Microbiology Flashcards

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1
Q

What are the ways we can classify bacteria?

A

Size, shape, staining characteristics, antigenic features

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2
Q

What does bacillus mean in terms of bacteria shape?

A

Rod shaped

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3
Q

What does coccus mean in terms of the shape of bacteria?

A

Spherical

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4
Q

What does spiral mean in terms of shape of bacteria?

A

Cork screw

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5
Q

Why do bacteria stain different colours?

A

Due to the different chemical composition of cell wall

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6
Q

What colour do gram positive turn when gram stained? Why?

A

Purple - thick layer of peptidoglycan

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7
Q

What is the first step of gram staining?

A

Crystal violet binds to the peptidoglycan layer

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8
Q

What is the 2nd step of gram staining?

A

Iodine complex binds crystal violet to peptidoglycan more strongly

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9
Q

What is the 3rd step of gram staining?

A

Gram negative lose their outer lipopolysaccharide layer and crystal violet and iodine complex is washed away

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10
Q

What’s the 4th step of gram staining?

A

Safranin (counterstain) turns gram negative red

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11
Q

What are some nutrients that are supplied in media that re required?

A

Carbon compounds, glucose, nitrogen, growth factors (minerals and vitamins)

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12
Q

What’s the definition of a obligate aerobe?

A

A microorganism/bacteria that grow in they presence of oxygen

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13
Q

What is the definition of an obligate anaerobe?

A

Microorganism/bacteria that grow in the absence of oxygen

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14
Q

What is the definition of a facultative anaerobe?

A

A microorganism/bacteria that can grow with or without oxygen

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15
Q

What is aseptic technique used to prevent?

A

Contamination of environment by microbes
Contamination of the culture by unwanted microbes from the environment

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16
Q

How do you prevent contamination to apparatus?

A

Sterile all apparatus, sterile work surfaces, handle carefully

17
Q

What is an autoclave?

A

Sealed container where glass and metal equipment is sterile using heat

18
Q

What temperature does the autoclave reach? Why? How long?

A

121 degrees, that’s when steam is produced, 15 minutes

19
Q

Why is the autoclave in pressure?

A

Pressure helps the stream reach the equipment

20
Q

When securing the Petri dish with tape, why not put it all the way around?

A

Anaerobe conditions could be created and the bacteria may be obligate aerobe

21
Q

What is a viable count?

A

Living cells only (plating and counting colonies)

22
Q

What is a total count?

A

Living and dead cells

23
Q

Why do we serial dilute?

A

To produce clear and distinct colonies that aren’t clumped