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susom idr > Microbes and Bacterology > Flashcards

Microbes and Bacterology Flashcards

1
Q

What makes an infectious organism harder to target

A

the more cellular structures we have in common

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2
Q

Why are viruses not shown on the tree of common ancestors?

A

they require a host to replicate

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3
Q

In terms of size how big is a prokaryote compared to the smallest eukaryotic cells?

A

it’s about half the size. 5μm. where eukaryote is 10μm

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4
Q

What shape are cocci?

A

spherical-shaped

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5
Q

what shape are staphylococci?

A

bunches like grapes

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6
Q

what shape are streptococci?

A

lines like beads on a string

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7
Q

what shape are bacilli?

A

rod shaped

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8
Q

What shape are vibrio

A

comma-shaped/slightly curved

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9
Q

What shape are fusiform bacilli?

A

long, slender rod

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10
Q

what shape are spirilla?

A

curving rod, NOT a corkscrew

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11
Q

What shape are spirochete?

A

helical/corkscrew-shaped, very slender rod

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12
Q

A typical bacillus is 3μm long, how small is the small pox virus?

A

.3x.2x.1μm. polio virus is .003μm

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13
Q

How can we use a bacteriaphage in the lab?

A

to target bacteria and to transfer genes b/w them

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14
Q

What are the only layers in a non-enveloped virus?

A

nucleic acid and capsid (made of capsomere)

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15
Q

Give an example of a non enveloped virus and why is it more stable than an enveloped virus?

A

polio, b/c it’s so simple, it is easier to transfer from person to person. FYI polio can be transmitted in water

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16
Q

How does a non-enveloped virus attach to cells?

A

structures in the capsid

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17
Q

why are enveloped viruses easier to sterilize/disable compared to non-enveloped viruses?

A

the lipid bilayer from is usually derived from the host. The lipid bilayer is sensitive to desiccation (drying out), heat, alcohol, detergents. typically must transfer from host to host.

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18
Q

what is found on the outside of enveloped viruses?

A

glycoproteins and a lipid bilayer

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19
Q

give an example of an enveloped virus

A

HIV– bodily fluid transfer

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20
Q

what form is a helical nucleocapsid typically found?

A

nonenveloped

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21
Q

how does a virus replicate?

A

inside a host cell. viral surface binds to proteins on host cell and are engulfed.. cells know they are infected and signal the immune system to kill them

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22
Q

what is the whole strategy for survival of enveloped proteins based around?

A

glycoproteins being the receptors for the host cells.

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23
Q

the genome components of viruses can be targeted by the immune system. What is unique to viruses along the lines of nucleic acids?

A

Viruses have double stranded RNA- this is a good target for the innate immune system.

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24
Q

What are some of the roles of “normal flora” or “microbiota”?

A
  • Digest food
  • synthesize vitamins
  • compete against pathogens
  • immune tolerance for normal bacteria
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25
Q

What is used as the gold standard to identify bacteria to the species level?

A

16s rRNA sequencing on the SSU

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26
Q

TLR 5 target:

A

Flagellin (outside)

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27
Q

TLR 4 target:

A

Lipid A of LPS (outside)

28
Q

TLR 2 + TLR 6 targets:

A 
lipoteichoic acid (LTA) (gram positive).
Mannose-conjugated proteins in fungi (outside)
29
Q

TLR 1 + TLR 2 target:

A

Bacterial lipoproteins (outside)

30
Q

TLR 3 target:

A

dsRNA (vesicular target)

31
Q

TLR 7, TLR 8 target:

A

endosomal RNA (vesicular target)

32
Q

TLR 9 target:

A

unmethylated CpG motifs in DNA (vesicular target)

33
Q

NOD 1 Target:

A

peptidoglycan alanine bridges (my cytoplasm)

34
Q

NOD 2 target

A

n-acetyl-muramic acid (NAM) (my cytoplasm)

35
Q

mechanism of lysozyme on peptidoglycan

A

cleaves the glycan backbone of the peptidoglycan. bacteria will succumb to the large osmotic pressure and lyse.

36
Q

how many layers of peptidoglycan does gram-positve have?

A

lots! up to 30 layers

37
Q

destruction of peptidoglycan would be more effective on which bacteria?

A

gram positive. peptidoglycan is the outermost layer

38
Q

describe gram negative cell wall from the inside out

A
  • plasma membrane (phospholipid bilayer)
  • cell wall <5 layers of peptidoglycan
  • Outer membrane, phospholipids on one side and LPS on the other
  • Porin proteins make holes in the OM– very small not everything gets in.
39
Q

what is contained in the periplasmic space?

A

gram- negative: transport components for iron, proteins, sugars, and other metabolites. enzymes that include proteases, phosphatases, lipases

40
Q

what are the three components of the endotoxin LPS?

A

Lipid A, core polysaccharide (rough core), and O-antigen.

*the core region is the same a species of bacteria.

41
Q

what do porins let in?

A

diffusion of hydrophilic molecules less than 700 da through the membrane

42
Q

why are polymyxins primarily used externally?

A

they can cause serious nephrotoxicity.

43
Q

Polymyxins B and Colistin

A

insert into bacterial membranes like detergents, by interacting with LPS and phospholipids in the OM, producing increased permeability and death. gram-negative.

44
Q

why is vancomycin not useful against gram-negative bacteria?

A

the holes in the OM are too little for the drug to get into to access the peptidoglycan and block the two D-ala from linking to form the NAG-NAM chain. give with an IV

45
Q

why would a human cell stain with safranin?

A

gram stain relies on the ability to bleach the purple color out. we don’t have peptidoglycan

46
Q

what is the enzyme that links the two NAMs forming a bridge across layers?

A

transpeptidase

47
Q

how do beta-lactam antibiotics work?

A

the ring is so similar to the D-alanine-alanine motif that is cross-linked in the peptidoglycan cell wall. the enzyme that crosslinks the alanines can bind to beta lactam ring instead, disabling it.

48
Q

what is the difference b/w 1st & 2nd generation beta-lactams?

A

1st: destroyed by beta-lactamases
2nd: resistant to beta-lactamases

49
Q

what is the benefit of mycolic acid?

A

on mycobacterium spp. b/c of its waxiness it protects bacteria from drying out, phagocytosis, and to some extent antiseptics

50
Q

what drugs are acid-fast bacterial susceptible to?

A

isoniazid and pyrazinamide- they inhibit mycolic acid synthesis

51
Q

what is the stain used in acid-fast staining?

A

carbol fuchsin and methylene blue

52
Q

why could you have vaccine for a bacterial capsule type and still become infected from it?

A

bacteria can make more than one capsule type.

53
Q

where is capsule?

A

on both gram negative and gram positive. deposited on the otherwise outermost layer. produced by individual bacteria

54
Q

advantages of capsule:

A
  • avoid phagocytosis
  • prevent drying out- sugar layer pull h2o from environment
  • inhibit effective adaptive immune response
  • carbohydrates are poorly antigenic
  • capsule type switching (serotype)
55
Q

During which phase of the growth curve are sporulation genes expressed at the highest levels?

A

Stationary phase

56
Q

Metronidazole can be used against…

A

obligate anaerobes (regardless of gram-stain status) or even if they’re not bacteria.

57
Q

When is metronidazole contraindicated?

A

when taking with alcohol –> flushing, nausea, high pulse

58
Q

How does metronidazole work?

A

reduced by ferredoxin (an iron storage molecule) in cells (bacteria and eukaryotes). RNS that anaerobes can’t deal with.

59
Q

bacteria that can Sort of break down RBCs on blood agar

A

alpha hemolytic– green color– also why stool is sometimes this color

60
Q

bacteria that lack hemolysis on blood agar

A

gamma hemolytic- maybe a very light brown color

61
Q

bacteria that completely break down RBCs on blood agar

A

beta hemolytic- would show underlying media color

62
Q

What do pin prick colonies around beta hemolysis on a blood agar indicate?

A

these are colonies that need components of RBCs but are unable to break them down on their own

63
Q

What is chocolate agar

A

agar with lysed blood cells, used to grow bacteria that need blood cell component but can’t break down RBCs

64
Q

What do the antibiotic sulfonamides inhibit?

A

folate synthesis

65
Q

How does the antibiotic trimethoprim work?

A

stops reduction of dihydrofolate to tetrahydrofolate

susom idr (3 decks)

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