Micro - Basic Bacteriology (Bacterial Structures & Cell Walls)

Question 1

What is the function of peptidoglycan?

Answer 1

Gives rigid support, protects against osmotic pressure

Question 2

What is the chemical composition of peptidoglycan?

Answer 2

Sugar backbone with peptide side chains cross-linked by transpeptidase

Question 3

What is the clinically relevant function of cell wall/cell membrane in gram positives versus gram negatives?

Answer 3

GRAM + = Major surface antigen; GRAM - = Major surface antigen AND Site of endotoxin (LPS)

Question 4

What is the unique substance contained in gram positive cell wall/cell membrane, and what does it induce?

Answer 4

Lipoteichoic acid, induces TNF & IL-1

Question 5

What is the unique substance contained in gram negative cell wall/cell membrane? What are its major parts, and what is the significance of each of these parts?

Answer 5

Endotoxin = LPS = Lipid A & O polysaccharide; Lipid A induces TNF & IL-1; O polysaccharide is the antigen

Question 6

For what is bacterial plasma membrane used as a site? What is the chemical composition of the bacterial plasma membrane?

Answer 6

Site of oxidative and transport enzymes; Phospholipid bilayer

Question 7

What function does the bacterial ribosome have? What is its structure?

Answer 7

Protein synthesis; 50S and 30S subunits

Question 8

What is periplasm, and in what kind of bacteria is it found? What does it contain?

Answer 8

Space between the cytoplasmic membrane and outer membrane in gram-negative bacteria; Contains many hydrolytic enzymes, including Beta-lactamases

Question 9

What function does a bacterial capsule have? What structure/composition does it typically have? What bacteria’s capsule is an exception, and what kind of structure/composition does it have?

Answer 9

Protects against phagocytosis; Polysaccharide; Except Bacillus anthracis, which contains D-glutamate

Question 10

What function do pilus/fimbria serve? More specifically, what function does a sex pilus serve? What is the structure of a pilus/fimbria?

Answer 10

Mediate adherence of bacteria to cell surface; Sex pilus forms attachment between 2 bacteria during conjugation; Glycoprotein

Question 11

What function does flagellum have? What is its structure/composition?

Answer 11

Motility; Protein

Question 12

What advantage/function do spores have? What is their structure?

Answer 12

Resistant to dehydration, heat, and chemicals; Keratin-like coat, Dipicolinic acid, Peptidoglycan

Question 13

What do plasmids contain? What is their structure?

Answer 13

Contains a variety of genes for antibiotic resistance, enzymes, and toxins; DNA

Question 14

What function does Glycocalyx have? What is its structure/composition?

Answer 14

Mediates adherence to surfaces, especially foreign surfaces (e.g., indwelling catheters); Polysaccharide

Question 15

Name 6 structures/substances that can be common to both gram-positive and gram-negative bacteria?

Answer 15

(1) Cytoplasmic membrane (2) Peptidoglycan (3) Capsule (4) Pilus (5) Flagellum (6) Cell wall (although thicker and more extensively cross linked in gram-positive bacteria)

Question 16

Name one structure/substance that is unique to gram-positive organisms.

Answer 16

Lipoteichoic acid (combination of lipids and teichoic acids)

Question 17

Name two structures/substances that are unique to gram-negative organisms.

Answer 17

(1) Endotoxin/LPS (in outer membrane) (2) Periplasm

Question 18

What advantage/function do spores have? What is their structure?

Answer 18

Resistant to dehydration, heat, and chemicals; Keratin-like coat, Dipicolinic acid, Peptidoglycan

Question 19

What do plasmids contain? What is their structure?

Answer 19

Contains a variety of genes for antibiotic resistance, enzymes, and toxins; DNA

Question 20

What function does Glycocalyx have? What is its structure/composition?

Answer 20

Mediates adherence to surfaces, especially foreign surfaces (e.g., indwelling catheters); Polysaccharide

Question 21

Name 6 structures/substances that can be common to both gram-positive and gram-negative bacteria?

Answer 21

(1) Cytoplasmic membrane (2) Peptidoglycan (3) Capsule (4) Pilus (5) Flagellum (6) Cell wall (although thicker and more extensively cross linked in gram-positive bacteria)

Question 22

Name one structure/substance that is unique to gram-positive organisms.

Answer 22

Lipoteichoic acid (combination of lipids and teichoic acids)

Question 23

Name two structures/substances that are unique to gram-negative organisms.

Answer 23

(1) Endotoxin/LPS (outer membrane) (2) Periplasm (space between cytoplasmic membrane and outer membrane in gram-negative bacteria; Contains many hydrolytic enzymes, including Beta-lactamases)