Micro Unit 1: Bacterial Structure and Function 1

Question 1

Defining structural characteristics of bacteria

Answer 1

• No introns
• single circular chromosome
• Nucleoid: like a eukaryotic nucleus, concentrates the genome in one intracellular position. however, NO membrane.
• 70S ribosome
• peptidoglycan cell wall
• binary fission

Question 2

4 major shapes

Answer 2

1. cocci (staph, strep)
2. rods (e.coli, pseudomonas)
3. vibrios (v. cholerae)
4. spirochetes (Neisseria)

Question 3

Gram staining procedure

Answer 3

1. fix bacteria to slide w/ heat
2. stain w/ crystal violet
3. iodine treatment (gram + turns permanently purple)
4. decolorize w/ alcohol (gram - color goes away)
5. counterstain (safrinin restains gram -)

Question 4

Difference between gram + and gram - cell walls

Answer 4

Gram + cell wall has 3 layers of peptidoglycan and NO exterior membrane

Gram - has 1 layer of peptidoglycan and HAS an exterior membrane

Question 5

What is LPS?

Answer 5

Lipopolysaccharide, an endotoxin

• component of gram - cell walls
• can cause septic shock DURING sepsis or AFTER abx treatment when LPS released from dead bacteria

Question 6

Teichoic acids

Answer 6

Closest gram + equivalent to LPS but much less likely to cause sepsis

Question 7

Glycocalyx

Answer 7

2 types: slime layer and capsule

Question 8

Slime layer

Answer 8

loose coating of polysaccharide helps bacteria attach to host cells and form biofilms

Question 9

Capsule

Answer 9

Firm enclosure that helps with attachment, resists phagocytosis, potential vaccine target, virulence factor

Question 10

Pili/fimbrae

Answer 10

Used for attachment, often a virulence factor

• Gram + pili are covalently linked pilin subunits
• Gram - pili have many types, have many molecules, and have evolved into propulsion systems or secretion systems that are virulence factors in their own right