1a. General Microbiology

Question 1

Which organism has exons but no introns?

Answer 1

Bacteria.

Question 2

Which bacteria has cholesterol in their membrane?

Answer 2

Mycoplasmas.

Question 3

Which organism has ergosterol in their membrane?

Answer 3

Fungi.

Question 4

What is bacterial cell wall made of?

Answer 4

Peptidoglycan.

Question 5

What is fungi cell wall made of?

Answer 5

Chitin, glucans, or mannans.

Question 6

What is the difference between bacterimia and septicemia?

Answer 6

Bacterimia: bacteria in bloodstream without overt clinical signs. Septicemia: Bacteria in bloodstream (multiplying) with clinical symptoms.

Question 7

What bacteria is common in the colon of breast-feed only babies?

Answer 7

Bifidobacterium.

Question 8

What organism produces the biofilm that glues it and other oral flora to teeth?

Answer 8

S. mutans.

Question 9

What is the primary adherence structure of gram-positive cells?

Answer 9

Teichoic acids. [Positive T :)]

Question 10

Which organism have Pili/fimbriae and what are they used for?

Answer 10

Primary adherence mechanism fo most gram-negative cells.

Question 11

Which two bacteria have the ability to adhere to inert material, producing biofilms?

Answer 11

Staph. Epidermidis, Streptococcus mutans.

Question 12

Which organism has “A protein” and what does it do?

Answer 12

Staphylococcus aureus, it is an anti-phagocytic surface component.

Question 13

What does Neisseria gonorrhoeae has to escape phagocytosis?

Answer 13

Pili.

Question 14

Which organism has “M protein” and what does it do?

Answer 14

Streptococcus pyogenes; it is an anti-phagocytic surface component.

Question 15

Which three bacteria has IgA proteases (destruction of mucosal IgA)?

Answer 15

Neisseria, Haemophilus, S. pneumoniae.

Question 16

What are invasins?

Answer 16

Surface proteins that allow an organism to bind to and invade normally non-phagocytic human cells, escaping the immune system.

Question 17

How does M. tuberculosis evade intracellular destruction?

Answer 17

By inhibiting phagosome-lysosome fusion.

Question 18

How does Listeria evade intracellular destruction?

Answer 18

By quickly escaping the phagosome into the cytoplasm BEFORE phagosome-lysosomal formation.

Question 19

What is LPS and who produces it?

Answer 19

It stands for Lipopolysaccharide (an ENDOTOXIN) and is part of the gram-negative outer membrane. The toxic portion is lipid A and generally it not relesased (and toxic) until death of cell. It is heat stable and not strongly immunogenic so it cannot be converted to a toxoid.

Question 20

Which organism releases lipid A even when the cell is not dying?

Answer 20

N. meningitidis, which over-produces outer membrane fragments.

Question 21

What are exotoxins and who produces them?

Answer 21

Are protein toxins, generally quite toxic and secreted by bacterial cells (some Gram+ and some G-).

Question 22

How come exotoxins can be processed to be used as vaccines?

Answer 22

Because they can be modified by chemicals or heat to produce a toxoid that still is immunogenic, but no longer toxic so it can be used as vaccine. It has an “A-B” component.

Question 23

What does the “B” part of the “A-B” component of exotoxin do?

Answer 23

The B component binds to specific cell receptors to facilitate the internalization of A component.

Question 24

What does the “A” part of the “A-B” component of exotoxin do?

Answer 24

The A component is the active (toxic) component (often an enzyme such as an ADP ribosyl transferase).

Question 25

What do cytolysins do?

Answer 25

Lyse cells from outside by damaging membrane.