Lecture 4 Basic Microbial Morphology

Question 1

Name the two types of prokaryotic cells

Answer 1

Bacteria
Archaea

Question 2

Name the most important differential staining method in microbiology

Answer 2

The Gram Stain

Question 3

Example of gram postive bacteria

Answer 3

Staphylococci

Question 4

Example of gram negative bacteria

Answer 4

Escherichia coli

Question 5

Explain the gram stain mechanism

Answer 5

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

Question 6

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

Answer 6

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

Question 7

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

Answer 7

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

Question 8

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

Answer 8

Mycobacteria

Question 9

Why don’t Mycobacteria stain using the gram stain method

Answer 9

have a high wax content in their cell envelope

Question 10

Name the method used to stain mycobacteria

Answer 10

Ziehl-Nielson stain

Question 11

Name the smallest known bacteria

Answer 11

Mycoplasmas

Question 12

Why can’t mycoplasma use the gram stain method

Answer 12

They have no cell wall to stain

Question 13

Name the types of bacterial shapes

Answer 13

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

Question 14

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

Answer 14

Bacterial chromosome

Question 15

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

Answer 15

Plasmids

Question 16

Name the structure that surrounds the cytoplasm

Answer 16

Cytoplasmic membrane

Question 17

Name the rigid layer surrounding the cytoplasmic membrane

Answer 17

Cell wall

Question 18

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

Answer 18

Outer membrane

Question 19

What is the cytoplasmic membrane primarily composed of

Answer 19

Lipids
Phospholipids

Question 20

Does cytoplasmic membrane have an osmotic barrier

Answer 20

Yes , only molecules smaller than glycerol diffuse into the cytoplasm

Question 21

Where is the site of energy production oxidative phosphorylation

Answer 21

Cytoplasmic membrane

Question 22

How are important molecules transported in cytoplasmic membrane

Answer 22

Via Permeases

Question 23

Name the types of membrane transport in cytoplasmic membrane

Answer 23

Facilitated diffusion (passive)
Active transport

Question 24

Where does synthesis of new cell wall occur in bacteria cell

Answer 24

Cytoplasmic membrane

Question 25

Name the structure that anchor the chromosome of bacteria cell

Answer 25

Cytoplasmic membrane

Question 26

What is bacteria cell wall composed of

Answer 26

Peptidoglycan

Question 27

What is Archaea cell wall composed of

Answer 27

Lacks peptidoglycan but composed of other polysaccharides or proteins

Question 28

Function of cell wall in bacterial cells

Answer 28

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

Question 29

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

Answer 29

Peptidoglycan

Question 30

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

Answer 30

90% of cell envelope

Question 31

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

Answer 31

2-20% of cell envelope material

Question 32

Name the antibiotic that disrupts Peptidoglycan synthesis

Answer 32

Penicillin

Question 33

What does NAG stand for in Peptidoglycan

Answer 33

N-acetylglucosamine

Question 34

What does NAM stand for in Peptidoglycan

Answer 34

N-acetylmuramic acid

Question 35

Which bonds connects NAM and NAG (G-M)

Answer 35

β(1,4) glycosidic bond

Question 36

Describe cell wall of Archaea

Answer 36

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

Question 37

Describe gram negative cell envelope outer membrane

Answer 37

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

Question 38

What is gram negative cell envelope outer membrane resistant to

Answer 38

Phagocytosis

Question 39

Name the structure that extend from the cell surface

Answer 39

Flagella Pili

Question 40

Function of flagellae

Answer 40

They rotate and are required for motility (chemotaxis)

Question 41

What do bacteria swim towards

Answer 41

Chemoattractants

Question 42

What do bacteria swim away from

Answer 42

Chemorepellents

Question 43

What structure do bacteria use to swim

Answer 43

Flagella

Question 44

what is conjugative pili used for in bacteria cell

Answer 44

Plasmid transfer

Question 45

what is common pili used for in bacteria cell

Answer 45

Adherence