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Proteins > Bacteria > Flashcards

Bacteria Flashcards

1
Q

What are the biggest pathogenic species?

A

Bacteria: 538/1400

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2
Q

How are bacteria useful?

A

Ecosystems
Food production
Useful materials

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3
Q

What are the harmful effects of bacteria?

A

Disease
Food spoilage
Biofouling and corrosion

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4
Q

What are Koch’s postulates?

A

Present in every diseased organism
Can be isolated and purely grown
Reintroduction causes disease
An identical species can be re-isolated

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5
Q

Which postulate has been re-evaluated?

A

Pathogens can be found assymptomatic/aquire virulence/non-pathogenic in healthy organisms too

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6
Q

When are opportunistic pathogens active?

A

In deep tissues or immunocompromised people

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7
Q

How many pathogens can cause each disease?

A

Multiple

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8
Q

Where is normal flora rich?

A

GI,
urogenital tract
nose
skin

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9
Q

What is the function of the human microbiome?

A

Provides colonisation resistance

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10
Q

What type of infections do the normal flora cause?

A

endogenous

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11
Q

What are the major disease causing normal flora?

A

Endogenous opportunistic

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12
Q

What are exogenous infections?

A

Pathogens aquired from other organisms

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13
Q

What percentage of human disease causing pathogens are zoonoses?

A

60%

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14
Q

What type of pathogen is Mycobacterium tuberculosis?

A

an exogenous infection

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15
Q

What symptoms does TB have?

A

Non-specific lung damage including granulomas, necrosis and fibrosis

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16
Q

What form is TB commonly found?

A

Latent infection in a third of the worlds population

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17
Q

What type of infection is Pneumonia?

A

exogenous

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18
Q

What does pneumonia cause?

A

Build up of bacteria and WBCs in lungs reduces O2 uptake

Systematic infection has poor mortality

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19
Q

Which pathogen has synergy with influenza?

A

Pneumonia

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20
Q

What increase does HIV cause in TB activation?

A

800 fold

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21
Q

What are the 2 types of food poisoning?

A

exotoxin produced by pathogen after ingestion or on food

endotoxin are part of pathogen

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22
Q

What type of food poisoning causes cholera?

A

Exotoxin produced in intestine by Vibrio cholerae

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23
Q

How do endotoxins cause disease?

A

lipopolysaccharide in gram negative capsule
Lipid A portion binds to membrane
LPS binds to LBP, activating macrophages
Septic shock

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24
Q

What are the symptoms of septic shock?

A 
Fever, 
coagulation
hypotension
inflammation
organ failure
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25
Q

How do endotoxins spread?

A

Lysis of envelope spreads fragments through bloodstream

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26
Q

Which kingdoms do not have cell walls?

A

protozoa

animals

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27
Q

What is the function of cell walls?

A

Protect cell from hypertonic environments/osmotic stress

Provide anchorage from proteins to interact with extracellular environment

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28
Q

What is the bacterial cell wall made out of?

A

Peptidoglycan/murein mesh with 2nm pores

29
Q

What is the structure of peptidoglycan?

A

NAG-NAM glycan strands

Cross links between NAM

30
Q

How are cross links formed from NAM stem peptides?

A 
muramic acid
L ala 
D Glu
Mesodiaminopimelate ------ D ala
D ala
31
Q

Which organisms have indirect cross links between NAM?

A

penicillin resistant strains

32
Q

Which stem peptide residue is highly conserved?

A

D-ala

33
Q

How is peptidoglycan synthesised?

A

D-ala-D-ala synthesised by racemase and ligase
D-glu synthesised by racemase
UDP NAM pentapeptide dervived from F6P by MurA-F
MraY attaches NAM to undecaprenyl phosphate on membrane
MurG attaches NAG to NAM
Transfer across bilayer
Penicillin Binding Proteins cause transglycosylation onto existing glycan and transpeptidisation using energy provided by cleavage of pentapeptide

34
Q

What is the structure of the cell wall in Gram negative bacteria?

A

Thin layer of PG tethered to capsule by Braun’s lipoprotein

35
Q

What is the structure of the gram positive bacterial cell wall?

A

Thick cell wall with techoic acids binding proteins and lipotechoic acids anchoring to cell membrane

36
Q

What cell wall do chlamydiae have?

A

Cysteine rich P layer

37
Q

What cell wall do archaebacteria have?

A

S layer or pseudo-peptidoglycoprotein

38
Q

What organisms have a chitin cell wall?

A

Fungi

39
Q

Why are chlamydiae susceptible to antibiotics targetting Peptidoglycan?

A

Peptidoglycan scaffold/cytoskeleton

40
Q

What are the 3 ways PG is recognised by the immune system?

A

intracellular,
soluble
extracellular

41
Q

What are the extracellular recognition mechanisms for PG?

A

CD14 and TLR2 receptors trigger cytokine cascade

42
Q

What are the intracellular recognition mechanisms for PG?

A

NOD1 detects Mesodiaminopimelate from gram negative bacteria

NOD2 inimmune cells detects NAM-ala-glu

43
Q

What are the soluble receptors of PG?

A

CD14 and C-type lectins

Activate complement cascade

44
Q

How do some bacteria reduce competition?

A

Produce lysostaphin metalloendopeptidase to cleave serine residues in other organisms

45
Q

What are antibacterial drugs?

A

Drugs produced that are selectively toxic to bacterial cells

46
Q

How are antibiotics produced?

A

Secondary metabolites of fungi and bacteria

47
Q

What are the 2 main classes of antibacterial agents?

A

Bacteriostatic

Bacteriocical

48
Q

How do antibacterials selectively target cells?

A

Differences in metabolism to convert prodrugs
Cannot enter mammalian cells
Target absent/modified processes in bacteria

49
Q

What are the main mechanisms of antibacterial action?

A

Steric hindrance
Substrate analogs
Enzyme inactivation
Disruption/subversion

50
Q

What are most antibacterials?

A

Antibiotics

51
Q

What are the main targets of antibacterials?

A 
DNA
Cell wall
Cell membrane
Nucleotides
Transcription
Translation
52
Q

Which antibacterial agents target the Cell wall synthesis?

A 
β lactams
fosfomycin
vancomycin
bacitracin
D-cycloserine
Isoniazid & ethionamide
53
Q

Which drugs target the cell membrane?

A

polymgoxin B&E

Daptomycin

54
Q

Which antibacterials target nucleotides?

A

Sulphonamides

Trimethoprim

55
Q

What do Fluoroquinones and quinolones target?

A

DNA intercalation

56
Q

What does rifamicin target?

A

transcription

57
Q

What drugs target translation?

A 
Linezoid
Fusidic Acid
Mupirocin
Tetracyclines
Chloramphenicol
Streptomycin
Erthyromicin
58
Q

What is antibacterial agent resistance?

A

The ability of bacteria to survive and grow in the presence of an antibiotic concentration that can be safely achieved at the site of infection in humans

59
Q

What social effects does antibiotic resistance have?

A

Increased mortality
Increased morbidity
Increased cost

60
Q

How can bacteria develop resistance?

A

Intrinsic resistance caused naturally

aquired resistance through horizontal transfer or spontaneous mutation

61
Q

What are the mechanisms of drug resistance?

A 
Alteration to target structure
Change in quantity of target
Decreased permeability
Increased efflux
Enzymatic inactivation
Acquisition of an alternative target for bypass
62
Q

How many resistance mechanisms can a bacterium show?

A

Multiple

63
Q

What are examples of resistance by target acquisition?

A

PBP2a variant in MRSA

64
Q

What are examples of target structural alteration causing resistance?

A

RNA polymerase point mutation blocking Rifamicin
CFR methylase aquired to act on ribosome
Mutated PG terminal blocking vancomycin

65
Q

What resistance does VISA have?

A

Thickened cell wall so vancomycin can’t reach new PG

66
Q

How can efflux-induced drug resistance be caused?

A

Upregulation of existing transporter or acquisition of new target

67
Q

Which type of resistance is produced by β lactamases?

A

enzymatic inactivation of antibiotic

68
Q

How are aminoglycosides modified in drug resistance?

A

adenylation, hydroxylation or phosphorylation

69
Q

How can antibacterial resistance be prevented?

A

develop new antibiotics
recycling
improved control of infections
restriction of use

Proteins (12 decks)

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