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microbiology > Lecture 4 Basic Microbial Morphology > Flashcards

Lecture 4 Basic Microbial Morphology Flashcards

1
Q

Name the two types of prokaryotic cells

A

Bacteria
Archaea

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2
Q

Name the most important differential staining method in microbiology

A

The Gram Stain

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3
Q

Example of gram postive bacteria

A

Staphylococci

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4
Q

Example of gram negative bacteria

A

Escherichia coli

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5
Q

Explain the gram stain mechanism

A

Differential lipid content of G+ and G- cell envelopes
Crystal violet-iodine complex forms within the cells (Blue colour)

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6
Q

What effect does alcohol treatment for gram stain method have on gram negative cell envelope

A

G- cell envelope has a high lipid content which is extracted by alcohol to permeabilise the memberane

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7
Q

What effect does alcohol treatment for gram stain method have on gram positive cell envelope

A

G+ cell envelope has low lipid
content and is dehydrated by
alcohol - making it impermeable

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8
Q

Name the bacteria that doesn’t stain using the gram stain method

A

Mycobacteria

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9
Q

Why don’t Mycobacteria stain using the gram stain method

A

have a high wax content in their cell envelope

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10
Q

Name the method used to stain mycobacteria

A

Ziehl-Nielson stain

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11
Q

Name the smallest known bacteria

A

Mycoplasmas

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12
Q

Why can’t mycoplasma use the gram stain method

A

They have no cell wall to stain

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13
Q

Name the types of bacterial shapes

A

Cocci(Spherical)
Bacilli(Rod shaped)
Curved or spiral shaped

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14
Q

Name the structure in a bacterial cell containing the bacterial genetic information

A

Bacterial chromosome

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15
Q

Other than bacterial genetic information what else is found in the chromosome

A

Plasmids

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16
Q

Name the structure that surrounds the cytoplasm

A

Cytoplasmic membrane

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17
Q

Name the rigid layer surrounding the cytoplasmic membrane

A

Cell wall

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18
Q

Name the structure that cover the cell wall and acts as a molecular sieve for gram negative bacteria

A

Outer membrane

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19
Q

What is the cytoplasmic membrane primarily composed of

A

Lipids
Phospholipids

20
Q

Does cytoplasmic membrane have an osmotic barrier

A

Yes , only molecules smaller than glycerol diffuse into the cytoplasm

21
Q

Where is the site of energy production oxidative phosphorylation

A

Cytoplasmic membrane

22
Q

How are important molecules transported in cytoplasmic membrane

A

Via Permeases

23
Q

Name the types of membrane transport in cytoplasmic membrane

A

Facilitated diffusion (passive)
Active transport

24
Q

Where does synthesis of new cell wall occur in bacteria cell

A

Cytoplasmic membrane

25
Q

Name the structure that anchor the chromosome of bacteria cell

A

Cytoplasmic membrane

26
Q

What is bacteria cell wall composed of

A

Peptidoglycan

27
Q

What is Archaea cell wall composed of

A

Lacks peptidoglycan but composed of other polysaccharides or proteins

28
Q

Function of cell wall in bacterial cells

A

Allows cell to withstand turgor pressure and give cell shape and rigidity

from high concentration of dissolved solutes that generate a high pressure within cell caused by cytoplasm pressing again cell envelope

29
Q

Name the principle component of bacterial cell wall that prevent osmotic lysis

A

Peptidoglycan

30
Q

What percentage of cell envelope material is made up of Peptidoglycan layers in gram positive

A

90% of cell envelope

31
Q

What percentage of cell envelope material is made up of Peptidoglycan layers

A

2-20% of cell envelope material

32
Q

Name the antibiotic that disrupts Peptidoglycan synthesis

A

Penicillin

33
Q

What does NAG stand for in Peptidoglycan

A

N-acetylglucosamine

34
Q

What does NAM stand for in Peptidoglycan

A

N-acetylmuramic acid

35
Q

Which bonds connects NAM and NAG (G-M)

A

β(1,4) glycosidic bond

36
Q

Describe cell wall of Archaea

A

No peptidoglycan
S-layer composed of a ordered layer of protein or glycoprotein Eg(thermophiles, halophiles, methanogens)
Few Archaea contain pseudopeptidoglycan
Repeated sugar units, however, ab1,3-linked) Example: Methanogens
Polysaccharides

37
Q

Describe gram negative cell envelope outer membrane

A

Phospholipid-Lipopolysaccharide (LPS)bilayer (extra lipid layer - mechanism of gram stain)
Bacterial cell adhesion
Molecular sieve - access of some molecules to cell wall and cytoplasmic membrane

38
Q

What is gram negative cell envelope outer membrane resistant to

A

Phagocytosis

39
Q

Name the structure that extend from the cell surface

A

Flagella
Pili

40
Q

Function of flagellae

A

They rotate and are required for motility (chemotaxis)

41
Q

What do bacteria swim towards

A

Chemoattractants

42
Q

What do bacteria swim away from

A

Chemorepellents

43
Q

What structure do bacteria use to swim

A

Flagella

44
Q

what is conjugative pili used for in bacteria cell

A

Plasmid transfer

45
Q

what is common pili used for in bacteria cell

A

Adherence

microbiology (18 decks)

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