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Microbiology > Prokaryotes > Flashcards

Prokaryotes Flashcards

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Biology 101 flashcards
1
Q

What are the domains of Prokaryotes?

A

Archaea. Bacteria.

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2
Q

Describe the Coccus shape?

A

Round or roundish

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3
Q

Describe the bacillus shape?

A

Rod

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4
Q

Describe the Spirillum/Spirochete shape?

A

Curved from

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5
Q

What is the Coccobacili shape?

A

Between coccus and a rod

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6
Q

What is the cell structure of a prokayote?

A

Cell membrane. Nuceloid. No real internal structures. Flagellum

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7
Q

What are the cell membranes in Prokaryotes?

A

Phospholipid bilayer (usually).

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8
Q

What is the cell envelope?

A

The cell wall and the cell membrane

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9
Q

What is the cell wall in a Prokaryote?

A

Peptidoglycan/muerin. Made up of alternating links o 2 amino sugars (NAG and NAM). Linked in long repeating chains with cross links.

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10
Q

What is the difference in the cell wall of archaea?

A

N acetyltalosaminuronic acid. Different amino acids. All L amino acids in side chain.

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11
Q

What can most bacteria be categorised into?

A

Gram-positive and Gram-negative

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12
Q

What are the properties of Gram-positive?

A

Peptidoglycan. Membrane

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13
Q

What are the properties of Gram-negative?

A

Peptidoglycan. Membrane. Outer (lipopolysaccharide). Periplasm

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14
Q

What are the properties of cell envelopes in archaea?

A
  • Phospholipid monolayer
  • Single molecules
  • Biphantyl, makes it much stronger
  • Must have a layer protein
  • Rigid wall of meurin like compound
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15
Q

What are the ‘internal’ structures of prokaryotes?

A

Nucleoid. Ribosomes. Cytoskeleton. Intracellular granules. Spores.

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16
Q

Describe the structure of the nucleoid.

A
  • DNA, bound in the cell
  • Single circular chromosome
  • Plasmid, circle DNA, carries genes not essential
  • Plasmids can be taken up and injected
  • DNA coiled round proteins
  • Plasmid supercoiled
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17
Q

Describe the structure of ribosomes.

A

Lots and lots of ribosomes. Slightly different eukaryotic. 30S and 50S components

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18
Q

Describe the structure of Cytoskeleton

A
  • Formed by polymeric proteins
  • Filamentous structures
  • Maintains cell shape, motility and molecules trafficking
  • MreB, ParM and FtsZ (protein)
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19
Q

WHat does FtsZ do?

A

Important in cell fivision. Forms a ring mid cell and attracts proteins to that side.

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20
Q

Describe the function granules.

A
  • Storage of granules
  • Polymeric reserves of nutrients
  • Mostly glucose (glycogen)
  • Magnetosomes
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21
Q

What are magnetosomes?

A

Granules of magnetic material enclosed in a membrane. Acts like a compass

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22
Q

Describe the function of spores.

A

Survival structures. Spores formed within the cell

  • Endosperms
  • Can survive harsh conditions
  • Bacteria can shut down (hibernate)
  • Can kill, autoclave at 120 degrees
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23
Q

What are the ‘external’ structures of prokaryotes?

A

Glycolcalyx. Capsules. Pili and fimbriae. Flagella

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24
Q

What is glycocalyx?

A

Loose network of fibrils. Slime layer (sticky). Glycoprotein. Helps adherence of bacteria to surfaces.

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25
Q

What are capsules?

A

Polysaccharide material. Thick gelatinout layer outside cell wall. Helps pathogenic bacteria to invade the host.

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26
Q

What is Pili and fimbriae?

A
  • Organised structure
  • Play a role in adherence
  • Fimbriae = hair like, sticks to things
  • Pili = attach bacteria together for conjugation
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27
Q

What is flagella?

A
  • Used for locomotion
  • Hollow tube composed of protein
  • Flagella rotates and allows movement
  • Different arrangements
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28
Q

How do prokaryotes reproduce?

A

Binary fission

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29
Q

Describe binary fission?

A
  • Cell growth, B or G1 period
  • Chromosome replication, C period
  • Septum formation and cell division, D period
  • Separates into two equal sized daughter cells
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30
Q

What protein is binary fission initiated by?

A

FtsZ

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31
Q

Describe the role of FtsZ in binary fission

A
  • Acts as an organiser protein
  • Focal point for everything else in cell division
  • Forms a polymer ring around the equator where the cell will divide
  • In presence of GTP acts as the point to get this process to happen
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32
Q

How does FtsZ know where midcell is?

A
  • Controlled by complex protein system
  • MinCDE system, series of proteins
  • Makes sure FtsZ goes to the right place
  • MinCDE system repeatedly builds up and is broken down in polar parts of the cell
  • Components shuttle to the other end of the cell and build up and break down
  • MinC prevents Z ring formation
  • High conc. at the ends so more FtsZ in the centre
33
Q

How is peptidoglycan made?

A

Bactoprenol takes building blocks across the cytoplasmic membrane. Transglycosylases catalyses insertion of the precursor in the growing point of the cell wall and catalyse glycosidic bond formation.

34
Q

What is the carrier molecule in the production of the cell wall?

A

Bactoprenol

35
Q

Where is the septum placed?

A

Located between the 2 newly replication chromosomes. Everything needs to be in the right position before septum is formed

36
Q

How do bacterial chromosomes replicate?

A

Bidirectionally from a single origin

37
Q

Where is the origin that chromosomes start to replicate?

A

Region where special DNA sequences are repeated.

38
Q

Describe the process of chromosomal replication

A
  • Starts at origin
  • Initiation protein called DnaA (binding of multiple copies_
  • Bending the DNA in a loop
  • Replication proteins add to this complex forming two replisomes (replication forks)
  • Termination of replication is when replisomes reach a special region = the terminus
39
Q

What do interdivision times depend on?

A

Rich environment = fast. Poor environment = slow growth = long interdivision

40
Q

Describe the time periods of the different stages in binary fission

A

B/G1 is variable. C phase and D phase are always the same. Cell cycles can overlap.

41
Q

What is a rich medium?

A

Contains organic compounds. Want to grow as much as possible. Amino acids, vitamins, purines.

42
Q

What is a minimal medium?

A

Want to see if a microorganism can grow on something specific. Only capable of growing with a compound. Has everything but a carbon source.

43
Q

What is a broad medium?

A

Medium based on meat or yeast. Eg nutrient broth. Like rich medium.

44
Q

What is a selective medium?

A

Only allow certain organisms to grow because it supresses out others. Promote growth of some bacteria and inhibits others.

45
Q

What is a spectrophotometer?

A

Shines light of a known wavelength and determines the amount of light that gets through

46
Q

What are some ways of measuring the amount of bacteria?

A

Dilutions or plate count

47
Q

How do you do serial dilutions?

A

Take 1ml of culture 9ml broth. Dilute down by a factor of 10. Each dilution = less colonies. Count the one between 30 and 300, Multiply by dilution factor. Calibration curve and colonies

48
Q

How do you work out the colonies from plate count?

A

If you know start number and growth.

N = N0*2(^n)

49
Q

How can a batch culture be modelled?

A

With a bacterial growth cruve

50
Q

What is a batch culture?

A

Inoculated and left to grow

51
Q

What is continuous culture?

A

Constantly adding and removing nutrients

52
Q

What is the lag phase?

A

Taking time for bacteria to adjust to their environment

53
Q

What is the log phase?

A

Rapid increase over time governed by growth conditions

54
Q

What is the stationary phase?

A

Something starts to limit this process, growth stops

55
Q

What is the death phase?

A

Can’t survive so they die, become toxic, happens slowly as the dead bacteria release their contents. Others can feed off the contents and survive for slightly longer.

56
Q

Give some examples of when bacteria can be beneficial and/or harmless.

A

Protection against colonisation by harmful bacteria. Production of antimicrobial compounds. Synthesis of vitamins. Stimulation of production of natural antibodies

57
Q

When can bacteria turn from harmless to harmful?

A

Oppurtunistic. In immunocompromised patients. If you have a wound eg the result of surgery.

58
Q

What is a pathogen?

A

Microorganisms that are able to cause disease in animals, plants or insects

59
Q

What 2 mechanisms allow pathogens to get round our defenses?

A

Invasiveness and toxigenicity

60
Q

What is virulence?

A

How rapidly bacteria cause infection

61
Q

What is invasiveness?

A

Ability of a pathogen to invade the body, spread and establish an infection

62
Q

What is colonisation?

A

Adherence and initial proliferation

63
Q

What are bacterias routes of entry?

A
  1. Inhalation (air)
  2. Ingestion (food/water)
  3. Contact
  4. Bile
64
Q

How does E.coli stick?

A

Uses pili and fimbriae.

  • Type 1 fimbriae bind mannose on surface
  • Ability to encode different fimbriae to associate with different host cells
  • End of fimbriae
65
Q

What are the 2 types of toxins bacteria can produce?

A

Exotoxins and endotoxins

66
Q

How do exotoxins work?

A

Damage by producing toxic chemicals. Usually digestive enzymes that are secreted and destroy cellular structures.

67
Q

What do does cytotoxin cause?

A

Diptheria toxin

68
Q

How do cytotoxins work?

A

Damages cell affecting throat. Binds to epithelial cells. Prevents protein synthesis

69
Q

What do neurotoxins cause?

A

Botulinum and Tetanus.

70
Q

How does the botulinum toxin work?

A

Prevents release of acetylcholine in synapses. Nerves don’t work anymore. Difficulty breathing and maintaining heartbeat leads to paralysis. Most acutely lethal toxin known.

71
Q

How does the tetanus toxin work?

A

Tetanus (lockjaw). Puncture wound. Doesn’t like aerobic conditions. Blocks release of inhibitory neurotransmitters at synaptic cleft so muscles fire and can’t switch off = becomes rigid.

72
Q

Describe the subunits A and B in exotoxins?

A

Subunit B = binds to receptor. Subunit A = can transfer directly into the cell or taken up through phagocytosis

73
Q

Describe how an endotoxin works.

A
  • Components of the cell envelope
  • Gram negative
  • Attached to bacterial cell
  • Immune system rescognises and responds causing the symptoms
74
Q

What is the bacterial pathogen vibrio cholera?

A

Causes cholera. In water. You lose water rapidly = dehydration. Produces a toxin

75
Q

What is the bacterial pathogen yersinia pestis?

A

The plague. Rod shaped, gram negative. Vector borne. Haemorrhaging of lymph nodes. Buboes = bubonic plague. Inhalation = pneumonic plague

76
Q

What are antibiotics?

A

Can kill or inhibit the growth of microorganisms but wont kill.

77
Q

How do antibiotics work?

A

Interfere with bacteria specific biological processes eg cell wall synthesis, cell membrane structure or protein synthesis

78
Q

What is the problem with antibiotics?

A

Bacteria can develop resistance that was previously killing them

79
Q

How do bacteria gain resistance?

A

Chromosomal mutation or acquisition of a plasmid encoding resistance from a resistant bacteria. Can become resistant to multiple antibiotics

Microbiology (8 decks)

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