Bacterial Properties Flashcards

1
Q

What is the difference between Gram-negative and Gram-positive bacteria?

A

Gram-negative bacteria have a thin peptidoglycan layer with two membranes (cytoplasmic and outer membranes)
Gram-positive bacteria have a thick peptidoglycan layer, which retains the dye well. It only has one membrane

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2
Q

Give examples of some Gram-negative pathogenic bacteria and the diseases they cause.

A
E. coli – diarrhoea, dysentery, kidney failure
Salmonella  - food poisoning, typhoid
Shigella – dysentery
Neisseria – meningitis + gonorrhoea
Vibrio cholerae - cholera
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3
Q

What feature is found only on Gram-negative cell walls?

A

Lipopolysaccharide

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4
Q

Give examples of some Gram-positive pathogenic bacteria and the diseases they cause.

A

Staphylococcus aureus – skin infections, endocarditis, bacteraemia, pneumonia
Streptococcus pneumoniae – pneumonia, meningitis, otitis media
Streptococcus pyogenes – tonsillitis, necrotising fasciitis, scarlet fever

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5
Q

Give examples of some Mycobaceria and the diseases they cause

A

Mycobacterium tuberculosis – TB

Mycobacterius leprae - leprosy

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6
Q

What is another way of classifying bacteria?

A

Intracellular and Extracellular pathogens

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7
Q

Give examples of some extracellular pathogens.

A

Staphylococcus
Streptococcus
Neisseria
Yersinia

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8
Q

What are the three methods by which bacteria survive in the host cell?

A

Escape
Preventing fusion with lysosome
Surviving in the phagolysosome

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9
Q

Give examples of bacteria that survive using each of the above methods.

A

Escape – Listeria, Shigella
Prevent fusion of lysosome – Salmonella, Mycobacteria, Chlamydia
Survive in phagolysosome - Coxiella

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10
Q

Motility and Invasion require which two multi-protein machines?

A

Flagella

Type III Secretion system

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11
Q

Describe the role of the type III secretion system.

A

A protein machine assembles which provides a channel through which virulence proteins can be injected into the host cell
The virulence proteins then stimulate actin polymerisation and membrane ruffling which allows bacterial internalisation
Gram-positive bacteria don’t have the type III secretion system

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12
Q

Describe another way in which actin is manipulated by bacteria.

A

Bacteria (such as listeria and shigella) can polymerise actin at one pole of the bacterium forming comet tails
This polymerisation propels the bacterium through the cytoplasm

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13
Q

What are the three mechanisms of horizontal gene transmission?

A

Transformation, Transduction and Conjugation

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14
Q

Explain each of the three mechanisms of horizontal gene transmission.

A

Transformation – the uptake of naked DNA from the environment
Transduction – bacteriophages infect a bacterium and take up some of the bacterial DNA. The bacteriophage then carries the bacterial DNA to another bacterium.
Conjugation – transfer of genetic material in the form of a plasmid via a conjugation tube

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15
Q

What is a Pathogenicity Island?

A

Horizontally acquired genes that contribute to the virulence

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