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AD2 > Bacteria > Flashcards

Bacteria Flashcards

1
Q

What are the different collony shapes of Cocci and Rods?

A

Cocci - single, chains, pairs, clusters, 4s and 8s

Rods - single, chains, curved, club shaped, pairs, helical, filamentous

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2
Q

What is the Bacterium plasma membrane made of?

A

-hopanoids-stabilise membranes
-proteins
-carbs

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3
Q

What is the structures of a Gram positive bacteria cell wall?

A

-thick layer of peptidoglycan
-permeable, can let things through

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4
Q

Whats the advantages of being Gram +ve or -ve?

A

+ve - evade desiccation
-ve - evade complaments

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5
Q

What is the structures of gram -ve bacterium?

A

Single layer of peptidoglycan
second outer membrane with lipopolysaccharide -retain water

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6
Q

What does lipopolysaccharides (O-antigen) do?

A

protects agains complements and MAC - act as immune defence

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7
Q

What is the difference between mono/amphi/lopho/peritrichous flagellum?

A
  • monotrichous - 1 flagellum at 1 end
  • amphitrichous - 1 flagellum at either end
  • lophotrichous - bundle of flagella at one end
  • peritrichous - flagella all around the cell
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8
Q

What is the importance of endospores?

A

Metabolically inactive, resistant form of bacteria which surivives the enviroment

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9
Q

What are the needs of simple and complex (fastidious) bacterium?

A

Simple - glucose, phosphate, sulphate, ammonium ions
Complex - growth factors- aa, fa, vitamins, nucleotides

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10
Q

What are the optimal temp and pH for bacterium?

A

35-37 degrees- mammals
25 degrees- cold blooded hosts
40 degrees- birds
pH neutral or slightly alkaline

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11
Q

Whats is the difference between microaerophilc and factulatively anaerobic bacteria?

A

microaerophilc need a small concentration of oxygen to grow
factulatively anaerobic can grow with or with out oxygen

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12
Q

What causes Microaerophiilic bacteria to die due to too much oxygen?

A
  • metabolism releases hydrogen peroxide or superoxide radical
  • micro doesnt have much catalse or superoxide dimutase so the cell is bleached and dies
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13
Q

What is Permease?

A

channel proteins carrying certain substrates only

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14
Q

How is iron uptake done?

A

done by siderophores by removing iron binding proteins from blood cells

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15
Q

What are the types of bacterial fermentation and what are the importance of them?

A

-Lactic acid, Ethanol, butyric acid, mixed acid, butanediol, propanoic acid
-they have different smells and can be used to determine the type of bacteria

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16
Q

What are haemolytic bacteria?

A

Bacteria that destroy blood cells

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17
Q

What are the types of medium used to grow bacteria?

A
  • Nutritionally simple e.g. agar
  • Enriched such as blood agar
  • Selective media that cause inhibition of other bacteria & specific enrichment of wanted bacteria
  • Differential media that cause visual differentiation of bacterial colonies
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18
Q

Whats the difference between exogenous and endogenous?

A

Exo are from enviroment or other hosts
endo are from animals own commensal flora

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19
Q

What are Faculative pathogens?

A

harmless saprophytes but do have the facility to be pathogenic given the host condition have altered

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20
Q

How does E.coli and Staph. aureus become pathogenic?

A

if they enter the an area where they are not found, they can cause peritonitis, abscesses or speticaemia depending on where it is now found

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21
Q

What factors can cause facultative bacteria to become pathogenic?

A

new body site
altered body site (temp, pH or flora)
reduced defences

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22
Q

What can alter commensal flora?

A

antibiotics

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23
Q

What reduces defences to bacteria?

A
  • Extremes of age, malnutrition, immunosuppressive drugs or primary infection
  • Stress → transport, crowding, temp extremes, wounding, fatigue, feed changes
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24
Q

How does stress in cattle transport cause pneumonia?

A

Shipping fever → Transporting cattle → stress and cortisol release → reduced immune and primary respiratory viral (parainfluenza virus) → damaged alveolar macrophages → susceptibility to secondary bacterial (Mannheimia haemolytica) → pneumonia

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25
Q

What is pathogenicity?

A

ability of a bacterial species to cause disease

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26
Q

What is Virulence?

A

degree of pathogenicity with a particular bacterial

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27
Q

What are Virulence determinants?

A

structural features or biochemical overcome and evade host defences

28
Q

How do bacteria invade hosts?

A
  • multiply at skin/mucous membrane surface
  • Superficial invasion of skin/mucous membrane
  • Deeper invasion of body via blood/lymph systems
29
Q

How do bacteria evade the complement system?

A
  • avoid triggering - hide antigens under bacterial (capsule) or host material (fibrin)
  • Trigger cascade but avoid effect - Steric hinderance of formation of the MAC
  • Mutate and avoid antibody recognition
  • Prevent compliment activation
30
Q

How can bacteria avoid triggering the complement cascade

A
  • No receptor on bacterium for antibody - lower recognition
  • Capsule and LPS
  • Staphylococcus converts fibrinogen to fibrin using coagulase so it can hide and look like host (some species though)
31
Q

What does lots of fimbrae do in immune evasion?

A
  • Hold on tight to epithelium
  • Prevent uptake by macrophages and digestion
32
Q

What can bacteria do to avoid the non-specific immune system?

A

Produce chemicals to
- Repels phagocytes or inhibit chemotaxis
- Prevent phagocyte activity (leukostains)
- Kills phagocytes (leukocidins)

33
Q

What host factors control bacterium growth?

A
  • Restriction of iron
  • Bile in the intestine
  • Oxygenation and the lysosome
34
Q

How can bacteria evade the host immune system?

A
  • Use fibrin to look like the host
  • Need to mutate to not look like themselves
  • Invade the host to hide
  • Need to rely on those around them
35
Q

What happens if bacteria and Protazoa mix in the enviroment?

A

Protozoa can graze on bacteria and then bacteria if they survive can hide in the protozoa

36
Q

What is biofilm?

A

collection of microbes living on a surface in a complex community

37
Q

How is biofilm formed?

A
  1. bacteria attach to surface using fimbrae
  2. make polysaccharide capsule material
  3. bacteria and yeast come and join in
  4. big 3D structure formed. Anaerobic on inside and aerobic on outside
  5. bacteria can detach or large bits of biofilm can detach
38
Q

How do bacterial heart blockages form?

A

-staphylococcus/streptococcus can grow
-attach, grow and block
-shedding of streamers from mature biofilm causes distal blockages
-caused by dental plaque, oral surgery, bacteraemia and transient bacteraemia

39
Q

What are biofilms resistant to?

A

Disinfectants
antibiotics

40
Q

How can a bacterium protect a whole biofilm?

A

Beta lactamase production by some bacteria protect all

41
Q

How can you prevent biofilm formation?

A

-stop bacteria getting into blood
-change catheters

42
Q

How does bacteria cross the skin barrier?

A
  • Active penetration: Digest their way in
  • Passive penetration via wounds, hair follicles & sweat glands
  • Via arthropod vectors such blood sucking sucking
43
Q

How do bacteria cross mucous membranes?

A
  • Produce mucinase to digest mucin
  • Move via chemotaxis (move towards a concentration gradient of nutrients)
  • Take up iron via iron-binding siderophores which is important in growth
  • Use adhesins to stick to the surface
44
Q

What are the specific and non-specific adhesins?

A

non-specific - Hydrophilic/hydrophobic adhesins
Specific - Lipoteichoic acid, capsular material, fimbrial proteins

45
Q

What do bacteria in the respiratory tract produce?

A

Bacteria produce ciliostatic & ciliotoxic products

46
Q

What do bacteria in the urinary tract produce?

A

Urease production

47
Q

What is the sneaky bacteria invasion?

A
  • Bacteria attach to the target cell via adhesins
  • Stimulate endocytosis of the cell causing it to take up bacteria
  • Leads to intracellular survival of bacteria
  • Bacteria survive in a phospholipid bilayer surrounded endosome within the host cell
  • They are protected from the immune system and take up nutrients
48
Q

How can bacteria be taken up by epithelium from circulation?

A
  • Bacteria can be taken up from the epithelium and then multiply in the epithelial cell before exiting at the bottom of the epithelial cell into the body
  • Or bacteria can be taken up across Peyer’s patches within M-cells that would normally sample antigen. Once inside they get taken up by macrophages which provide a way bacteria can be carried around the body
49
Q

What allows bacteria to invade deeper?

A

transcytosis

50
Q

What is bacterial chromasomal DNA?

A
  • Principal DNA - encodes all key functions
  • Nuclear region
  • 1 copy of either circular or double stranded supercoiled chromosome
51
Q

Whats the importance of non-chromasomal DNA?

A

mate by giving non chromosomal DNA portions

52
Q

What are plasmids

A
  • Extra chromasomal circular DNA
  • Idependeent in replication
  • usually codes for auxillary genes but addiction mechanisms exist - dies if loses plasmid
  • there more than 1 type per cell
  • Each plasmid has copys
53
Q

What are the 5 types of plasmids?

A

R-resistance; V-Virulence; Col-colicin; F-fertility;D-degradative

54
Q

What are the structure of transposons?

A
  • Have inverted repeats at the end of the molecule which bind to bits of bacterial DNA
  • Encode transposase which is an enzyme to cut themselves out of bacterial DNA once they’ve replicated
55
Q

How does transposon intergration occur?

A

Transposons incise their inverted repeats which then is incised into the host chromosome or plasmid. Different transposons recognise different base sequences because of their different inverted repeats

56
Q

How does bacterial genetic variation lead to evolution?

A
  • Can lead to changes in virulence
  • Can confer resistance to host defences & treatments
57
Q

What are the 5 main ways of variation in resident genome?

A
  • Lead to multiple similar genes
  • Via silent gene fragments
  • Gene/promoter inversion
  • Transposon activity
  • Spontaneous mutations
58
Q

What are the 3 methods of recombination in bacteria?

A

Transformation, generalised & specialised transduction & conjugation

59
Q

What happens during transformation?

A
  • Cell death & lysis
  • This releases plasmids & chromosomal fragments
  • These are taken up by other bacteria
  • Plasmids act alone
  • Chromosomal fragments integrate into the chromosome
60
Q

What are requirements of bacterial transformation?

A
  • No expansion of the population with a particular gene the gene just moves host
  • Extracellular DNA is subject to degradation, so bacteria need to be competent to take DNA up
  • Gene transfer involves low numbers and is random
  • Intracellular DNA is subject to degradation by bacteria
  • Homology is required for chromosomal DNA to loop in
61
Q

What is phage conversion?

A

A minority of bacterial virulence determinants e.g. some toxins are surface antigens are usually encoded by bacteriophage DNA not host DNA. The phenotypic expression of such phage products during lysogeny is phage conversion

62
Q

What are bacteriophages?

A

viruses that infect bacteria

63
Q

What is the lytic life cycle of bacteriophage?

A

phage DNA enters cell → host mechanism shut down under phage control → phage replication and capsid production → progeny phage assembled → host cell lyses and new phage particles releasaed

64
Q

What is the lysogenic life cycle of bacteriophage?

A

phage DNA enters host → site specific integration pf phage DNA into host chromosome or a plasmid → silent prophage replicates with host DNA → stimulus prophage excision occurs dollowed by phage entering lytic life cycle

65
Q

What is transduction and the difference between specialised and general?

A

packaging error - phage picks up host DNA (chromasome fragment/plasmid) by mistake
- phage DNA packaged - specialised transduction
- Host DNA only - generalised transduction

AD2 (39 decks)

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