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MD2001 > Microbial Structure > Flashcards

Microbial Structure Flashcards

1
Q

What are the genetic differences between eukaryotes and prokaryotes?

A 
Eukaryotes: 
Have a true nucleus bound by double membrane
Linear DNA
DNA organised into chromosomes 
80s ribosomes
Prokaryotes: 
Do not have a nucleus: nucleoid instead but no physical boundary
Circular DNA
DNA naked (plasmids present however)
70s ribosomes
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2
Q

What are the structural differences between eukaryotes and prokaryotes?

A

Eukaryotes:
Cytoplasm filled with organelles
Mitochondria are energy centres
Transcription requires formation of mRNA and movement of mRNA from nucleus to cytoplasm for translation

Prokaryotes:
No membrane bound organelle
Mesosomes used in aerobic respiration
Transcription and translation occur simultaneously

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3
Q

What are the main structural components of bacteria ?

A 
Capsule 
Cell Wall
Pili
Flagellae
Spores
Slime
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4
Q

What is the capsule made of ? What is its function ?

A

Loose polysaccharide structure.

Protects cells from phagocytosis and dessication

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5
Q

What is pili made of ? What is its function ?

A

Made of oligomertic pilin proteins

Functions as appendage for bacterial conjugation (tube for transfer of plasmids between bacteria)

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6
Q

What is the role of fimbriae ?

A

Attachment of bacteria onto cell (thanks to lectins which recognize oligosaccharides on host cell)

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7
Q

What is the the flagellum made of ? What is its function ?

A

Made up of flagellin protein.

Function is locomotion thanks to rotary engine at anchor point on inner cell membrane.

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8
Q

What are the different types of flagella ?

A

Monotrichous - having a single flagellum
Amphitrichous - having flagella at each end.
Peritrichous - having a uniform distribution of flagella over the body surface
Lophotrichous - having two or more flagella at one end

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9
Q

What are spores ? What feature makes them hard to kill ?

A

Highly resistant, dormant structures triggered formed in response to adverse environmental conditions. Allows regrowth under suitable conditions.
Hard multilayered coats.

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10
Q

What are examples of diseases caused by sporing bacteria ?

A

Botulism due to clostridum botulinum

Tetanus due to clostridum tetani

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11
Q

What is slime made of ? What is its function ?

A

Slime is made by polysaccharide material.

Protects against immune attack and antibiotics, secreted by some bacteria growing in biofilm.

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12
Q

What are the distinctive features of gram positive bacteria ?

A
  • 2 layers (Peptidoglycan (PGN) layer in the cell wall + cytoplasmic membrane)
  • lipoteichoic acid (LPA) is the key protein
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13
Q

What are the distinctive features of gram negative bacteria ?

A
  • 3 layers (outer membrane phospholipid membrane + thin PGN layer + cytoplasmic membrane)
  • lipopolysaccharide (LPS) is the key protein
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14
Q

What are the steps of gram staining ?

A
  1. Primary stain (CRYSTAL VIOLET DYE)= stains all bacteria purple
  2. Trapping agent (Gram’s iodine)= Forms CVI complex in cell wall
  3. Decolorisation (alcohol/acetone)= interacts with lipids in the cell wall.
    Gram (-) loses outer LPS layer which exposes thin inner PGN. COLORS WASHED AWAY.
    Gram (+) becomes dehydrated and traps complexes in thicker PGN layer of cell wall. STAYS PURPLE.
  4. Counterstain (safranin):
    Turns Gram (-) pink/reddish
    Gram (+) stays purple
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15
Q

What is PGN made up of ?

A

Sugars and AAs

Sugar component = alternating residues of N-acetylglucosamine and N-acetylmuramic acid

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16
Q

What is lipoteichoic acid (LPA) made up of ? What is its role ? How does LPA of bacteria help the immune system?

A

Teichoic acid and lipds.
Provides cell rigidity.
Recognised by host immune cells.

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17
Q

What are the functions of LPS ?

A

Function in outer membrane
Elicits potent immune and inflammatory response
Produces endotoxins (toxins inside the cells, released when cell disintegrates)

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18
Q

What are examples of outer membrane proteins ?

A

Lipoproteins and porins.

19
Q

How do bacteria replicate ?

A

By asexual binary fission. Replication starts at origin of circular DNA —> 2 replication forks split from origin —>
The 2 replication forks meet at the bottom (bidirectional replication)

20
Q

What are the 4 phases of bacterial Replication ?

A

1) Lag phase: period of active growth (in size, not number), prepare for reproduction.
2) Log phase: Cell divides at maximum rate, uniform replication
3) Stationary phase: cessation of growth due to accumulation of inhibitory end products or O2 unavailability, number of cells dying = number of new cells
4) Death phase: Number dying cells exceeds number of newly born cells

21
Q

What is conjugation ?

A

One bacterium connects to other through pilus.

Geners transferred from one to other.

22
Q

What is transformation ?

A

Bacteria taking up DNA from their environment.

23
Q

What is transduction ?

A

Exchanging of bacterial DNA between bacteria through bacteriophages (virus infecting the bacteria)

24
Q

What are the shapes for bacteria ?

A

cocci (spherical), bacilli (helical), coccobaccili, spiral (helical rod)

25
Q

What are the possible atmospheric preferences for bacteria ?

A

Aerobic
Anaerobic
Microaerophillic (needs a little bit of O2)

26
Q

What are the components of viral stucture ?

A

Nucleic acid (ss DNA, ds DNA, ss RNA, ds RNA)
Capsid
Envelope (optional)
Spike (optional)

27
Q

What is the function of the capsid ? What are its components ? What are the possible shapes for capsids?

A

Shell for the virus. Composed of capsomeres.

Possible shapes: rod-like, polyhedral, complex

28
Q

What is the function of spikes ? What are its components ?

A

Attachment to cells + enzymatic/adsorption/haemagluttinin activity
Glycoproteins (highly antigenic)

29
Q

How does viral replication occur ? What are the steps to it ?

A

Uses host cell’s machinery to replicate.

  1. Adsorption (virus binds host cell, very specific)
  2. Penetration (virus injects genome into cell by fusion or binding or ingestion)
  3. Replication (Capsid digested bt enzymes and viral genome replicates)
  4. Assembly (viral components and enzymes are produced and begin to assemble)
  5. Maturation (virus fully develops)
  6. Release of naked viruses
  7. Release of envelopped viruses
30
Q

How does release of naked virus take place ?

A
  • Where ? Takes place at site of nucleic acid replication
  • How ? Viral enzymes break down bacterial cell wall
  • Who ? RNA viruses released as they are produced
  • Who ? DNA viruses expelled from host cell as the cell autolyse in inclusion bodies
31
Q

How does release of enveloped virus take place ?

A
  • Where ? Virus migrates to enter plasma membrane or nuclear membrane
  • How ? Envelopes form around nucleocapsids by budding of cell membrane
  • Slow continuous release of mature viral particles WITHOUT inclusion bodies
32
Q

How many cells do protozoa have ?

A

Unicellular

33
Q

What are the types of protozoa that exist ? What is the distinctive characteristic of each kind ?

A
  • Sporozoa (intracellular parasite)
  • Flagellates (have flagellae for movement)
  • Amoeba (have pseudopds for movement and feeding)
  • Ciliates (have cilia for movement)
34
Q

What is an example of protozoal infections ?

A

Malaria, Giardiasis

35
Q

What is the normal microbiota ?

A

Bacteria and fungi that live in our bodies.

36
Q

What are the structural features of fungi ?

A

Unicellular or multicellular

Chitin and glucans cell wall

37
Q

How do fungi reproduce ?

A

Asexually by budding (sometimes by binary fission)

38
Q

What is the other name for fungal infections ?

A

Mycoses

39
Q

What are examples of fungal infections ?

A

Ringworms (tinea corporis and tinea pedis), candidiasis (due to Candida Albicans)

40
Q

What are the main Helminths groups (parasitic worms) ?

A

Tapeworms (Cestoda)
Roundworms (Nematoda)
Flukes (trematoda)

41
Q

Which part of the body do helminths usually infect ?

A

The intestine

42
Q

How are helminths transmitted ?

A
  1. Via intermediate host (like pork)
  2. Injection by blood-sucking insect
  3. Fecal oral route
  4. Active skin penetration
43
Q

What are examples of infections by helminths ?

A

Tapeworm due to Taenia Solium (has scolex for attachment). Large intestine.
Schistosmoiasis (=bilharzia) due to flukes. Affects urinary system and intestines.

MD2001 (35 decks)

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