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Infection and Immunity > Bacteria 1,2 > Flashcards

Bacteria 1,2 Flashcards

1
Q

draw bacterial cell diagram

A
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2
Q

name 4 external structures of bacterial cells

A

glycocalyces, flagella, fimbriae, pili

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3
Q

what is glycocalyces and what is its function in the bacterial cell

A

-sticky external layers/capsule
-prevents cell drying out, protects from phagocytosis, cell to cell adherence

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4
Q

what is flagella and what is its function in the bacterial cell

A

-long whip protrusions composed of basal body, hook and filament
-allow movement towards nutrients or away from toxins, singular or covers whole cell

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5
Q

what is fimbriae and what is its function in the bacterial cell

A

-extensions of some bacterial cells
-cell to cell adherence, cell surface adhesion and movement

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6
Q

what is pili and what is its function in the bacterial cell

A

-hollow, non motile tubes of protein
-bacterial cell movement for cell to cell contact, movement of DNA from one cell to another

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7
Q

what is cytoplasmic membrane

A

phospholipid bilayer, contains proteins, selectively permeable to allow passage of molecules

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8
Q

describe the movement across cytoplasmic membrane

A

across concentration and electrical gradients, passive diffusion, facilitated diffusion and active transport

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9
Q

describe the features within a bacterial cell

A

cytoplasm- composed of liquid cytosol
nucleoid= nuclear region in prokaryotes, no membrane, singular circular molecule of DNA
inclusions- deposits of substances in cell
ribosomes- composed of proteins and rRNA for protein synthesis (70s)
cytoskeleton- network of fibrils that maintain shape of cell

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10
Q

difference between gram positive and gram negative

A

gram positive= thick layer of peptidoglycan (cell wall)
gram negative= thin layer of peptidoglycan, external wall membrane with periplasmic space in between, contains LPS with lipid A

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11
Q

describe the function and composition of cell wall

A

provides shape, protects against osmotic pressure

composed of interconnected polysaccharide chains of peptidoglycans (polymer of glycan crosslinked by short peptide chains), composed of alternating sugar molecules of NAG and NAM

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12
Q

what is a microbiome

A

ecological community of commensal, symbiotic and pathogenic microorganisms

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13
Q

function of microbiome in human health

A

protects body, important in maturation and development of immune system, performs biochemical functions, disruption of balance leads to colonisation or overpopulation of certain microbes leading to infections/diseases

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14
Q

describe the microbiome of the GI tract

A

most bacteria in lower GI tract, most dense and complex, hundreds of species of bacteria, archea, fungi

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15
Q

function of microbiome in GI tract

A

-digest materials by producing enzymes the host doesnt and provides important nutrients
-compete with pathogenic microorganisms
-reduce risk of colonisation of pathogens by removing nutrients or changing pH
-influences immune system to improve response to pathogenic bacteria

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16
Q

what is the difference between probiotic and prebiotic

A

probiotic= tiny health promoting organisms that reside in gut (like yeast and bacteria)

prebiotic= indigestible food ingredients that act as food for probiotics

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17
Q

why do infections make us ill

A

pathogens- disease causing microorganisms
infection- pathogenic bacteria grow in host
virulence- ability of pathogen to cause disease
virulence factors- produced by microorganisms, aids colonisation
disease- damage from infection
invasive- bacteria multiply rapidly to establish an infection

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18
Q

what is virulence and virulence factors

A

virulence= ability of pathogen to cause disease

virulence factors= produced by microorganisms that aid colonisation

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19
Q

name some routes of entry of bacteria into the body

A

respiratory tract, gastrointestinal tract, urogenital tract, breaks in skin surface, ingestion of contaminated food, faeces containing pathogenic microbe

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20
Q

how does bacteria establish an infection

A

entry, attachment, invasion

21
Q

how does bacteria attach to host cells

A

-direct protein protein interaction
-indirect interaction with capsule/slime
-fimbriae and pili on external surface of bacteria

22
Q

describe the 3 different types of toxins made by bacteria

A

exotoxins-

enterotoxins-

endotoxins-

23
Q

what is gastroenteritis, symptoms and causes

A

inflammation of gastrointestinal mucosa/intestinal lining that involves stomach and small intestine

symptoms= diarrhoea, vomiting, abdominal pain, cramps

causes= viral/bacterial infection, eating contaminated food, people contact

24
Q

what are the two main bacteria that cause gastroenteritis

A

salmonella- non bloody diarrhoea, nausea, vomiting, produces protein that induces phagocytosis, rearrange cytoskeleton and induce apoptosis of infected epithelial cells

campylobacter- inhabits intestinal tract of poultry and cattle, can be killed by heat, treatment is electrolyte replacement and rehydration, antimicrobial treatment only when bacteria is invasive or used to eliminate carrier

25
Q

how does bacteria synthesise cell wall

A
  1. peptidoglycan biosynthesis in cytoplasm
  2. transport of peptidoglycan across cell membrane via lipid carrier
  3. insert and crosslink of peptidoglycan in cell wall
26
Q

why is cell wall biosynthesis a target for antibiotic therapy

A

mammal cells dont have cell walls so antibiotics will have selective toxicity and only attack virus cells

27
Q

what are characteristics of β-lactam family of antibiotics

A

inhibits transpeptidase enzymes, broad spectrum antibiotic

28
Q

what does broad spectrum mean in antibiotics

A

effective against both gram positive and negative

29
Q

how do β-lactam antibiotics selectively inhibit bacterial cell wall synthesis

A

inhibits transpeptidase enzymes which is involved in peptidoglycan synthesis, mimics D-alanyl-D-alanine residues

β-lactam ring broken but remaining molecules bind to enzyme for short period to cause brief inactivation leading to destabilisation of cell causing cell wall to be leaky and eventually osmotic burst

30
Q

what does β-lactam antibiotics mimic

A

D-alanyl-D-alanine residues

31
Q

what do β-lactam antibiotics do

A

inhibit transpeptidase

32
Q

describe the resistance mechanisms of bacteria to β-lactam antibiotics

A

production of β-lactamases cause resistance to β-lactams, this causes ring opening/drug cleavage at β-lactam ring

33
Q

describe 2 other resistance mechanisms

A

target modification- PBP mutations (penicillin binding proteins)

reduced uptake- change of porin permeability

34
Q

how does gram positive and gram negative bacteria develop resistance to β-lactam antibiotics

A

gram positive= develops high MW PBP with lower affinity to antibiotics (MRSA)

gram negative= reduction of permeability of outer membrane channels (porins) and development of high MW PBP with lower affinity of antibiotics

35
Q

what is PBP

A

penicillin binding proteins

36
Q

what is the target of β-lactam antibiotics

A

PBP/transpeptidase

37
Q

what is β-lactamase production a result from

A

genetic transfer and subsequent expression of enzyme

38
Q

what are β-lactamase enzymes

A

hydrolases that cause ring opening of β-lactam ring

39
Q

name 2 ways to stop β-lactamase activity

A

cephalosporins and use of lactamase inhibitors like clavulanic acid and amoxicillin

40
Q

how does clavulanic acid inhibit β-lactamase

A

clavulanic acid has a β-lactam ring which acts as a target for the enzyme which binds to the molecule and inhibit the enzyme

41
Q

what can inactivate all β-lactam antibiotics

A

mutant lactamases

42
Q

how are mutations transferred to other bacteria

A

conjugation

43
Q

what does acylation of penicillin nucleus results in

A

number of penicillin with different side chains with different antibiotic spectrums

44
Q

what are ESBLs

A

ESBLs= extended spectrum beta lactamases
enzymes that can be made by bacteria making them resistant to many antibiotics

45
Q

what are porins

A

channel proteins in outer membrane of gram negative bacteria that allows diffusion of small nutrients and antibiotics

46
Q

what is the main entrance pathway of E. coli

A

porin Ompf

47
Q

how is porin dependent resistance mediated

A

decreased porin expression (less porins) or mutations affecting permability

48
Q

how does resistance mechanisms arise

A

genetic transfer of DNA that encode for modified enzymes or porins

Infection and Immunity (6 decks)

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