Micro Exam 1

Question 1

Classification

Answer 1

Based on taxonomic groups- morphological, biochemical, physiologic or genetic properties

Question 2

Nomenclature

Answer 2

Naming the organism based on it’s characteristics

Question 3

Identification

Answer 3

Use of classification scheme to isolate and identify organisms

Question 4

2 most common shapes

Answer 4

Cocci- round

Bacillus- rod shaped

Question 5

4 other common shapes

Answer 5

Coccobacillus- in between cocci and rod
Vibrio- comma
Spirochete- flexible corkscrew
Spirillum- rigid corkscrew

Question 6

Groupings on a single division plane

Answer 6

Diplo- pair

Strepto- chain

Question 7

Groupings on 2 or more planes

Answer 7

Staphylo- grapelike cluster
Tetras- packets of 4 cells
Sarcina- packets of 8 cells

Question 8

What bacteria have sterols and why don’t more?

Answer 8

Most bacteria do not contain sterols because the pathway that creates sterols requires O2- only some aerobic bacteria produce it.

Question 9

Cell membrane functions

Answer 9

• transport
• secretion
• house receptors and other proteins for chemotaxis and sensory transduction

Question 10

Cell wall description and functions (4 functions)

Answer 10

Semi-rigid structure outside the cell membrane

• maintain cell shape
• prevent osmotic lysis
• environmental protection
• anchor for external structures

Question 11

What is peptidoglyclan? What cell walls have it?

Answer 11

Peptidoglycan is found in virtually all cell walls.

-Repeating disaccharide (NAGs and NAMs) with tetrapeptides crosslinking the NAMs.

Question 12

What can interfere with the structure or synthesis of peptidoglycan?

Answer 12

• antimicrobial compounds

- lysozyme

Question 13

Describe how antimicrobial compounds damage cell walls?

Answer 13

Multiple different targets, but require actively growing cells that are synthesizing peptidoglycan

Question 14

How does lysozyme damage cell walls?

Answer 14

Weakens the integrity of the cell wall by degrading the glycan backbone of peptidoglycan

Question 15

Describe the cell wall of gram-negative bacteria.

Answer 15

Thin peptidoglycan layer- <10-15 sheets

Question 16

Describe the cell wall of gram-positive bacteria

Answer 16

Thick peptidoglycan layer- >20 sheets

Question 17

From outside in, the order of the layers in a gram-negative cell wall.

Answer 17

• Lipopolysaccharide- attached to the outer membrane
• outer membrane (with porins in the membrane, and lipoproteins into the periplasmic space)
• periplasmic space with the cell wall
• inner membrane

Question 18

What are the three components of the LPS layer?

Answer 18

• O antigen
• Core polysaccharide
• Lipid A

Question 19

What is the O antigen?

Answer 19

• outer portion of LPS
• linear repeating units of carbohydrates
• attachment site
• highly variable and immunogenic

Question 20

What is the core polysaccharide?

Answer 20

• branched polysaccharide

- connects lipid A to O antigen

Question 21

What is lipid A?

Answer 21

• lipid embedded in outer membrane
• has toxin activity
• responsible for bacterial sepsis

Question 22

How does LPS cause septic shock?

Answer 22

• LPS can activate complement through the alternative pathway
• binds receptors causing cytokines and pro-inflammatory mediators
• leading to septic shock

Question 23

Describe the outer membrane of Gram negative cell wall.

Answer 23

Has porins and lipoproteins

Question 24

What are porins?

Answer 24

trimeric non-specific protein channels that controls transport substances in/out.

Question 25

What are lipoproteins?

Answer 25

Most abundant protein of gram neg cells, stabilize and anchor the outer membrane to the peptidoglycan layer.

Question 26

Describe the periplasmic space.

Answer 26

Space between the outer and the cell membrane, houses the thin peptidoglycan layer, transport proteins, and hydrolytic enzymes.

Question 27

Gram positive cell wall description.

Answer 27

Thick peptidoglycan layer with one or both wall teichoic acids and lipoteichoic acids, which provide elasticity and stability.

Question 28

What are WTA and LTA anchored to?

Answer 28

WTA: peptidoglycan
LTA: cell membrane