Bacteria

Question 1

What are the 4 phyla of bacteria ?

Answer 1

1. proteobacteria
2. actinobacteria
3. firmicutes
4. bacteriodetes

Question 2

Describe prokaryotic DNA

Answer 2

• Typically a single circular chromosome that aggregates to form the nucleoid region
• may also have plasmids
• small & compact

Question 3

Describe plasmids

Answer 3

circular/linear double-stranded DNA that replicate separately from chromosome

Question 4

What are the 3 major cell morphologies ?

Answer 4

• coccus
• bacillus
• spirillum

Question 5

What shape does coccus describe ?

Answer 5

spherical

Question 6

What shape does bacillus describe ?

Answer 6

rod/cylindrical

Question 7

What shape does spirillum describe ?

Answer 7

spiral

Question 8

What are some unusual bacteria shapes?

Answer 8

• spirochetes
• appendages bacteria
• filamentous bacteria

Question 9

Describe the peptidoglycan cell wall

Answer 9

• rigid layer that provides strength to the cell wall
• polysaccharide
• can be gram-positive or negative –> effects cross-linkage

Question 10

What is the peptidoglycan cell wall comprised of ?

Answer 10

• amino acids
• lysine/diaminopimelic acid
• N-acetlyglucosamine
• N-acetylmuramic acid

Question 11

Describe the structure of a gram-positive peptidoglycan cell wall

Answer 11

• upto 90% peptidoglycan
• common to have teichoic acids covalently bound peptidogylcan
• lioteichoic acids
• divalent metal ions are bound prior to transport

Question 12

What are lipoteichoic acids ?

Answer 12

teichoic acids covalently bound to membrane lipids

Question 13

Describe the LPS - Outer membrane of prokaryotes

Answer 13

• lipopolysaccharide layer makes up most of the cell wall
• barrier against antibiotics & harmful agents
• LPS replaces most of the phospholipids in the outer half of the outer membrane

Question 14

What does the LPS/lipopolysaccharide consist of ?

Answer 14

• core polysaccharide
• O-polysacchairde
• lipid A

Question 15

What is endotoxin ?

Answer 15

Lipid A –> the toxic part of the LPS

Question 16

What are differential stains?

Answer 16

different kinds of cells are different colours

Question 17

What are a good example of differential staining ?

Answer 17

• Gram stains
• positive = purple/violet
• negative = pink

Question 18

Describe the structure of capsules & slime layers

Answer 18

• polysaccharide layers
• assists in the attachment to surfaces
• protects against phagocytosis
• resists desiccation

Question 19

Describe fimbriae

Answer 19

• filamentous protein structures - 2-10nm wide
• enables organisms to stick to surfaces or form pellicles

Question 20

What are pellicles ?

Answer 20

thin sheets of cells on a liquid surface

Question 21

Describe Pili

Answer 21

• typically longer and fewer per cell than fimbriae
• conjugative/sex pili facilitate genetic exchange between cells
• Type IV pili adhere to host tissues & support twitching motility

Question 22

Describe Endospores

Answer 22

• highly differentiated cells resistant to hear, harsh chemicals and radiation
• ‘dormant’ stage of bacterial life cycle
• ideal for dispersal via wind, water or animal gut

Question 23

When are endospores formed ?

Answer 23

during endosporulation or sporulation

Question 24

Where are endospores present ?

Answer 24

• only in some gram-positive bacteria

Question 25

Describe the formation of endospores

Answer 25

• vegetative cell converted to non-growing, heat-resistant, light refractive structure
• only occurs when growth ceases due to lack of essential nutrients such as nitrogen or carbon

Question 26

Describe the function of flagella

Answer 26

• structure that assists in swimming in bacteria

Question 27

Describe Flagella & Flagellation

Answer 27

• long, thin appendages - 15-20nm wide
• helical in shape with a filament made of flagellin
• increase/decrease rotational speed relative to strength of proton motive force

Question 28

What are the different arrangements of flagella ?

Answer 28

• polar
• lophotrichous
• amphitrichous
• peritrichous