrane?
2) how much of it is made of peptidoglycan?
3) what is the protein gel + function
4) other name for the outer membrane + function

A

1) hydrophobic domain
2) Peptidoglycan: 5‐10% of the cell wall.
3) The periplasm contains a high concentration of proteins involved in, ex, nutrient acquisition, extracellular enzymatic reactions, sensing, etc. It is so dense that it is sometimes called a “protein gel”.
4) The outer membrane sometimes called LPS layer. The LPS layer helps protect the bacteria against a variety of substances, including antibiotics, and against the host defense system.

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19
Q

what is LPS

A

LPS is a family of complex sugar polymers attached to a lipid moiety known as lipid A.

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20
Q

What is Lipid A+function?
Who should avoid it?
Whats its structure?

A

Lipid A is an endotoxin and it plays a major role in the pathogenesis of Gram‐negative bacterial pathogens.

Lipid A is toxic to many animals, it can cause acute inflammation and vascular problems (septic shock) that can result in death.

Lipid A contains 6 lipid tails that are embedded in the membrane. KDO: 2‐keto‐deoxyoctonate, links the lipid A to the polysaccharide chain. GlcN: N‐acetylglucosamine (as in peptidoglycan)

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21
Q

what areO‐specific polysaccharide+function?

A

O‐specific polysaccharide, also known as the O antigen, consists of repeating sequences of 2‐4 monosaccharides. There are a huge diversity of O antigens so it can be used to identify different strains of one species of bacteria: ex: E. coli O157:H7 (O157 serogroup).

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22
Q

Archaea vs Bacteria structure (2)

A

Peptidoglycanisabsentinthecell wall of Archaea and there is usually no outer‐membrane

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23
Q

What is the Archaea cell wall essentially made of?

A

Cell walls of Archaea are diverse and may consist of proteins (usually), polysaccharides, and/or glycoproteins.

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24
Q

what is pseudopeptidoglycan?

A

The structure of pseudomurein (pseudopeptidoglycan) is similar to peptidoglycan. It contains N‐ acetyltalosaminuronic acid instead of NAM and lacks D‐amino acids.

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25
Q

Whats the link beteween the sugars called and what differentiates them from the one in peptidoglicans?

A

B(1-3)

The linkage between the sugars is insensitive to lysozyme, unlike peptidoglycan.

26
Q

species of Archaea have cell walls composed of repeating units of two or more sugars are called:

A

heteropolysaccharides

27
Q

what is the general appearance of an archaea?

A

These cell walls have a crystalline appearance when viewed by electron microscopy and are referred to as paracrystalline surface layers or S‐layers.

28
Q

Where an S-layers be found?

What does this change?

A

archaea and
S‐layer may also be found in some species of bacteria. In this case the S‐layer forms an additional layer on top of peptidoglycan (Gram‐positive) or on top of the outer membrane (Gram‐negative).

29
Q

Appart from the S-layer, what can bacteria and archaea species also synthesize?

A

Bacterial and archaeal species may synthesize another layer known as the capsule or slime layer depending on its consistency.

30
Q

Function of capsule

A

The capsule is a very important virulence determinant for capsulated bacterial pathogens – the capsule protects against the host defense system.

BUT The capsule or slime layer does not confer significant strength to the cell.

31
Q

Is the capsule made of hetero or homo polysaccharides?

A

Composed of polysaccharides (vast majority) or proteins.
• Heteropolysaccharides (Majority of bacteria)
• Homopolysaccharides (Some Gram‐ negative)

32
Q

What other surface appendages apartment from capsule and S layer? and What are there functions?

A

• In addition, bacteria and archaea may have other surface appendages: flagella and fimbriae.
• Flagella are used for locomotion (motility). Usually 15‐20 μm long. The flagella of Archaea are still not fully understood.
Fimbriae are involved primarily in the attachment of the microorganism to surfaces. They form rigid, rod‐like structures. Usually ≤ 4 μm long. Found primarily on Gram‐negative bacteria.

33
Q

max speed of flagellum like cells

A

Max speed: 50 cell lengths/sec

34
Q

3 types of flagella

A

Peritrichous (many flagella, all around the cell surface)

Lophotrichous (many flagella, originating from one end of the cells, polar flagellation)
Brock Biology of Microorganisms, 13th Edition. 15

35
Q 
what is the flagellin?
# of subunits of flagellin/ flagella?
A

one protein

20,000

36
Q

Flagellum structure

A 
Gram‐negative: L, P, MS and C rings.
  • Gram‐positive: P, MS and C rings
• L–LPS
• P – Peptidoglycan
• MS – Membrane Superficial
• C ‐ Cytoplasm
37
Q

where is the flagellum anchored?

vs flagella/cilia in eukaryotes?

A

cytoplasmic membrane

not covered by the cytoplasmic membrane, much much smaller

38
Q

proton motive force is actioned by what? (motility)

A 
Mot protein
c ring
ms ring
rod
proton gradient
39
Q

steps to synthesis of filament (motility)

A

MS/C ring=>Mot protein=>P ring=>L ring=> early hook=> cap or late hook=> hook filament junction and filament and filament synthesis begins

40
Q 
what does motility require?
# of genes involved in motility and what are they involved in?
A

Motility is very energy intensive. Requires lots of resources.
Over 50 genes involved in motility: biosynthesis of flagella, structure or regulation.

41
Q

where does growth of the filament take place at (motility) ?

A

Growth of the filament take place at the tip; the subunits use the central channel to go from the cytoplasm to the tip.

42
Q

Function of cap in motility?

A

Cap assist flagellins to organize at the Tip.

43
Q

which of the 3 movements are polar?

A

monotrichous and locophotrichous

44
Q

*movement of polar and peritrichous flagella schema to know

A

page 10 of 17

45
Q

Ways to move around in bacteria and archaea?

A

flagella and gliding motility (secretion of mucus, glide proteins, pilus retraction)

46
Q

Taxis? give 4 examples

A

Directed movement toward or away from a gradient of chemical or physical agents.
• Chemotaxis: chemicals, nutrients, antibiotics, etc.
• Phototaxis: light (phototrophic organisms)
• Aerotaxis: oxygen
• Osmotaxis: ionic strength (high/low salt concentration) • Etc.

47
Q

What is the best study of frimbria?

was it fro gram + or -?

A

The best studied fimbriae is the “P fimbriae” produced by uropathogenic E. coli.
gram -

48
Q

frimbrae vs flagella in gram -

A

In contrast to flagella, fimbriae of Gram‐negative bacteria grow from the base. The assembly requires two proteins: the chaperone and the usher (“the chaperone‐usher system”).

49
Q

how are the subunits in fimbriae assembled ?

How can adhesion be mediated?

A

• The subunits are assembled by strand exchange (like puzzle pieces).

Adhesion can be mediated by:
• the main subunits
• a specialized subunit at the tip (as is the case with the P fimbriae).

50
Q

Fimbriae of Gram+ bacteria:

1) adhesion?
2) assembly?

A

Gram + :
In Gram‐positives, adhesion to surfaces is generally carried out by surface adhesins, consisting of only one protein. Such adhesins mediate very close attachment.
Fimbriae of Gram‐ positive bacteria are assembled by sortases and attach to the peptidoglycan.

51
Q

Fimbriae of Gram‐positive bacteria vs Fimbriae of Gram‐negative bacteria

A 
Gram‐positive
• Anchoredinthe
peptidoglycan
• Composed of pilin proteins
• Covalently‐linkedtoone another
• Assembled enzymatically by sortases.

Gram‐negative
• Anchoredintheouter
membrane
• Composed of pilin proteins
• Notcovalentlyboundtoone another (strand exchange)
• Accessory proteins are needed, encoded with the fimbriae pilin genes.

52
Q

Formation of the endospore

A

As a cell begins the process of forming an endospore, it divides asymmetrically (Stage II). This results in the creation of two compartments, the larger mother cell and the smaller forespore. These two cells have different developmental fates. Intercellular communication systems coordinate cell-specific gene expression through the sequential activation of specialized sigma factors in each of the cells.

Next (Stage III), the peptidoglycan in the septum is degraded and the forespore is engulfed by the mother cell, forming a cell within a cell.

The activities of the mother cell and forespore lead to the synthesis of the endospore-specific compounds, formation of the cortex and deposition of the coat (Stages IV+V).

This is followed by the final dehydration and maturation of the endospore (Stages VI+VII).

Finally, the mother cell is destroyed in a programmed cell death, and the endospore is released into the environment. The endospore will remain dormant until it senses the return of more favorable conditions. [A sigma factor is a small protein that directs RNA polymerase to specific cites on DNA to initiate gene expression.]

53
Q

Germination:

what?

A

Germination involves the dormant endospore starting metabolic activity and thus breaking hibernation.

54
Q

Germination:

How is it characterized?

A

It is commonly characterised by rupture or absorption of the spore coat, swelling of the endospore, an increase in metabolic activity, and loss of resistance to environmental stress.

55
Q

When is germination triggered?

A

Reactivation of the endospore occurs when conditions are more favourable and involves activation, germination, and outgrowth. Even if an endospore is located in plentiful nutrients, it may fail to germinate unless activation has taken place. This may be triggered by heating the endospore.

56
Q

Where are energy reserves and building blocks are sometimes stored in bacteria and archaea?

A

granules or inclusions

57
Q

In some cases, the cell inclusions can be enclosed by ?

A

by a single layer membrane (phospholipid, protein, glycoprotein)

58
Q

Cell inclusion stores what types of nutrients?

A
  • Carbon
  • Sulfur
  • Polyphosphate
59
Q

What does cell inclusion confer?

A

buoyancy

60
Q

What allows the bacteria to respond to magnetic fields? Why is this relevant>

A

Magnetosome contains magnetite (Fe3O4) and allows the bacteria to respond to magnetic fields (magnetotaxis).
Know what is up and down (orient itself)

LSCI 230 (6 decks)

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