L3_ Bacterial Structure and Function 1

Question 1

How do bacteria reproduce?

Answer 1

Binary Fission

Question 2

Describe Bacterial genome

Answer 2

DNA, No introns, Polycistronic, singular circular chromosome, Nucleoid (no membrane)

Question 3

What kind of ribosomes do bacteria have?

Answer 3

70S

Question 4

What are bacterial cell walls made of?

Answer 4

peptidoglycan

Question 5

How big are bacteria? Compared to viruses and to eukaryotic cells

Answer 5

0.5-5um. 10-100x smaller than eukaryotic, 500-1000x larger than viruses

Question 6

Are bacteria visible by light microscope with contrast and staining?

Answer 6

Yes

Question 7

What are the three major shapes of bacteria?

Answer 7

Cocci (round), Rods (oval), Spirochetes (corkscrew)

Question 8

What are 3 characteristic clumping patterns of Cocci?

Answer 8

Clumps (staph), Chains (strep), Diplococci (Neisseria)

Question 9

Name the Five steps of Gram Staining

Answer 9

1 Fix the bacteria to microscope slide with heat
2 Stain with crystal violet (all turn purple)
3 Iodine Treatment (Gram + permanently purple)
4 Decolorize with Alcohol (Removes CV form Gram -)
5 Couterstain (Safarin re-stains Gram - light pink)

Question 10

Describe the membrane and cell wall structure of GRAM (-) bacteria

Answer 10

Thin wall with 1 layer of peptidoglycan. Stains pink in GRAM staining. Interior membrane plus exterior membrane with LPS(septic Shock) and Porins which allow for selective permeability.

Question 11

Describe the membrane and cell wall structure of GRAM (+) bacteria.

Answer 11

Thick wall with 3 layers of peptidoglycan. Stains purple in GRAM staining. Only interior membrane. Teichoic Acid are equivalent of LPS but much less frequently cause shock.

Question 12

What purpose does the cell wall serve for bacteria.

Answer 12

Gives rigidity and helps resist osmotic forces.

Question 13

What are some vulnerabilities of cell walls?

Answer 13

They are target by host cell and many antibiotics. Antibiotics will prevent synthesis, lysozyme will cleave wall.

Question 14

Can you vaccinate against LPS?

Answer 14

NO! it is immunogenic and vaccinating against it would only increase it virulence

Question 15

What are the two main components of the glycocalyx layer? What are these layers rich in?

Answer 15

Slime Layer and Capsule. Carbohydrate rich

Question 16

What does the slime layer do?

Answer 16

Attachment

Formation of biofilms (antibiotic resistance)

Question 17

What does the Capsule do for bacteria?

Answer 17

Protective,
Antiphagocytic
serological testing
vaccine target
attachment

Question 18

What are the purpose of pili/fimbrae and how do they differ between GRAM neg and pos bacteria?

Answer 18

Used for attachment and often a virulence factor. Gram pos were only recently discovered and are simple repeating subunits. Gram neg come in many types and are complex, some have evolved into propulsion systems or secretion molecules that are virulence factors in their own right.

Question 19

What causes gram - to resist CV stain?

Answer 19

Outer membrane

Question 20

How do Acid Fast bacteria stain and why?

Answer 20

Mycolic acid layer resists both CV and counterstain…need to use acid fast procedure

Question 21

Is LPS and endo or exotoxin?

Answer 21

Endotoxin

Question 22

What type of GRAM neg pili are used for attachment? propulsion? secretion?

Answer 22

Type1 for attachment, type 4 for propulsion, type 3 and 4 for secretion.

Question 23

Give and example of two bacilli and two spirochetes

Answer 23

Bacillus and vibrio are bacilli, borrelia and treponema are spirochetes