6 Laboratory Growth of Bacteria

Question 1

Name the two types of media used to grow bacteria.

Answer 1

1. Simple media

2. Complex (enriched) media

Question 2

What kind of bacteria are grown in simple media?

Answer 2

Bacteria that have v. basic nutritional needs

Question 3

What kind of bacteria are grown in enriched media?

Answer 3

Bacteria that need pre-formed nutrients for growth

Question 4

If you’re trying to grow an unknown species of bacteria, what kind of growth media would you use?

Answer 4

Complex/enriched media since you can grow a wider variety of bacteria on it.

Question 5

T or F: All bacteria can be grown in the lab.

Answer 5

F

Some bacteria have unusual/unknown growth factors and unusual environmental needs that cannot be provided in the lab.

Question 6

What are selective media?

Answer 6

Media that has additives that’re toxic to some organisms but not others > favours growth of certain organisms

Question 7

What are differential media?

Answer 7

Media that allows for the differentiation of different species based on appearance.

Question 8

MacConkey agar is both selective AND differential. What do they select for? And what can be differentiated?

Answer 8

It inhibits Gram positive bacterial growth, thus they select for Gram negative bacteria.

It differentiates b/w Gram neg. bacteria that can metabolize lactose vs. those that cannot metabolize lactose.

Question 9

How can using different types of growth media enable bacterial identification?

Answer 9

Bacteria can be identified based on their biochemical/metabolic properties within ea. medium.

Question 10

What are antibiotics?

Answer 10

Chemicals that either KILL bacteria directly or prevent them from GROWING (multiplying).

Question 11

What is the KEY characteristic that differentiates antibiotics from other antimicrobial substances?

Answer 11

Antibiotics only harm/kill bacteria, but NOT human host.

Question 12

Who came up w/ the concept of “selective toxicity”/”magic bullet” wrt antibiotics?

Answer 12

Paul Ehrlich (German dude)

Question 13

Which scientist discovered penicillin?

Answer 13

Alexander Fleming

Question 14

Term for chemicals that act specifically against bacteria.

Answer 14

Antibiotics

Question 15

4 characteristics of antibiotics?

Answer 15

1. Diff sources (natural, synthetic, and semi-synthetic)
2. Selective toxicity
3. Spectrum of activity (narrow vs. broad)
4. Cidal vs. Static effect

Question 16

This term is used to describe a type of antibiotic that kills bacteria.

Answer 16

Bactericidal

Question 17

This term is used to describe a type of antibiotic that inhibits the growth of bacteria without killing them.

Answer 17

Bacteriostatic

Question 18

T or F: Some antibiotics can act as either a cidal or static depending on dose and bacterial species.

Answer 18

T

Question 19

How exactly is selective toxicity achieved by antibiotics?

Answer 19

By acting against prokaryotic-specific processes or structures.

Question 20

List the 5 mechanisms by which antibiotics can work.

Answer 20

1. Block DNA or RNA synthesis
2. Block protein synthesis (via ribosome)
3. Inhibit metabolic pathways
4. Disrupt bacterial cell membranes
5. Block peptidoglycan synthesis

Question 21

What happens if you combine a “static” antibiotic w/ a peptidoglycan blocker antibiotic?

Answer 21

NOTHING. PG blockers only work during PG synthesis, and since “static” antibiotics prevent bacteria from multiplying, there’s no PG synthesis either.

Question 22

What do you want to achieve when using antibiotic cocktails?

Answer 22

Synergism (enhanced effect vs. either drug alone):

1. Broader spectrum of action
2. Less toxic (lower doses possible)
3. Less likelihood of resistance