Bacterial Structure

Question 1

What are the major structural components of bacterial cell wall

Answer 1

1. Flagellum
2. Plasmid
3. Chromosomal plasmid
4. ribosome

Question 2

Steps of gram staining

Answer 2

1. Primary stain (crystal violet)
2. Fixer (iodine)
3. Decolorisation (alcohol/acetone)
4. Counterstain (sarfranin/carbol fuchsin)

Question 3

Define peptidoglycan layer of gram + bacteria

Answer 3

thick layer; often described as dark or thick

Question 4

Define peptidoglycan layer of gram - bacteria

Answer 4

very thin layer

Question 5

Porins present in?

Answer 5

gram - bacteria

Question 6

What are the 3 structures present in lipopolysaccharides

Answer 6

O antigen side chain, core polysaccharide & lipid A (toxic)

Question 7

what colour is gram + bacteria

Answer 7

Purple

Question 8

what colour is gram - bacteria

Answer 8

Pink

Question 9

Describe flagellum

Answer 9

• long structure
• helps with bacterial motility
• helps with attachment or transfer of bacterial material

Question 10

Describe Plasmid

Answer 10

• small circular DNA molecule
• Physically separate from chromosomal DNA

Question 11

Periplasmic space in gram +

Answer 11

do not have a large periplasmic space

Question 12

Periplasmic space in gram -

Answer 12

have a very large periplasmic space inside the cell wall structure

Question 13

Who developed gram staining

Answer 13

Developed by Hans Christian Gram

Question 14

Role of gram staining

Answer 14

Simple yet informative method used to distinguish bacteria based on their cell wall structure

Question 15

What are the surface structures of bacteria

Answer 15

1. lipopolysaccharides
2. Capsule
3. Pilli & fimbriae
4. flagella
5. endospores

Question 16

Function of endospores

Answer 16

• way of bacteria to encapsulate the DNA
  
  • Contain DNA & thick cell layers

Question 17

Properties of endospores

Answer 17

• remain dormant
  extremely resistant to environmental stress

Question 18

Function of flagella

Answer 18

• Chemotaxis & motility
  
  • to sense the environment around it
• antigenic (H antigen); immune response

Question 19

Main purpose of sex pills

Answer 19

Conjugation

Question 20

Sex Pilus involves

Answer 20

a donor & a recipient

Question 21

Describe sex pilus function

Answer 21

allows the transfer of virulence genes (e.g. fimbriae) or antibiotic resistance genes or virulence enhancing pathogenicity enhancing all the factors that enable bacteria to cause disease could also be transferred through conjugation

Question 22

Role of sex pilus

Answer 22

the sex pilus enlarges find a donor & the recipient get to meet and most likely plasmids will be transferred from one bacteria to another

Question 23

Describe fimbriae

Answer 23

small, hair-like structures that enables the attachment of bacterial pathogens to mucosal surface

Question 24

Define conjugation

Answer 24

a transfer of genetic material from 1 bacteria to the other

Question 25

What is capsule composed of?

Answer 25

composed of polysaccharides or polypeptides

Question 26

What are the roles of capsule in bacteria

Answer 26

pathogenicity & cell protection can prevent the host’s immune system from recognising the bacteria

Question 27

What can capsule be involved in

Answer 27

involved in functional attachment where it allows bacteria to attach to various places

Question 28

Define endospore

Answer 28

thick encapsulated DNA

Question 29

Teichoic acid in gram + ?

Answer 29

Present

Question 30

Teichoic acid in gram -

Answer 30

Absent

Question 31

what does flagella require

Answer 31

requires energy & driven by a rotary engine at the anchoring point in the inner cell membrane

Question 32

Movement of flagella

Answer 32

rotate, do not flex, move counter clockwise direction

Question 33

Commensal pathogen

Answer 33

- Does not cause disease - part of normal flora (e.g. facial/nasal) - e.g. lactobacillus spp. commensal e. coli

Question 34

opportunistic pathogens

Answer 34

- most pathogens - occasionally cause disease - host immunocompromised > will lead to cause of disease - e.g. pathogenic e. coli, staphylococcus aureus

Question 35

Primary pathogens

Answer 35

- loose classification - highly virulent - e.g. mycobacterium tuberculosis

Question 36

describe shape of cocci

Answer 36

- round - grape like structure - Some of them in clusters/chains

Question 37

describe shape of bacilli

Answer 37

- Short rods - long rods - in chains