3.4 Microbiology Flashcards

1
Q

What are the 4 classification methods for bacteria?

A

Size and shape, Gram stain, Metabolic reaction (mode of nutrition), Antigenic and genetic features.

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2
Q

What are 2 mode of nutrition for bacteria?

A

Heterotopic and autotrophic

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3
Q

What is the correct name for sphere shaped bacteria?

A

Cocci

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4
Q

What is the correct name for rod shaped bacteria?

A

Bacilli

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5
Q

What is the correct name for spiral shaped bacteria?

A

Spirilum

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6
Q

What colour is a positive gram stain?

A

Violet

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7
Q

What colour is a negative gram stain?

A

Red

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8
Q

Why does gram positive bacteria go purple?

A

They have thicker peptidoglycan layers and no outer lipopolysaccharide layer allowing the violet complex to be retained

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9
Q

Why does gram negative bacteria go red?

A

They have a thinner peptidoglycan layer and an outer lipopolysaccharide layer. They do not retain the violet complex but do retain the red counterstain

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10
Q

How thick is the cell wall of gram negative bacteria?

A

8-12 nm

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11
Q

How thick is the cell wall of gram positive bacteria?

A

20-30 nm

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12
Q

Which gram stain is resistant to penicillin and lysozyme?

A

Gram negative bacteria

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13
Q

What 5 conditions are necessary for bacteria growth in a lab?

A

Suitable temperature and pH, nutrition, water, optimal oxygen conditions met

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14
Q

What is an obligate aerobe?

A

Bacteria that grows in the presence of oxygen

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15
Q

What is an obligate anaerobe?

A

Bacteria that grows in the absence of oxygen

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16
Q

What is a facultative anaerobe?

A

Bacteria that thrives with oxygen but can grow in its absence

17
Q

What occurs in the Lag phase of bacterial growth?

A

acclimatisation-enzyme synthesis etc

18
Q

What occurs in the Log phase of bacterial growth?

A

Population doubles every generation with plentiful recourses and ideal reproduction conditions

19
Q

What occurs in the stationary phase of bacterial growth?

A

resources are depleting and waste products build becoming toxic

20
Q

What occurs in the death phase of bacterial growth?

A

toxins kill living cells and resources can no longer support life

21
Q

What is a viable count?

A

Total living or actively growing cells

22
Q

What is assumed in a viable count?

A

Each colony arose from a single bacterium- may not be true due to clumping

23
Q

Why are aseptic techniques used?

A

Avoid culture contamination and avoid personelle contamintation

24
Q

Give 2 main ways to sterilise equipment?

A

Heat and radiation

25
Q

What is serial dilution?

A

Diluting a sample to make bacterium countable