M4: Microbial Growth

Question 1

why promote microbial growth?

Answer 1

easier to detect microbes if you have more of them within a sample

Question 2

how promote microbial growth?

Answer 2

growth media aka nutrient broth

Question 3

growth media

Answer 3

• liquid or solid formulated to support microbial growth

- contains essential nutrients (carbon/energy sources) that enable microbial expansion

Question 4

most common growth media

Answer 4

• LB media aka lysogeny broth

- nutritionally rich liquid, can grow vast array of microbes

Question 5

specialized media

Answer 5

enable researcher to control what grows & ID microorganisms

Question 6

how selective media work

Answer 6

3 methods:

1. limiting nutrients
2. varying degrees of pH
3. adding chemicals (e.g. antibiotics) that limit unwanted growth

Question 7

differential media

Answer 7

• distinguishes between two (often related microbes)

- ex. = distinguishing between E Coli and Salmonella by seeing presence/absence of lactose fermentation

Question 8

enriched media

Answer 8

• used to grow fastidious microorganisms

- contain special nutrients needed by these microorganisms

Question 9

selective media

Answer 9

• only allow certain microbes to grow
• often used in medical labs to cultivate human pathogens, esp. slow-growing ones like neisseria meningitides (potential cause of meningitis)

Question 10

fastidious microorganisms

Answer 10

microorganisms with complex growth requirements

Question 11

forms of growth media (2)

Answer 11

liquid & solid

Question 12

solid growth media

Answer 12

• often contained w/in petri dish

- simple form = liquid media and hardening agent

Question 13

agar

Answer 13

• medium-solid growth media (more agar –> firmer)
• simple growth media + polysaccharide from algae
• made by boiling agar in water –> sterile environment

Question 14

colonies

Answer 14

• microbe growth at beginning stages

- appear as isolated dots

Question 15

lawns

Answer 15

microbe growth across whole plate