Bacteriology

Question 1

Sterols are found in the cell membranes of eukaryotes or prokaryotes?

Answer 1

Eukaryotes

Question 2

What is the difference between brightfield and darkfield microscopy?

Answer 2

1. In darkfield, a special condenser is used to prevent transmitted light from directly illuminating the specimen (only scattered light reaches the specimen, causing it to become bright against a dark background)2. Improved resolution in darkfield for visualization of thin bacteria

Question 3

What type of microscopy allows visualization of internal details?

Answer 3

Phase contrast

Question 4

What are characteristics of gram positive bacteria?

Answer 4

1. Thicker peptidoglycan layer2. Teichoic acid often present3. Sporulation in some strains4. Capsule sometimes present5. Sensitive to lysozyme6. More sensitive to penicillin7. Exotoxin production in some strains

Question 5

What are characteristics of gram negative bacteria?

Answer 5

1. Outer membrane2. Thinner peptidoglycan layer3. LPS present4. Capsule sometimes present5. Resistant to lysozyme6. More resistant to penicillin7. Exotoxin production in some strains

Question 6

What are characteristics of acid fast bacteria?

Answer 6

Peptidoglycan layer intertwined with covalently attached arabinogalactan polymer and surrounded by a waxlike lipid coat of mycolic acid

Question 7

What forms the rigid structure of the cell wall?

Answer 7

Peptidoglycan

Question 8

What are the steps of gram staining?

Answer 8

1. Crystal violet2. Crystal violet precipitated with iodine3. Decolorizer / wash4. Red safranin counter stain

Question 9

Where does stain get trapped in gram positive bacteria?

Answer 9

Peptidoglycan layer

Question 10

Where is LPS found?

Answer 10

Outer leaflet of gram negative outer membrane

Question 11

What are the three components of LPS?

Answer 11

1. Lipid A2. Core polysaccharide3. O antigen

Question 12

What is essential for LPS’s bacterial viability?

Answer 12

Lipid A

Question 13

What is essential for LPS’s endotoxin activity?

Answer 13

Lipid A

Question 14

What feature of LPS distinguishes serotypes of bacterial species?

Answer 14

O antigen

Question 15

What does LPS bind to?

Answer 15

CD14 and TLR4 on phagocytes and APCs

Question 16

What are pili?

Answer 16

1. Tube like structure made of proteins 2. Hollow core 3. On surface of gram negative and gram positive

Question 17

What test is used to identify bacterial capsules?

Answer 17

Quellung

Question 18

Do gram negative bacteria form endospores?

Answer 18

No

Question 19

Do gram positive bacteria form endospores?

Answer 19

Some can

Question 20

What are characteristics of endospores?

Answer 20

1. Complete copy of chromosome2. Bare minimum of essential ribosomes and proteins3. High concentration of calcium bound to dipicolinic acid4. Has inner membrane, two peptidoglycan layers and an outer keratin like protein coat